# 25 Algorithms library [algorithms]

## 25.1 General [algorithms.general]

This Clause describes components that C++ programs may use to perform algorithmic operations on containers and other sequences.
The following subclauses describe components for non-modifying sequence operations, mutating sequence operations, sorting and related operations, and algorithms from the ISO C library, as summarized in [tab:algorithms.summary]Table *tab:algorithms.summary.
Table 80 — Algorithms library summary
 Subclause Header(s) [algorithms.requirements] Algorithms requirements [algorithms.parallel] Parallel algorithms [alg.nonmodifying] Non-modifying sequence operations [alg.modifying.operations] Mutating sequence operations [alg.sorting] Sorting and related operations [numeric.ops] Generalized numeric operations [alg.c.library] C library algorithms

## 25.2 Algorithms requirements [algorithms.requirements]

All of the algorithms are separated from the particular implementations of data structures and are parameterized by iterator types.
Because of this, they can work with program-defined data structures, as long as these data structures have iterator types satisfying the assumptions on the algorithms.
The entities defined in the std::ranges namespace in this Clause are not found by argument-dependent name lookup ([basic.lookup.argdep]).
When found by unqualified ([basic.lookup.unqual]) name lookup for the postfix-expression in a function call ([expr.call]), they inhibit argument-dependent name lookup.
[Example
:
void foo() {
using namespace std::ranges;
std::vector<int> vec{1,2,3};
find(begin(vec), end(vec), 2); // #1
}

The function call expression at #1 invokes std::ranges::find, not std::find, despite that (a) the iterator type returned from begin(vec) and end(vec) may be associated with namespace std and (b) std::find is more specialized ([temp.func.order]) than std::ranges::find since the former requires its first two parameters to have the same type.
end example
]
For purposes of determining the existence of data races, algorithms shall not modify objects referenced through an iterator argument unless the specification requires such modification.
Throughout this Clause, where the template parameters are not constrained, the names of template parameters are used to express type requirements.
• If an algorithm's template parameter is named InputIterator, InputIterator1, or InputIterator2, the template argument shall satisfy the Cpp17InputIterator requirements ([input.iterators]).
• If an algorithm's template parameter is named OutputIterator, OutputIterator1, or OutputIterator2, the template argument shall satisfy the Cpp17OutputIterator requirements ([output.iterators]).
• If an algorithm's template parameter is named ForwardIterator, ForwardIterator1, or ForwardIterator2, the template argument shall satisfy the Cpp17ForwardIterator requirements ([forward.iterators]).
• If an algorithm's template parameter is named BidirectionalIterator, BidirectionalIterator1, or BidirectionalIterator2, the template argument shall satisfy the Cpp17BidirectionalIterator requirements ([bidirectional.iterators]).
• If an algorithm's template parameter is named RandomAccessIterator, RandomAccessIterator1, or RandomAccessIterator2, the template argument shall satisfy the Cpp17RandomAccessIterator requirements ([random.access.iterators]).
If an algorithm's Effects: element specifies that a value pointed to by any iterator passed as an argument is modified, then that algorithm has an additional type requirement: The type of that argument shall satisfy the requirements of a mutable iterator ([iterator.requirements]).
[Note
:
This requirement does not affect arguments that are named OutputIterator, OutputIterator1, or OutputIterator2, because output iterators must always be mutable, nor does it affect arguments that are constrained, for which mutability requirements are expressed explicitly.
end note
]
Both in-place and copying versions are provided for certain algorithms.234
When such a version is provided for algorithm it is called algorithm_­copy.
Algorithms that take predicates end with the suffix _­if (which follows the suffix _­copy).
When not otherwise constrained, the Predicate parameter is used whenever an algorithm expects a function object ([function.objects]) that, when applied to the result of dereferencing the corresponding iterator, returns a value testable as true.
In other words, if an algorithm takes Predicate pred as its argument and first as its iterator argument with value type T, it should work correctly in the construct pred(*first) contextually converted to bool ([conv]).
The function object pred shall not apply any non-constant function through the dereferenced iterator.
Given a glvalue u of type (possibly const) T that designates the same object as *first, pred(u) shall be a valid expression that is equal to pred(*first).
When not otherwise constrained, the BinaryPredicate parameter is used whenever an algorithm expects a function object that when applied to the result of dereferencing two corresponding iterators or to dereferencing an iterator and type T when T is part of the signature returns a value testable as true.
In other words, if an algorithm takes BinaryPredicate binary_­pred as its argument and first1 and first2 as its iterator arguments with respective value types T1 and T2, it should work correctly in the construct binary_­pred(*first1, *first2) contextually converted to bool ([conv]).
Unless otherwise specified, BinaryPredicate always takes the first iterator's value_­type as its first argument, that is, in those cases when T value is part of the signature, it should work correctly in the construct binary_­pred(*first1, value) contextually converted to bool ([conv]).
binary_­pred shall not apply any non-constant function through the dereferenced iterators.
Given a glvalue u of type (possibly const) T1 that designates the same object as *first1, and a glvalue v of type (possibly const) T2 that designates the same object as *first2, binary_­pred(u, *first2), binary_­pred(*first1, v), and binary_­pred(u, v) shall each be a valid expression that is equal to binary_­pred(*first1, *first2), and binary_­pred(u, value) shall be a valid expression that is equal to binary_­pred(*first1, value).
The parameters UnaryOperation, BinaryOperation, BinaryOperation1, and BinaryOperation2 are used whenever an algorithm expects a function object ([function.objects]).
[Note
:
Unless otherwise specified, algorithms that take function objects as arguments are permitted to copy those function objects freely.
Programmers for whom object identity is important should consider using a wrapper class that points to a noncopied implementation object such as reference_­wrapper<T> ([refwrap]), or some equivalent solution.
end note
]
When the description of an algorithm gives an expression such as *first == value for a condition, the expression shall evaluate to either true or false in boolean contexts.
In the description of the algorithms, operator + is used for some of the iterator categories for which it does not have to be defined.
In these cases the semantics of a + n are the same as those of
auto tmp = a;
for (; n < 0; ++n) --tmp;
for (; n > 0; --n) ++tmp;
return tmp;

Similarly, operator - is used for some combinations of iterators and sentinel types for which it does not have to be defined.
If [a, b) denotes a range, the semantics of b - a in these cases are the same as those of
iter_difference_t<remove_reference_t<decltype(a)>> n = 0;
for (auto tmp = a; tmp != b; ++tmp) ++n;
return n;

and if [b, a) denotes a range, the same as those of
iter_difference_t<remove_reference_t<decltype(b)>> n = 0;
for (auto tmp = b; tmp != a; ++tmp) --n;
return n;

In the description of algorithm return values, a sentinel value s denoting the end of a range [i, s) is sometimes returned where an iterator is expected.
In these cases, the semantics are as if the sentinel is converted into an iterator using ranges::next(i, s).
Overloads of algorithms that take Range arguments ([range.range]) behave as if they are implemented by calling ranges::begin and ranges::end on the Range(s) and dispatching to the overload in namespace ranges that takes separate iterator and sentinel arguments.
The number and order of deducible template parameters for algorithm declarations are unspecified, except where explicitly stated otherwise.
[Note
:
Consequently, the algorithms may not be called with explicitly-specified template argument lists.
end note
]
The class templates binary_­transform_­result, for_­each_­result, minmax_­result, mismatch_­result, copy_­result, and partition_­copy_­result have the template parameters, data members, and special members specified below.
They have no base classes or members other than those specified.
The decision whether to include a copying version was usually based on complexity considerations.
When the cost of doing the operation dominates the cost of copy, the copying version is not included.
For example, sort_­copy is not included because the cost of sorting is much more significant, and users might as well do copy followed by sort.

## 25.3 Parallel algorithms [algorithms.parallel]

This subclause describes components that C++ programs may use to perform operations on containers and other sequences in parallel.

### 25.3.1 Terms and definitions [algorithms.parallel.defns]

A parallel algorithm is a function template listed in this document with a template parameter named ExecutionPolicy.
Parallel algorithms access objects indirectly accessible via their arguments by invoking the following functions:
• All operations of the categories of the iterators that the algorithm is instantiated with.
• Operations on those sequence elements that are required by its specification.
• User-provided function objects to be applied during the execution of the algorithm, if required by the specification.
• Operations on those function objects required by the specification.
[Note
:end note
]
These functions are herein called element access functions.
[Example
:
The sort function may invoke the following element access functions:
• Operations of the random-access iterator of the actual template argument (as per [random.access.iterators]), as implied by the name of the template parameter RandomAccessIterator.
• The swap function on the elements of the sequence (as per the preconditions specified in [sort]).
• The user-provided Compare function object.
end example
]
A standard library function is vectorization-unsafe if it is specified to synchronize with another function invocation, or another function invocation is specified to synchronize with it, and if it is not a memory allocation or deallocation function.
[Note
:
Implementations must ensure that internal synchronization inside standard library functions does not prevent forward progress when those functions are executed by threads of execution with weakly parallel forward progress guarantees.
end note
]
[Example
:
int x = 0;
std::mutex m;
void f() {
int a[] = {1,2};
std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
std::lock_guard<mutex> guard(m);            // incorrect: lock_­guard constructor calls m.lock()
++x;
});
}

The above program may result in two consecutive calls to m.lock() on the same thread of execution (which may deadlock), because the applications of the function object are not guaranteed to run on different threads of execution.
end example
]

### 25.3.2 Requirements on user-provided function objects [algorithms.parallel.user]

Unless otherwise specified, function objects passed into parallel algorithms as objects of type Predicate, BinaryPredicate, Compare, UnaryOperation, BinaryOperation, BinaryOperation1, BinaryOperation2, and the operators used by the analogous overloads to these parallel algorithms that could be formed by the invocation with the specified default predicate or operation (where applicable) shall not directly or indirectly modify objects via their arguments, nor shall they rely on the identity of the provided objects.

### 25.3.3 Effect of execution policies on algorithm execution [algorithms.parallel.exec]

Parallel algorithms have template parameters named ExecutionPolicy ([execpol]) which describe the manner in which the execution of these algorithms may be parallelized and the manner in which they apply the element access functions.
If an object is modified by an element access function, the algorithm will perform no other unsynchronized accesses to that object.
The modifying element access functions are those which are specified as modifying the object.
[Note
:
For example, swap(), ++, --, @=, and assignments modify the object.
For the assignment and @= operators, only the left argument is modified.
end note
]
Unless otherwise stated, implementations may make arbitrary copies of elements (with type T) from sequences where is_­trivially_­copy_­constructible_­v<T> and is_­trivially_­destructible_­v<T> are true.
[Note
:
This implies that user-supplied function objects should not rely on object identity of arguments for such input sequences.
Users for whom the object identity of the arguments to these function objects is important should consider using a wrapping iterator that returns a non-copied implementation object such as reference_­wrapper<T> ([refwrap]) or some equivalent solution.
end note
]
The invocations of element access functions in parallel algorithms invoked with an execution policy object of type execution::sequenced_­policy all occur in the calling thread of execution.
[Note
:
The invocations are not interleaved; see [intro.execution].
end note
]
The invocations of element access functions in parallel algorithms invoked with an execution policy object of type execution::unsequenced_­policy are permitted to execute in an unordered fashion in the calling thread of execution, unsequenced with respect to one another in the calling thread of execution.
[Note
:
This means that multiple function object invocations may be interleaved on a single thread of execution, which overrides the usual guarantee from [intro.execution] that function executions do not overlap with one another.
end note
]
The behavior of a program is undefined if it invokes a vectorization-unsafe standard library function from user code called from a execution::unsequenced_­policy algorithm.
[Note
:
Because execution::unsequenced_­policy allows the execution of element access functions to be interleaved on a single thread of execution, blocking synchronization, including the use of mutexes, risks deadlock.
end note
]
The invocations of element access functions in parallel algorithms invoked with an execution policy object of type execution::parallel_­policy are permitted to execute either in the invoking thread of execution or in a thread of execution implicitly created by the library to support parallel algorithm execution.
If the threads of execution created by thread ([thread.thread.class]) provide concurrent forward progress guarantees ([intro.progress]), then a thread of execution implicitly created by the library will provide parallel forward progress guarantees; otherwise, the provided forward progress guarantee is implementation-defined.
Any such invocations executing in the same thread of execution are indeterminately sequenced with respect to each other.
[Note
:
It is the caller's responsibility to ensure that the invocation does not introduce data races or deadlocks.
end note
]
[Example
:
int a[] = {0,1};
std::vector<int> v;
std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
v.push_back(i*2+1);                                 // incorrect: data race
});

The program above has a data race because of the unsynchronized access to the container v.
end example
]
[Example
:
std::atomic<int> x{0};
int a[] = {1,2};
std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
// spin wait for another iteration to change the value of x
while (x.load(std::memory_order::relaxed) == 1) { } // incorrect: assumes execution order
});

The above example depends on the order of execution of the iterations, and will not terminate if both iterations are executed sequentially on the same thread of execution.
end example
]
[Example
:
int x = 0;
std::mutex m;
int a[] = {1,2};
std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
std::lock_guard<mutex> guard(m);
++x;
});

The above example synchronizes access to object x ensuring that it is incremented correctly.
end example
]
The invocations of element access functions in parallel algorithms invoked with an execution policy object of type execution::parallel_­unsequenced_­policy are permitted to execute in an unordered fashion in unspecified threads of execution, and unsequenced with respect to one another within each thread of execution.
These threads of execution are either the invoking thread of execution or threads of execution implicitly created by the library; the latter will provide weakly parallel forward progress guarantees.
[Note
:
This means that multiple function object invocations may be interleaved on a single thread of execution, which overrides the usual guarantee from [intro.execution] that function executions do not overlap with one another.
end note
]
The behavior of a program is undefined if it invokes a vectorization-unsafe standard library function from user code called from a execution::parallel_­unsequenced_­policy algorithm.
[Note
:
Because execution::parallel_­unsequenced_­policy allows the execution of element access functions to be interleaved on a single thread of execution, blocking synchronization, including the use of mutexes, risks deadlock.
end note
]
[Note
:
The semantics of invocation with execution::unsequenced_­policy, execution::parallel_­policy, or execution::parallel_­unsequenced_­policy allow the implementation to fall back to sequential execution if the system cannot parallelize an algorithm invocation, e.g., due to lack of resources.
end note
]
If an invocation of a parallel algorithm uses threads of execution implicitly created by the library, then the invoking thread of execution will either
• temporarily block with forward progress guarantee delegation ([intro.progress]) on the completion of these library-managed threads of execution, or
• eventually execute an element access function;
the thread of execution will continue to do so until the algorithm is finished.
[Note
:
In blocking with forward progress guarantee delegation in this context, a thread of execution created by the library is considered to have finished execution as soon as it has finished the execution of the particular element access function that the invoking thread of execution logically depends on.
end note
]
The semantics of parallel algorithms invoked with an execution policy object of implementation-defined type are implementation-defined.

### 25.3.4 Parallel algorithm exceptions [algorithms.parallel.exceptions]

During the execution of a parallel algorithm, if temporary memory resources are required for parallelization and none are available, the algorithm throws a bad_­alloc exception.
During the execution of a parallel algorithm, if the invocation of an element access function exits via an uncaught exception, the behavior is determined by the ExecutionPolicy.

Each parallel algorithm overload has an additional template type parameter named ExecutionPolicy, which is the first template parameter.
Additionally, each parallel algorithm overload has an additional function parameter of type ExecutionPolicy&&, which is the first function parameter.
[Note
:
Not all algorithms have parallel algorithm overloads.
end note
]
Unless otherwise specified, the semantics of ExecutionPolicy algorithm overloads are identical to their overloads without.
Unless otherwise specified, the complexity requirements of ExecutionPolicy algorithm overloads are relaxed from the complexity requirements of the overloads without as follows: when the guarantee says “at most expr” or “exactly expr” and does not specify the number of assignments or swaps, and expr is not already expressed with notation, the complexity of the algorithm shall be .
Parallel algorithms shall not participate in overload resolution unless is_­execution_­policy_­v<remove_­cvref_­t<ExecutionPolicy>> is true.

## 25.4 Header <algorithm> synopsis [algorithm.syn]

#include <initializer_list>

namespace std {
// [alg.nonmodifying], non-modifying sequence operations
// [alg.all.of], all of
template<class InputIterator, class Predicate>
constexpr bool all_of(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
bool all_of(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last, Predicate pred);

namespace ranges {
template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr bool all_of(I first, S last, Pred pred, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr bool all_of(R&& r, Pred pred, Proj proj = {});
}

// [alg.any.of], any of
template<class InputIterator, class Predicate>
constexpr bool any_of(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
bool any_of(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last, Predicate pred);

namespace ranges {
template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr bool any_of(I first, S last, Pred pred, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr bool any_of(R&& r, Pred pred, Proj proj = {});
}

// [alg.none.of], none of
template<class InputIterator, class Predicate>
constexpr bool none_of(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
bool none_of(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last, Predicate pred);

namespace ranges {
template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr bool none_of(I first, S last, Pred pred, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr bool none_of(R&& r, Pred pred, Proj proj = {});
}

// [alg.foreach], for each
template<class InputIterator, class Function>
constexpr Function for_each(InputIterator first, InputIterator last, Function f);
template<class ExecutionPolicy, class ForwardIterator, class Function>
void for_each(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last, Function f);

namespace ranges {
template<class I, class F>
struct for_each_result {

template<class I2, class F2>
requires ConvertibleTo<const I&, I2> && ConvertibleTo<const F&, F2>
operator for_each_result<I2, F2>() const & {
return {in, fun};
}

template<class I2, class F2>
requires ConvertibleTo<I, I2> && ConvertibleTo<F, F2>
operator for_each_result<I2, F2>() && {
return {std::move(in), std::move(fun)};
}
};

template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryInvocable<projected<I, Proj>> Fun>
constexpr for_each_result<I, Fun>
for_each(I first, S last, Fun f, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryInvocable<projected<iterator_t<R>, Proj>> Fun>
constexpr for_each_result<safe_iterator_t<R>, Fun>
for_each(R&& r, Fun f, Proj proj = {});
}

template<class InputIterator, class Size, class Function>
constexpr InputIterator for_each_n(InputIterator first, Size n, Function f);
template<class ExecutionPolicy, class ForwardIterator, class Size, class Function>
ForwardIterator for_each_n(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, Size n, Function f);

// [alg.find], find
template<class InputIterator, class T>
constexpr InputIterator find(InputIterator first, InputIterator last,
const T& value);
template<class ExecutionPolicy, class ForwardIterator, class T>
ForwardIterator find(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
const T& value);
template<class InputIterator, class Predicate>
constexpr InputIterator find_if(InputIterator first, InputIterator last,
Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
ForwardIterator find_if(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Predicate pred);
template<class InputIterator, class Predicate>
constexpr InputIterator find_if_not(InputIterator first, InputIterator last,
Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
ForwardIterator find_if_not(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Predicate pred);

namespace ranges {
template<InputIterator I, Sentinel<I> S, class T, class Proj = identity>
requires IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*>
constexpr I find(I first, S last, const T& value, Proj proj = {});
template<InputRange R, class T, class Proj = identity>
requires IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
constexpr safe_iterator_t<R>
find(R&& r, const T& value, Proj proj = {});
template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr I find_if(I first, S last, Pred pred, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr safe_iterator_t<R>
find_if(R&& r, Pred pred, Proj proj = {});
template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr I find_if_not(I first, S last, Pred pred, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr safe_iterator_t<R>
find_if_not(R&& r, Pred pred, Proj proj = {});
}

// [alg.find.end], find end
template<class ForwardIterator1, class ForwardIterator2>
constexpr ForwardIterator1
find_end(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
constexpr ForwardIterator1
find_end(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator1
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1,
class ForwardIterator2, class BinaryPredicate>
ForwardIterator1
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);

namespace ranges {
template<ForwardIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2,
class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2>
constexpr subrange<I1>
find_end(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<ForwardRange R1, ForwardRange R2,
class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
constexpr safe_subrange_t<R1>
find_end(R1&& r1, R2&& r2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

// [alg.find.first.of], find first
template<class InputIterator, class ForwardIterator>
constexpr InputIterator
find_first_of(InputIterator first1, InputIterator last1,
ForwardIterator first2, ForwardIterator last2);
template<class InputIterator, class ForwardIterator, class BinaryPredicate>
constexpr InputIterator
find_first_of(InputIterator first1, InputIterator last1,
ForwardIterator first2, ForwardIterator last2,
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator1
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1,
class ForwardIterator2, class BinaryPredicate>
ForwardIterator1
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);

namespace ranges {
template<InputIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2,
class Proj1 = identity, class Proj2 = identity,
IndirectRelation<projected<I1, Proj1>,
projected<I2, Proj2>> Pred = ranges::equal_to>
constexpr I1 find_first_of(I1 first1, S1 last1, I2 first2, S2 last2,
Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, ForwardRange R2, class Proj1 = identity, class Proj2 = identity,
IndirectRelation<projected<iterator_t<R1>, Proj1>,
projected<iterator_t<R2>, Proj2>> Pred = ranges::equal_to>
constexpr safe_iterator_t<R1>
find_first_of(R1&& r1, R2&& r2,
Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class ForwardIterator>
constexpr ForwardIterator
template<class ForwardIterator, class BinaryPredicate>
constexpr ForwardIterator
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator
ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator, class BinaryPredicate>
ForwardIterator
ForwardIterator first, ForwardIterator last,
BinaryPredicate pred);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class Proj = identity,
IndirectRelation<projected<I, Proj>> Pred = ranges::equal_to>
constexpr I adjacent_find(I first, S last, Pred pred = {},
Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectRelation<projected<iterator_t<R>, Proj>> Pred = ranges::equal_to>
constexpr safe_iterator_t<R>
adjacent_find(R&& r, Pred pred = {}, Proj proj = {});
}

// [alg.count], count
template<class InputIterator, class T>
constexpr typename iterator_traits<InputIterator>::difference_type
count(InputIterator first, InputIterator last, const T& value);
template<class ExecutionPolicy, class ForwardIterator, class T>
typename iterator_traits<ForwardIterator>::difference_type
ForwardIterator first, ForwardIterator last, const T& value);
template<class InputIterator, class Predicate>
constexpr typename iterator_traits<InputIterator>::difference_type
count_if(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
typename iterator_traits<ForwardIterator>::difference_type
ForwardIterator first, ForwardIterator last, Predicate pred);

namespace ranges {
template<InputIterator I, Sentinel<I> S, class T, class Proj = identity>
requires IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*>
constexpr iter_difference_t<I>
count(I first, S last, const T& value, Proj proj = {});
template<InputRange R, class T, class Proj = identity>
requires IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
constexpr iter_difference_t<iterator_t<R>>
count(R&& r, const T& value, Proj proj = {});
template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr iter_difference_t<I>
count_if(I first, S last, Pred pred, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr iter_difference_t<iterator_t<R>>
count_if(R&& r, Pred pred, Proj proj = {});
}

// [mismatch], mismatch
template<class InputIterator1, class InputIterator2>
constexpr pair<InputIterator1, InputIterator2>
mismatch(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2);
template<class InputIterator1, class InputIterator2, class BinaryPredicate>
constexpr pair<InputIterator1, InputIterator2>
mismatch(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, BinaryPredicate pred);
template<class InputIterator1, class InputIterator2>
constexpr pair<InputIterator1, InputIterator2>
mismatch(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2);
template<class InputIterator1, class InputIterator2, class BinaryPredicate>
constexpr pair<InputIterator1, InputIterator2>
mismatch(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
pair<ForwardIterator1, ForwardIterator2>
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class BinaryPredicate>
pair<ForwardIterator1, ForwardIterator2>
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
pair<ForwardIterator1, ForwardIterator2>
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class BinaryPredicate>
pair<ForwardIterator1, ForwardIterator2>
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);

namespace ranges {
template<class I1, class I2>
struct mismatch_result {

template<class II1, class II2>
requires ConvertibleTo<const I1&, II1> && ConvertibleTo<const I2&, II2>
operator mismatch_result<II1, II2>() const & {
return {in1, in2};
}

template<class II1, class II2>
requires ConvertibleTo<I1, II1> && ConvertibleTo<I2, II2>
operator mismatch_result<II1, II2>() && {
return {std::move(in1), std::move(in2)};
}
};

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
class Proj1 = identity, class Proj2 = identity,
IndirectRelation<projected<I1, Proj1>,
projected<I2, Proj2>> Pred = ranges::equal_to>
constexpr mismatch_result<I1, I2>
mismatch(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2,
class Proj1 = identity, class Proj2 = identity,
IndirectRelation<projected<iterator_t<R1>, Proj1>,
projected<iterator_t<R2>, Proj2>> Pred = ranges::equal_to>
constexpr mismatch_result<safe_iterator_t<R1>, safe_iterator_t<R2>>
mismatch(R1&& r1, R2&& r2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

// [alg.equal], equal
template<class InputIterator1, class InputIterator2>
constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2);
template<class InputIterator1, class InputIterator2, class BinaryPredicate>
constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, BinaryPredicate pred);
template<class InputIterator1, class InputIterator2>
constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2);
template<class InputIterator1, class InputIterator2, class BinaryPredicate>
constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
bool equal(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class BinaryPredicate>
bool equal(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
bool equal(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class BinaryPredicate>
bool equal(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);

namespace ranges {
template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2>
constexpr bool equal(I1 first1, S1 last1, I2 first2, S2 last2,
Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, class Pred = ranges::equal_to,
class Proj1 = identity, class Proj2 = identity>
requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
constexpr bool equal(R1&& r1, R2&& r2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

// [alg.is.permutation], is permutation
template<class ForwardIterator1, class ForwardIterator2>
constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2);
template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, BinaryPredicate pred);
template<class ForwardIterator1, class ForwardIterator2>
constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);

namespace ranges {
template<ForwardIterator I1, Sentinel<I1> S1, ForwardIterator I2,
Sentinel<I2> S2, class Pred = ranges::equal_to, class Proj1 = identity,
class Proj2 = identity>
requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2>
constexpr bool is_permutation(I1 first1, S1 last1, I2 first2, S2 last2,
Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<ForwardRange R1, ForwardRange R2, class Pred = ranges::equal_to,
class Proj1 = identity, class Proj2 = identity>
requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
constexpr bool is_permutation(R1&& r1, R2&& r2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

// [alg.search], search
template<class ForwardIterator1, class ForwardIterator2>
constexpr ForwardIterator1
search(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
constexpr ForwardIterator1
search(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator1
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class BinaryPredicate>
ForwardIterator1
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);

namespace ranges {
template<ForwardIterator I1, Sentinel<I1> S1, ForwardIterator I2,
Sentinel<I2> S2, class Pred = ranges::equal_to,
class Proj1 = identity, class Proj2 = identity>
requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2>
constexpr subrange<I1>
search(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<ForwardRange R1, ForwardRange R2, class Pred = ranges::equal_to,
class Proj1 = identity, class Proj2 = identity>
requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
constexpr safe_subrange_t<R1>
search(R1&& r1, R2&& r2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class ForwardIterator, class Size, class T>
constexpr ForwardIterator
search_n(ForwardIterator first, ForwardIterator last,
Size count, const T& value);
template<class ForwardIterator, class Size, class T, class BinaryPredicate>
constexpr ForwardIterator
search_n(ForwardIterator first, ForwardIterator last,
Size count, const T& value,
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Size, class T>
ForwardIterator
ForwardIterator first, ForwardIterator last,
Size count, const T& value);
template<class ExecutionPolicy, class ForwardIterator, class Size, class T,
class BinaryPredicate>
ForwardIterator
ForwardIterator first, ForwardIterator last,
Size count, const T& value,
BinaryPredicate pred);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class T,
class Pred = ranges::equal_to, class Proj = identity>
requires IndirectlyComparable<I, const T*, Pred, Proj>
constexpr subrange<I>
search_n(I first, S last, iter_difference_t<I> count,
const T& value, Pred pred = {}, Proj proj = {});
template<ForwardRange R, class T, class Pred = ranges::equal_to,
class Proj = identity>
requires IndirectlyComparable<iterator_t<R>, const T*, Pred, Proj>
constexpr safe_subrange_t<R>
search_n(R&& r, iter_difference_t<iterator_t<R>> count,
const T& value, Pred pred = {}, Proj proj = {});
}

template<class ForwardIterator, class Searcher>
constexpr ForwardIterator
search(ForwardIterator first, ForwardIterator last, const Searcher& searcher);

// [alg.modifying.operations], mutating sequence operations
// [alg.copy], copy
template<class InputIterator, class OutputIterator>
constexpr OutputIterator copy(InputIterator first, InputIterator last,
OutputIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator2 copy(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result);

namespace ranges {
template<class I, class O>
struct copy_result {

template<class I2, class O2>
requires ConvertibleTo<const I&, I2> && ConvertibleTo<const O&, O2>
operator copy_result<I2, O2>() const & {
return {in, out};
}

template<class I2, class O2>
requires ConvertibleTo<I, I2> && ConvertibleTo<O, O2>
operator copy_result<I2, O2>() && {
return {std::move(in), std::move(out)};
}
};

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O>
requires IndirectlyCopyable<I, O>
constexpr copy_result<I, O>
copy(I first, S last, O result);
template<InputRange R, WeaklyIncrementable O>
requires IndirectlyCopyable<iterator_t<R>, O>
constexpr copy_result<safe_iterator_t<R>, O>
copy(R&& r, O result);
}

template<class InputIterator, class Size, class OutputIterator>
constexpr OutputIterator copy_n(InputIterator first, Size n,
OutputIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class Size,
class ForwardIterator2>
ForwardIterator2 copy_n(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first, Size n,
ForwardIterator2 result);

namespace ranges {
template<class I, class O>
using copy_n_result = copy_result<I, O>;

template<InputIterator I, WeaklyIncrementable O>
requires IndirectlyCopyable<I, O>
constexpr copy_n_result<I, O>
copy_n(I first, iter_difference_t<I> n, O result);
}

template<class InputIterator, class OutputIterator, class Predicate>
constexpr OutputIterator copy_if(InputIterator first, InputIterator last,
OutputIterator result, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class Predicate>
ForwardIterator2 copy_if(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result, Predicate pred);

namespace ranges {
template<class I, class O>
using copy_if_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
requires IndirectlyCopyable<I, O>
constexpr copy_if_result<I, O>
copy_if(I first, S last, O result, Pred pred, Proj proj = {});
template<InputRange R, WeaklyIncrementable O, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires IndirectlyCopyable<iterator_t<R>, O>
constexpr copy_if_result<safe_iterator_t<R>, O>
copy_if(R&& r, O result, Pred pred, Proj proj = {});
}

template<class BidirectionalIterator1, class BidirectionalIterator2>
constexpr BidirectionalIterator2
copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last,
BidirectionalIterator2 result);

namespace ranges {
template<class I1, class I2>
using copy_backward_result = copy_result<I1, I2>;

template<BidirectionalIterator I1, Sentinel<I1> S1, BidirectionalIterator I2>
requires IndirectlyCopyable<I1, I2>
constexpr copy_backward_result<I1, I2>
copy_backward(I1 first, S1 last, I2 result);
template<BidirectionalRange R, BidirectionalIterator I>
requires IndirectlyCopyable<iterator_t<R>, I>
constexpr copy_backward_result<safe_iterator_t<R>, I>
copy_backward(R&& r, I result);
}

// [alg.move], move
template<class InputIterator, class OutputIterator>
constexpr OutputIterator move(InputIterator first, InputIterator last,
OutputIterator result);
template<class ExecutionPolicy, class ForwardIterator1,
class ForwardIterator2>
ForwardIterator2 move(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result);

namespace ranges {
template<class I, class O>
using move_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O>
requires IndirectlyMovable<I, O>
constexpr move_result<I, O>
move(I first, S last, O result);
template<InputRange R, WeaklyIncrementable O>
requires IndirectlyMovable<iterator_t<R>, O>
constexpr move_result<safe_iterator_t<R>, O>
move(R&& r, O result);
}

template<class BidirectionalIterator1, class BidirectionalIterator2>
constexpr BidirectionalIterator2
move_backward(BidirectionalIterator1 first, BidirectionalIterator1 last,
BidirectionalIterator2 result);

namespace ranges {
template<class I1, class I2>
using move_backward_result = copy_result<I1, I2>;

template<BidirectionalIterator I1, Sentinel<I1> S1, BidirectionalIterator I2>
requires IndirectlyMovable<I1, I2>
constexpr move_backward_result<I1, I2>
move_backward(I1 first, S1 last, I2 result);
template<BidirectionalRange R, BidirectionalIterator I>
requires IndirectlyMovable<iterator_t<R>, I>
constexpr move_backward_result<safe_iterator_t<R>, I>
move_backward(R&& r, I result);
}

// [alg.swap], swap
template<class ForwardIterator1, class ForwardIterator2>
constexpr ForwardIterator2 swap_ranges(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator2 swap_ranges(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2);

namespace ranges {
template<class I1, class I2>
using swap_ranges_result = mismatch_result<I1, I2>;

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2>
requires IndirectlySwappable<I1, I2>
constexpr swap_ranges_result<I1, I2>
swap_ranges(I1 first1, S1 last1, I2 first2, S2 last2);
template<InputRange R1, InputRange R2>
requires IndirectlySwappable<iterator_t<R1>, iterator_t<R2>>
constexpr swap_ranges_result<safe_iterator_t<R1>, safe_iterator_t<R2>>
swap_ranges(R1&& r1, R2&& r2);
}

template<class ForwardIterator1, class ForwardIterator2>
constexpr void iter_swap(ForwardIterator1 a, ForwardIterator2 b);

// [alg.transform], transform
template<class InputIterator, class OutputIterator, class UnaryOperation>
constexpr OutputIterator
transform(InputIterator first1, InputIterator last1,
OutputIterator result, UnaryOperation op);
template<class InputIterator1, class InputIterator2, class OutputIterator,
class BinaryOperation>
constexpr OutputIterator
transform(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, OutputIterator result,
BinaryOperation binary_op);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class UnaryOperation>
ForwardIterator2
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 result, UnaryOperation op);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator, class BinaryOperation>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator result,
BinaryOperation binary_op);

namespace ranges {
template<class I, class O>
using unary_transform_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O,
CopyConstructible F, class Proj = identity>
requires Writable<O, indirect_result_t<F&, projected<I, Proj>>>
constexpr unary_transform_result<I, O>
transform(I first1, S last1, O result, F op, Proj proj = {});
template<InputRange R, WeaklyIncrementable O, CopyConstructible F,
class Proj = identity>
requires Writable<O, indirect_result_t<F&, projected<iterator_t<R>, Proj>>>
constexpr unary_transform_result<safe_iterator_t<R>, O>
transform(R&& r, O result, F op, Proj proj = {});

template<class I1, class I2, class O>
struct binary_transform_result {

template<class II1, class II2, class OO>
requires ConvertibleTo<const I1&, II1> &&
ConvertibleTo<const I2&, II2> && ConvertibleTo<const O&, OO>
operator binary_transform_result<II1, II2, OO>() const & {
return {in1, in2, out};
}

template<class II1, class II2, class OO>
requires ConvertibleTo<I1, II1> &&
ConvertibleTo<I2, II2> && ConvertibleTo<O, OO>
operator binary_transform_result<II1, II2, OO>() && {
return {std::move(in1), std::move(in2), std::move(out)};
}
};

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
WeaklyIncrementable O, CopyConstructible F, class Proj1 = identity,
class Proj2 = identity>
requires Writable<O, indirect_result_t<F&, projected<I1, Proj1>,
projected<I2, Proj2>>>
constexpr binary_transform_result<I1, I2, O>
transform(I1 first1, S1 last1, I2 first2, S2 last2, O result,
F binary_op, Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, WeaklyIncrementable O,
CopyConstructible F, class Proj1 = identity, class Proj2 = identity>
requires Writable<O, indirect_result_t<F&, projected<iterator_t<R1>, Proj1>,
projected<iterator_t<R2>, Proj2>>>
constexpr binary_transform_result<safe_iterator_t<R1>, safe_iterator_t<R2>, O>
transform(R1&& r1, R2&& r2, O result,
F binary_op, Proj1 proj1 = {}, Proj2 proj2 = {});
}

// [alg.replace], replace
template<class ForwardIterator, class T>
constexpr void replace(ForwardIterator first, ForwardIterator last,
const T& old_value, const T& new_value);
template<class ExecutionPolicy, class ForwardIterator, class T>
void replace(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
const T& old_value, const T& new_value);
template<class ForwardIterator, class Predicate, class T>
constexpr void replace_if(ForwardIterator first, ForwardIterator last,
Predicate pred, const T& new_value);
template<class ExecutionPolicy, class ForwardIterator, class Predicate, class T>
void replace_if(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Predicate pred, const T& new_value);

namespace ranges {
template<InputIterator I, Sentinel<I> S, class T1, class T2, class Proj = identity>
requires Writable<I, const T2&> &&
IndirectRelation<ranges::equal_to, projected<I, Proj>, const T1*>
constexpr I
replace(I first, S last, const T1& old_value, const T2& new_value, Proj proj = {});
template<InputRange R, class T1, class T2, class Proj = identity>
requires Writable<iterator_t<R>, const T2&> &&
IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T1*>
constexpr safe_iterator_t<R>
replace(R&& r, const T1& old_value, const T2& new_value, Proj proj = {});
template<InputIterator I, Sentinel<I> S, class T, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
requires Writable<I, const T&>
constexpr I replace_if(I first, S last, Pred pred, const T& new_value, Proj proj = {});
template<InputRange R, class T, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires Writable<iterator_t<R>, const T&>
constexpr safe_iterator_t<R>
replace_if(R&& r, Pred pred, const T& new_value, Proj proj = {});
}

template<class InputIterator, class OutputIterator, class T>
constexpr OutputIterator replace_copy(InputIterator first, InputIterator last,
OutputIterator result,
const T& old_value, const T& new_value);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class T>
ForwardIterator2 replace_copy(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result,
const T& old_value, const T& new_value);
template<class InputIterator, class OutputIterator, class Predicate, class T>
constexpr OutputIterator replace_copy_if(InputIterator first, InputIterator last,
OutputIterator result,
Predicate pred, const T& new_value);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class Predicate, class T>
ForwardIterator2 replace_copy_if(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result,
Predicate pred, const T& new_value);

namespace ranges {
template<class I, class O>
using replace_copy_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, class T1, class T2, OutputIterator<const T2&> O,
class Proj = identity>
requires IndirectlyCopyable<I, O> &&
IndirectRelation<ranges::equal_to, projected<I, Proj>, const T1*>
constexpr replace_copy_result<I, O>
replace_copy(I first, S last, O result, const T1& old_value, const T2& new_value,
Proj proj = {});
template<InputRange R, class T1, class T2, OutputIterator<const T2&> O,
class Proj = identity>
requires IndirectlyCopyable<iterator_t<R>, O> &&
IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T1*>
constexpr replace_copy_result<safe_iterator_t<R>, O>
replace_copy(R&& r, O result, const T1& old_value, const T2& new_value,
Proj proj = {});

template<class I, class O>
using replace_copy_if_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, class T, OutputIterator<const T&> O,
class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred>
requires IndirectlyCopyable<I, O>
constexpr replace_copy_if_result<I, O>
replace_copy_if(I first, S last, O result, Pred pred, const T& new_value,
Proj proj = {});
template<InputRange R, class T, OutputIterator<const T&> O, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires IndirectlyCopyable<iterator_t<R>, O>
constexpr replace_copy_if_result<safe_iterator_t<R>, O>
replace_copy_if(R&& r, O result, Pred pred, const T& new_value,
Proj proj = {});
}

// [alg.fill], fill
template<class ForwardIterator, class T>
constexpr void fill(ForwardIterator first, ForwardIterator last, const T& value);
template<class ExecutionPolicy, class ForwardIterator, class T>
void fill(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last, const T& value);
template<class OutputIterator, class Size, class T>
constexpr OutputIterator fill_n(OutputIterator first, Size n, const T& value);
template<class ExecutionPolicy, class ForwardIterator,
class Size, class T>
ForwardIterator fill_n(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, Size n, const T& value);

namespace ranges {
template<class T, OutputIterator<const T&> O, Sentinel<O> S>
constexpr O fill(O first, S last, const T& value);
template<class T, OutputRange<const T&> R>
constexpr safe_iterator_t<R> fill(R&& r, const T& value);
template<class T, OutputIterator<const T&> O>
constexpr O fill_n(O first, iter_difference_t<O> n, const T& value);
}

// [alg.generate], generate
template<class ForwardIterator, class Generator>
constexpr void generate(ForwardIterator first, ForwardIterator last,
Generator gen);
template<class ExecutionPolicy, class ForwardIterator, class Generator>
void generate(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Generator gen);
template<class OutputIterator, class Size, class Generator>
constexpr OutputIterator generate_n(OutputIterator first, Size n, Generator gen);
template<class ExecutionPolicy, class ForwardIterator, class Size, class Generator>
ForwardIterator generate_n(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, Size n, Generator gen);

namespace ranges {
template<Iterator O, Sentinel<O> S, CopyConstructible F>
requires Invocable<F&> && Writable<O, invoke_result_t<F&>>
constexpr O generate(O first, S last, F gen);
template<class R, CopyConstructible F>
requires Invocable<F&> && OutputRange<R, invoke_result_t<F&>>
constexpr safe_iterator_t<R> generate(R&& r, F gen);
template<Iterator O, CopyConstructible F>
requires Invocable<F&> && Writable<O, invoke_result_t<F&>>
constexpr O generate_n(O first, iter_difference_t<O> n, F gen);
}

// [alg.remove], remove
template<class ForwardIterator, class T>
constexpr ForwardIterator remove(ForwardIterator first, ForwardIterator last,
const T& value);
template<class ExecutionPolicy, class ForwardIterator, class T>
ForwardIterator remove(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
const T& value);
template<class ForwardIterator, class Predicate>
constexpr ForwardIterator remove_if(ForwardIterator first, ForwardIterator last,
Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
ForwardIterator remove_if(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Predicate pred);

namespace ranges {
template<Permutable I, Sentinel<I> S, class T, class Proj = identity>
requires IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*>
constexpr I remove(I first, S last, const T& value, Proj proj = {});
template<ForwardRange R, class T, class Proj = identity>
requires Permutable<iterator_t<R>> &&
IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
constexpr safe_iterator_t<R>
remove(R&& r, const T& value, Proj proj = {});
template<Permutable I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr I remove_if(I first, S last, Pred pred, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires Permutable<iterator_t<R>>
constexpr safe_iterator_t<R>
remove_if(R&& r, Pred pred, Proj proj = {});
}

template<class InputIterator, class OutputIterator, class T>
constexpr OutputIterator
remove_copy(InputIterator first, InputIterator last,
OutputIterator result, const T& value);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class T>
ForwardIterator2
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result, const T& value);
template<class InputIterator, class OutputIterator, class Predicate>
constexpr OutputIterator
remove_copy_if(InputIterator first, InputIterator last,
OutputIterator result, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class Predicate>
ForwardIterator2
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result, Predicate pred);

namespace ranges {
template<class I, class O>
using remove_copy_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, class T,
class Proj = identity>
requires IndirectlyCopyable<I, O> &&
IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*>
constexpr remove_copy_result<I, O>
remove_copy(I first, S last, O result, const T& value, Proj proj = {});
template<InputRange R, WeaklyIncrementable O, class T, class Proj = identity>
requires IndirectlyCopyable<iterator_t<R>, O> &&
IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
constexpr remove_copy_result<safe_iterator_t<R>, O>
remove_copy(R&& r, O result, const T& value, Proj proj = {});

template<class I, class O>
using remove_copy_if_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O,
class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred>
requires IndirectlyCopyable<I, O>
constexpr remove_copy_if_result<I, O>
remove_copy_if(I first, S last, O result, Pred pred, Proj proj = {});
template<InputRange R, WeaklyIncrementable O, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires IndirectlyCopyable<iterator_t<R>, O>
constexpr remove_copy_if_result<safe_iterator_t<R>, O>
remove_copy_if(R&& r, O result, Pred pred, Proj proj = {});
}

// [alg.unique], unique
template<class ForwardIterator>
constexpr ForwardIterator unique(ForwardIterator first, ForwardIterator last);
template<class ForwardIterator, class BinaryPredicate>
constexpr ForwardIterator unique(ForwardIterator first, ForwardIterator last,
BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator unique(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator, class BinaryPredicate>
ForwardIterator unique(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
BinaryPredicate pred);

namespace ranges {
template<Permutable I, Sentinel<I> S, class Proj = identity,
IndirectRelation<projected<I, Proj>> C = ranges::equal_to>
constexpr I unique(I first, S last, C comp = {}, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectRelation<projected<iterator_t<R>, Proj>> C = ranges::equal_to>
requires Permutable<iterator_t<R>>
constexpr safe_iterator_t<R>
unique(R&& r, C comp = {}, Proj proj = {});
}

template<class InputIterator, class OutputIterator>
constexpr OutputIterator
unique_copy(InputIterator first, InputIterator last,
OutputIterator result);
template<class InputIterator, class OutputIterator, class BinaryPredicate>
constexpr OutputIterator
unique_copy(InputIterator first, InputIterator last,
OutputIterator result, BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator2
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class BinaryPredicate>
ForwardIterator2
ForwardIterator1 first, ForwardIterator1 last,
ForwardIterator2 result, BinaryPredicate pred);

namespace ranges {
template<class I, class O>
using unique_copy_result = copy_result<I, O>;

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O,
class Proj = identity, IndirectRelation<projected<I, Proj>> C = ranges::equal_to>
requires IndirectlyCopyable<I, O> &&
(ForwardIterator<I> ||
(InputIterator<O> && Same<iter_value_t<I>, iter_value_t<O>>) ||
IndirectlyCopyableStorable<I, O>)
constexpr unique_copy_result<I, O>
unique_copy(I first, S last, O result, C comp = {}, Proj proj = {});
template<InputRange R, WeaklyIncrementable O, class Proj = identity,
IndirectRelation<projected<iterator_t<R>, Proj>> C = ranges::equal_to>
requires IndirectlyCopyable<iterator_t<R>, O> &&
(ForwardIterator<iterator_t<R>> ||
(InputIterator<O> && Same<iter_value_t<iterator_t<R>>, iter_value_t<O>>) ||
IndirectlyCopyableStorable<iterator_t<R>, O>)
constexpr unique_copy_result<safe_iterator_t<R>, O>
unique_copy(R&& r, O result, C comp = {}, Proj proj = {});
}

// [alg.reverse], reverse
template<class BidirectionalIterator>
constexpr void reverse(BidirectionalIterator first, BidirectionalIterator last);
template<class ExecutionPolicy, class BidirectionalIterator>
void reverse(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
BidirectionalIterator first, BidirectionalIterator last);

namespace ranges {
template<BidirectionalIterator I, Sentinel<I> S>
requires Permutable<I>
constexpr I reverse(I first, S last);
template<BidirectionalRange R>
requires Permutable<iterator_t<R>>
constexpr safe_iterator_t<R> reverse(R&& r);
}

template<class BidirectionalIterator, class OutputIterator>
constexpr OutputIterator
reverse_copy(BidirectionalIterator first, BidirectionalIterator last,
OutputIterator result);
template<class ExecutionPolicy, class BidirectionalIterator, class ForwardIterator>
ForwardIterator
BidirectionalIterator first, BidirectionalIterator last,
ForwardIterator result);

namespace ranges {
template<class I, class O>
using reverse_copy_result = copy_result<I, O>;

template<BidirectionalIterator I, Sentinel<I> S, WeaklyIncrementable O>
requires IndirectlyCopyable<I, O>
constexpr reverse_copy_result<I, O>
reverse_copy(I first, S last, O result);
template<BidirectionalRange R, WeaklyIncrementable O>
requires IndirectlyCopyable<iterator_t<R>, O>
constexpr reverse_copy_result<safe_iterator_t<R>, O>
reverse_copy(R&& r, O result);
}

// [alg.rotate], rotate
template<class ForwardIterator>
constexpr ForwardIterator rotate(ForwardIterator first,
ForwardIterator middle,
ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator rotate(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first,
ForwardIterator middle,
ForwardIterator last);

namespace ranges {
template<Permutable I, Sentinel<I> S>
constexpr subrange<I> rotate(I first, I middle, S last);
template<ForwardRange R>
requires Permutable<iterator_t<R>>
constexpr safe_subrange_t<R> rotate(R&& r, iterator_t<R> middle);
}

template<class ForwardIterator, class OutputIterator>
constexpr OutputIterator
rotate_copy(ForwardIterator first, ForwardIterator middle,
ForwardIterator last, OutputIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
ForwardIterator2
ForwardIterator1 first, ForwardIterator1 middle,
ForwardIterator1 last, ForwardIterator2 result);

namespace ranges {
template<class I, class O>
using rotate_copy_result = copy_result<I, O>;

template<ForwardIterator I, Sentinel<I> S, WeaklyIncrementable O>
requires IndirectlyCopyable<I, O>
constexpr rotate_copy_result<I, O>
rotate_copy(I first, I middle, S last, O result);
template<ForwardRange R, WeaklyIncrementable O>
requires IndirectlyCopyable<iterator_t<R>, O>
constexpr rotate_copy_result<safe_iterator_t<R>, O>
rotate_copy(R&& r, iterator_t<R> middle, O result);
}

// [alg.random.sample], sample
template<class PopulationIterator, class SampleIterator,
class Distance, class UniformRandomBitGenerator>
SampleIterator sample(PopulationIterator first, PopulationIterator last,
SampleIterator out, Distance n,
UniformRandomBitGenerator&& g);

// [alg.random.shuffle], shuffle
template<class RandomAccessIterator, class UniformRandomBitGenerator>
void shuffle(RandomAccessIterator first,
RandomAccessIterator last,
UniformRandomBitGenerator&& g);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Gen>
requires Permutable<I> &&
UniformRandomBitGenerator<remove_reference_t<Gen>> &&
ConvertibleTo<invoke_result_t<Gen&>, iter_difference_t<I>>
I shuffle(I first, S last, Gen&& g);
template<RandomAccessRange R, class Gen>
requires Permutable<iterator_t<R>> &&
UniformRandomBitGenerator<remove_reference_t<Gen>> &&
ConvertibleTo<invoke_result_t<Gen&>, iter_difference_t<iterator_t<R>>>
safe_iterator_t<R> shuffle(R&& r, Gen&& g);
}

// [alg.shift], shift
template<class ForwardIterator>
constexpr ForwardIterator
shift_left(ForwardIterator first, ForwardIterator last,
typename iterator_traits<ForwardIterator>::difference_type n);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator
ForwardIterator first, ForwardIterator last,
typename iterator_traits<ForwardIterator>::difference_type n);
template<class ForwardIterator>
constexpr ForwardIterator
shift_right(ForwardIterator first, ForwardIterator last,
typename iterator_traits<ForwardIterator>::difference_type n);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator
ForwardIterator first, ForwardIterator last,
typename iterator_traits<ForwardIterator>::difference_type n);

// [alg.sorting], sorting and related operations
// [alg.sort], sorting
template<class RandomAccessIterator>
constexpr void sort(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void sort(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator>
void sort(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
void sort(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr I
sort(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr safe_iterator_t<R>
sort(R&& r, Comp comp = {}, Proj proj = {});
}

template<class RandomAccessIterator>
void stable_sort(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
void stable_sort(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator>
void stable_sort(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
void stable_sort(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
I stable_sort(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
safe_iterator_t<R>
stable_sort(R&& r, Comp comp = {}, Proj proj = {});
}

template<class RandomAccessIterator>
constexpr void partial_sort(RandomAccessIterator first,
RandomAccessIterator middle,
RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void partial_sort(RandomAccessIterator first,
RandomAccessIterator middle,
RandomAccessIterator last, Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator>
void partial_sort(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first,
RandomAccessIterator middle,
RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
void partial_sort(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first,
RandomAccessIterator middle,
RandomAccessIterator last, Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr I
partial_sort(I first, I middle, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr safe_iterator_t<R>
partial_sort(R&& r, iterator_t<R> middle, Comp comp = {},
Proj proj = {});
}

template<class InputIterator, class RandomAccessIterator>
constexpr RandomAccessIterator
partial_sort_copy(InputIterator first, InputIterator last,
RandomAccessIterator result_first,
RandomAccessIterator result_last);
template<class InputIterator, class RandomAccessIterator, class Compare>
constexpr RandomAccessIterator
partial_sort_copy(InputIterator first, InputIterator last,
RandomAccessIterator result_first,
RandomAccessIterator result_last,
Compare comp);
template<class ExecutionPolicy, class ForwardIterator, class RandomAccessIterator>
RandomAccessIterator
ForwardIterator first, ForwardIterator last,
RandomAccessIterator result_first,
RandomAccessIterator result_last);
template<class ExecutionPolicy, class ForwardIterator, class RandomAccessIterator,
class Compare>
RandomAccessIterator
ForwardIterator first, ForwardIterator last,
RandomAccessIterator result_first,
RandomAccessIterator result_last,
Compare comp);

namespace ranges {
template<InputIterator I1, Sentinel<I1> S1, RandomAccessIterator I2, Sentinel<I2> S2,
class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
requires IndirectlyCopyable<I1, I2> && Sortable<I2, Comp, Proj2> &&
IndirectStrictWeakOrder<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
constexpr I2
partial_sort_copy(I1 first, S1 last, I2 result_first, S2 result_last,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, RandomAccessRange R2, class Comp = ranges::less,
class Proj1 = identity, class Proj2 = identity>
requires IndirectlyCopyable<iterator_t<R1>, iterator_t<R2>> &&
Sortable<iterator_t<R2>, Comp, Proj2> &&
IndirectStrictWeakOrder<Comp, projected<iterator_t<R1>, Proj1>,
projected<iterator_t<R2>, Proj2>>
constexpr safe_iterator_t<R2>
partial_sort_copy(R1&& r, R2&& result_r, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class ForwardIterator>
constexpr bool is_sorted(ForwardIterator first, ForwardIterator last);
template<class ForwardIterator, class Compare>
constexpr bool is_sorted(ForwardIterator first, ForwardIterator last,
Compare comp);
template<class ExecutionPolicy, class ForwardIterator>
bool is_sorted(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator, class Compare>
bool is_sorted(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class Proj = identity,
IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less>
constexpr bool is_sorted(I first, S last, Comp comp = {}, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
constexpr bool is_sorted(R&& r, Comp comp = {}, Proj proj = {});
}

template<class ForwardIterator>
constexpr ForwardIterator
is_sorted_until(ForwardIterator first, ForwardIterator last);
template<class ForwardIterator, class Compare>
constexpr ForwardIterator
is_sorted_until(ForwardIterator first, ForwardIterator last,
Compare comp);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator
ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator, class Compare>
ForwardIterator
ForwardIterator first, ForwardIterator last,
Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class Proj = identity,
IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less>
constexpr I is_sorted_until(I first, S last, Comp comp = {}, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
constexpr safe_iterator_t<R>
is_sorted_until(R&& r, Comp comp = {}, Proj proj = {});
}

// [alg.nth.element], Nth element
template<class RandomAccessIterator>
constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last, Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator>
void nth_element(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
void nth_element(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last, Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr I
nth_element(I first, I nth, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr safe_iterator_t<R>
nth_element(R&& r, iterator_t<R> nth, Comp comp = {}, Proj proj = {});
}

// [alg.binary.search], binary search
template<class ForwardIterator, class T>
constexpr ForwardIterator
lower_bound(ForwardIterator first, ForwardIterator last,
const T& value);
template<class ForwardIterator, class T, class Compare>
constexpr ForwardIterator
lower_bound(ForwardIterator first, ForwardIterator last,
const T& value, Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<I, Proj>> Comp = ranges::less>
constexpr I lower_bound(I first, S last, const T& value, Comp comp = {},
Proj proj = {});
template<ForwardRange R, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<iterator_t<R>, Proj>> Comp =
ranges::less>
constexpr safe_iterator_t<R>
lower_bound(R&& r, const T& value, Comp comp = {}, Proj proj = {});
}

template<class ForwardIterator, class T>
constexpr ForwardIterator
upper_bound(ForwardIterator first, ForwardIterator last,
const T& value);
template<class ForwardIterator, class T, class Compare>
constexpr ForwardIterator
upper_bound(ForwardIterator first, ForwardIterator last,
const T& value, Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<I, Proj>> Comp = ranges::less>
constexpr I upper_bound(I first, S last, const T& value, Comp comp = {}, Proj proj = {});
template<ForwardRange R, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<iterator_t<R>, Proj>> Comp =
ranges::less>
constexpr safe_iterator_t<R>
upper_bound(R&& r, const T& value, Comp comp = {}, Proj proj = {});
}

template<class ForwardIterator, class T>
constexpr pair<ForwardIterator, ForwardIterator>
equal_range(ForwardIterator first, ForwardIterator last,
const T& value);
template<class ForwardIterator, class T, class Compare>
constexpr pair<ForwardIterator, ForwardIterator>
equal_range(ForwardIterator first, ForwardIterator last,
const T& value, Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<I, Proj>> Comp = ranges::less>
constexpr subrange<I>
equal_range(I first, S last, const T& value, Comp comp = {}, Proj proj = {});
template<ForwardRange R, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<iterator_t<R>, Proj>> Comp =
ranges::less>
constexpr safe_subrange_t<R>
equal_range(R&& r, const T& value, Comp comp = {}, Proj proj = {});
}

template<class ForwardIterator, class T>
constexpr bool
binary_search(ForwardIterator first, ForwardIterator last,
const T& value);
template<class ForwardIterator, class T, class Compare>
constexpr bool
binary_search(ForwardIterator first, ForwardIterator last,
const T& value, Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<I, Proj>> Comp = ranges::less>
constexpr bool binary_search(I first, S last, const T& value, Comp comp = {},
Proj proj = {});
template<ForwardRange R, class T, class Proj = identity,
IndirectStrictWeakOrder<const T*, projected<iterator_t<R>, Proj>> Comp =
ranges::less>
constexpr bool binary_search(R&& r, const T& value, Comp comp = {},
Proj proj = {});
}

// [alg.partitions], partitions
template<class InputIterator, class Predicate>
constexpr bool is_partitioned(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
bool is_partitioned(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last, Predicate pred);

namespace ranges {
template<InputIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr bool is_partitioned(I first, S last, Pred pred, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr bool is_partitioned(R&& r, Pred pred, Proj proj = {});
}

template<class ForwardIterator, class Predicate>
constexpr ForwardIterator partition(ForwardIterator first,
ForwardIterator last,
Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
ForwardIterator partition(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first,
ForwardIterator last,
Predicate pred);

namespace ranges {
template<Permutable I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr I
partition(I first, S last, Pred pred, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires Permutable<iterator_t<R>>
constexpr safe_iterator_t<R>
partition(R&& r, Pred pred, Proj proj = {});
}

template<class BidirectionalIterator, class Predicate>
BidirectionalIterator stable_partition(BidirectionalIterator first,
BidirectionalIterator last,
Predicate pred);
template<class ExecutionPolicy, class BidirectionalIterator, class Predicate>
BidirectionalIterator stable_partition(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
BidirectionalIterator first,
BidirectionalIterator last,
Predicate pred);

namespace ranges {
template<BidirectionalIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
requires Permutable<I>
I stable_partition(I first, S last, Pred pred, Proj proj = {});
template<BidirectionalRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires Permutable<iterator_t<R>>
safe_iterator_t<R> stable_partition(R&& r, Pred pred, Proj proj = {});
}

template<class InputIterator, class OutputIterator1,
class OutputIterator2, class Predicate>
constexpr pair<OutputIterator1, OutputIterator2>
partition_copy(InputIterator first, InputIterator last,
OutputIterator1 out_true, OutputIterator2 out_false,
Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class ForwardIterator1,
class ForwardIterator2, class Predicate>
pair<ForwardIterator1, ForwardIterator2>
ForwardIterator first, ForwardIterator last,
ForwardIterator1 out_true, ForwardIterator2 out_false,
Predicate pred);

namespace ranges {
template<class I, class O1, class O2>
struct partition_copy_result {

template<class II, class OO1, class OO2>
requires ConvertibleTo<const I&, II> &&
ConvertibleTo<const O1&, OO1> && ConvertibleTo<const O2&, OO2>
operator partition_copy_result<II, OO1, OO2>() const & {
return {in, out1, out2};
}

template<class II, class OO1, class OO2>
requires ConvertibleTo<I, II> &&
ConvertibleTo<O1, OO1> && ConvertibleTo<O2, OO2>
operator partition_copy_result<II, OO1, OO2>() && {
return {std::move(in), std::move(out1), std::move(out2)};
}
};

template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O1, WeaklyIncrementable O2,
class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred>
requires IndirectlyCopyable<I, O1> && IndirectlyCopyable<I, O2>
constexpr partition_copy_result<I, O1, O2>
partition_copy(I first, S last, O1 out_true, O2 out_false, Pred pred,
Proj proj = {});
template<InputRange R, WeaklyIncrementable O1, WeaklyIncrementable O2,
class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
requires IndirectlyCopyable<iterator_t<R>, O1> &&
IndirectlyCopyable<iterator_t<R>, O2>
constexpr partition_copy_result<safe_iterator_t<R>, O1, O2>
partition_copy(R&& r, O1 out_true, O2 out_false, Pred pred, Proj proj = {});
}

template<class ForwardIterator, class Predicate>
constexpr ForwardIterator
partition_point(ForwardIterator first, ForwardIterator last,
Predicate pred);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class Proj = identity,
IndirectUnaryPredicate<projected<I, Proj>> Pred>
constexpr I partition_point(I first, S last, Pred pred, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred>
constexpr safe_iterator_t<R>
partition_point(R&& r, Pred pred, Proj proj = {});
}

// [alg.merge], merge
template<class InputIterator1, class InputIterator2, class OutputIterator>
constexpr OutputIterator
merge(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template<class InputIterator1, class InputIterator2, class OutputIterator,
class Compare>
constexpr OutputIterator
merge(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator, class Compare>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result, Compare comp);

namespace ranges {
template<class I1, class I2, class O>
using merge_result = binary_transform_result<I1, I2, O>;

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
WeaklyIncrementable O, class Comp = ranges::less, class Proj1 = identity,
class Proj2 = identity>
requires Mergeable<I1, I2, O, Comp, Proj1, Proj2>
constexpr merge_result<I1, I2, O>
merge(I1 first1, S1 last1, I2 first2, S2 last2, O result,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, WeaklyIncrementable O, class Comp = ranges::less,
class Proj1 = identity, class Proj2 = identity>
requires Mergeable<iterator_t<R1>, iterator_t<R2>, O, Comp, Proj1, Proj2>
constexpr merge_result<safe_iterator_t<R1>, safe_iterator_t<R2>, O>
merge(R1&& r1, R2&& r2, O result,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class BidirectionalIterator>
void inplace_merge(BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last);
template<class BidirectionalIterator, class Compare>
void inplace_merge(BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last, Compare comp);
template<class ExecutionPolicy, class BidirectionalIterator>
void inplace_merge(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last);
template<class ExecutionPolicy, class BidirectionalIterator, class Compare>
void inplace_merge(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last, Compare comp);

namespace ranges {
template<BidirectionalIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
I inplace_merge(I first, I middle, S last, Comp comp = {}, Proj proj = {});
template<BidirectionalRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
safe_iterator_t<R>
inplace_merge(R&& r, iterator_t<R> middle, Comp comp = {},
Proj proj = {});
}

// [alg.set.operations], set operations
template<class InputIterator1, class InputIterator2>
constexpr bool includes(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2);
template<class InputIterator1, class InputIterator2, class Compare>
constexpr bool includes(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
Compare comp);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
bool includes(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class Compare>
bool includes(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
Compare comp);

namespace ranges {
template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
class Proj1 = identity, class Proj2 = identity,
IndirectStrictWeakOrder<projected<I1, Proj1>, projected<I2, Proj2>> Comp =
ranges::less>
constexpr bool includes(I1 first1, S1 last1, I2 first2, S2 last2, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, class Proj1 = identity,
class Proj2 = identity,
IndirectStrictWeakOrder<projected<iterator_t<R1>, Proj1>,
projected<iterator_t<R2>, Proj2>> Comp = ranges::less>
constexpr bool includes(R1&& r1, R2&& r2, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class InputIterator1, class InputIterator2, class OutputIterator>
constexpr OutputIterator
set_union(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template<class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
constexpr OutputIterator
set_union(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator, class Compare>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result, Compare comp);

namespace ranges {
template<class I1, class I2, class O>
using set_union_result = binary_transform_result<I1, I2, O>;

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
WeaklyIncrementable O, class Comp = ranges::less,
class Proj1 = identity, class Proj2 = identity>
requires Mergeable<I1, I2, O, Comp, Proj1, Proj2>
constexpr set_union_result<I1, I2, O>
set_union(I1 first1, S1 last1, I2 first2, S2 last2, O result, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, WeaklyIncrementable O,
class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
requires Mergeable<iterator_t<R1>, iterator_t<R2>, O, Comp, Proj1, Proj2>
constexpr set_union_result<safe_iterator_t<R1>, safe_iterator_t<R2>, O>
set_union(R1&& r1, R2&& r2, O result, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class InputIterator1, class InputIterator2, class OutputIterator>
constexpr OutputIterator
set_intersection(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template<class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
constexpr OutputIterator
set_intersection(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator, class Compare>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result, Compare comp);

namespace ranges {
template<class I1, class I2, class O>
using set_intersection_result = binary_transform_result<I1, I2, O>;

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
WeaklyIncrementable O, class Comp = ranges::less,
class Proj1 = identity, class Proj2 = identity>
requires Mergeable<I1, I2, O, Comp, Proj1, Proj2>
constexpr set_intersection_result<I1, I2, O>
set_intersection(I1 first1, S1 last1, I2 first2, S2 last2, O result,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, WeaklyIncrementable O,
class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
requires Mergeable<iterator_t<R1>, iterator_t<R2>, O, Comp, Proj1, Proj2>
constexpr set_intersection_result<safe_iterator_t<R1>, safe_iterator_t<R2>, O>
set_intersection(R1&& r1, R2&& r2, O result,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class InputIterator1, class InputIterator2, class OutputIterator>
constexpr OutputIterator
set_difference(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template<class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
constexpr OutputIterator
set_difference(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator, class Compare>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result, Compare comp);

namespace ranges {
template<class I, class O>
using set_difference_result = copy_result<I, O>;

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
WeaklyIncrementable O, class Comp = ranges::less,
class Proj1 = identity, class Proj2 = identity>
requires Mergeable<I1, I2, O, Comp, Proj1, Proj2>
constexpr set_difference_result<I1, O>
set_difference(I1 first1, S1 last1, I2 first2, S2 last2, O result,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, WeaklyIncrementable O,
class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
requires Mergeable<iterator_t<R1>, iterator_t<R2>, O, Comp, Proj1, Proj2>
constexpr set_difference_result<safe_iterator_t<R1>, O>
set_difference(R1&& r1, R2&& r2, O result,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
}

template<class InputIterator1, class InputIterator2, class OutputIterator>
constexpr OutputIterator
set_symmetric_difference(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template<class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
constexpr OutputIterator
set_symmetric_difference(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class ForwardIterator, class Compare>
ForwardIterator
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
ForwardIterator result, Compare comp);

namespace ranges {
template<class I1, class I2, class O>
using set_symmetric_difference_result = binary_transform_result<I1, I2, O>;

template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
WeaklyIncrementable O, class Comp = ranges::less,
class Proj1 = identity, class Proj2 = identity>
requires Mergeable<I1, I2, O, Comp, Proj1, Proj2>
constexpr set_symmetric_difference_result<I1, I2, O>
set_symmetric_difference(I1 first1, S1 last1, I2 first2, S2 last2, O result,
Comp comp = {}, Proj1 proj1 = {},
Proj2 proj2 = {});
template<InputRange R1, InputRange R2, WeaklyIncrementable O,
class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
requires Mergeable<iterator_t<R1>, iterator_t<R2>, O, Comp, Proj1, Proj2>
constexpr set_symmetric_difference_result<safe_iterator_t<R1>, safe_iterator_t<R2>, O>
set_symmetric_difference(R1&& r1, R2&& r2, O result, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

// [alg.heap.operations], heap operations
template<class RandomAccessIterator>
constexpr void push_heap(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void push_heap(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr I
push_heap(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr safe_iterator_t<R>
push_heap(R&& r, Comp comp = {}, Proj proj = {});
}

template<class RandomAccessIterator>
constexpr void pop_heap(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void pop_heap(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr I
pop_heap(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr safe_iterator_t<R>
pop_heap(R&& r, Comp comp = {}, Proj proj = {});
}

template<class RandomAccessIterator>
constexpr void make_heap(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void make_heap(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr I
make_heap(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr safe_iterator_t<R>
make_heap(R&& r, Comp comp = {}, Proj proj = {});
}

template<class RandomAccessIterator>
constexpr void sort_heap(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void sort_heap(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr I
sort_heap(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr safe_iterator_t<R>
sort_heap(R&& r, Comp comp = {}, Proj proj = {});
}

template<class RandomAccessIterator>
constexpr bool is_heap(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr bool is_heap(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator>
bool is_heap(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
bool is_heap(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Proj = identity,
IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less>
constexpr bool is_heap(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
constexpr bool is_heap(R&& r, Comp comp = {}, Proj proj = {});
}

template<class RandomAccessIterator>
constexpr RandomAccessIterator
is_heap_until(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr RandomAccessIterator
is_heap_until(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator>
RandomAccessIterator
RandomAccessIterator first, RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
RandomAccessIterator
RandomAccessIterator first, RandomAccessIterator last,
Compare comp);

namespace ranges {
template<RandomAccessIterator I, Sentinel<I> S, class Proj = identity,
IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less>
constexpr I is_heap_until(I first, S last, Comp comp = {}, Proj proj = {});
template<RandomAccessRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
constexpr safe_iterator_t<R>
is_heap_until(R&& r, Comp comp = {}, Proj proj = {});
}

// [alg.min.max], minimum and maximum
template<class T> constexpr const T& min(const T& a, const T& b);
template<class T, class Compare>
constexpr const T& min(const T& a, const T& b, Compare comp);
template<class T>
constexpr T min(initializer_list<T> t);
template<class T, class Compare>
constexpr T min(initializer_list<T> t, Compare comp);

namespace ranges {
template<class T, class Proj = identity,
IndirectStrictWeakOrder<projected<const T*, Proj>> Comp = ranges::less>
constexpr const T& min(const T& a, const T& b, Comp comp = {}, Proj proj = {});
template<Copyable T, class Proj = identity,
IndirectStrictWeakOrder<projected<const T*, Proj>> Comp = ranges::less>
constexpr T min(initializer_list<T> r, Comp comp = {}, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
requires IndirectlyCopyableStorable<iterator_t<R>, iter_value_t<iterator_t<R>>*>
constexpr iter_value_t<iterator_t<R>>
min(R&& r, Comp comp = {}, Proj proj = {});
}

template<class T> constexpr const T& max(const T& a, const T& b);
template<class T, class Compare>
constexpr const T& max(const T& a, const T& b, Compare comp);
template<class T>
constexpr T max(initializer_list<T> t);
template<class T, class Compare>
constexpr T max(initializer_list<T> t, Compare comp);

namespace ranges {
template<class T, class Proj = identity,
IndirectStrictWeakOrder<projected<const T*, Proj>> Comp = ranges::less>
constexpr const T& max(const T& a, const T& b, Comp comp = {}, Proj proj = {});
template<Copyable T, class Proj = identity,
IndirectStrictWeakOrder<projected<const T*, Proj>> Comp = ranges::less>
constexpr T max(initializer_list<T> r, Comp comp = {}, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
requires IndirectlyCopyableStorable<iterator_t<R>, iter_value_t<iterator_t<R>>*>
constexpr iter_value_t<iterator_t<R>>
max(R&& r, Comp comp = {}, Proj proj = {});
}

template<class T> constexpr pair<const T&, const T&> minmax(const T& a, const T& b);
template<class T, class Compare>
constexpr pair<const T&, const T&> minmax(const T& a, const T& b, Compare comp);
template<class T>
constexpr pair<T, T> minmax(initializer_list<T> t);
template<class T, class Compare>
constexpr pair<T, T> minmax(initializer_list<T> t, Compare comp);

namespace ranges {
template<class T>
struct minmax_result {

template<class T2>
requires ConvertibleTo<const T&, T2>
operator minmax_result<T2>() const & {
return {min, max};
}

template<class T2>
requires ConvertibleTo<T, T2>
operator minmax_result<T2>() && {
return {std::move(min), std::move(max)};
}
};

template<class T, class Proj = identity,
IndirectStrictWeakOrder<projected<const T*, Proj>> Comp = ranges::less>
constexpr minmax_result<const T&>
minmax(const T& a, const T& b, Comp comp = {}, Proj proj = {});
template<Copyable T, class Proj = identity,
IndirectStrictWeakOrder<projected<const T*, Proj>> Comp = ranges::less>
constexpr minmax_result<T>
minmax(initializer_list<T> r, Comp comp = {}, Proj proj = {});
template<InputRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
requires IndirectlyCopyableStorable<iterator_t<R>, iter_value_t<iterator_t<R>>*>
constexpr minmax_result<iter_value_t<iterator_t<R>>>
minmax(R&& r, Comp comp = {}, Proj proj = {});
}

template<class ForwardIterator>
constexpr ForwardIterator min_element(ForwardIterator first, ForwardIterator last);
template<class ForwardIterator, class Compare>
constexpr ForwardIterator min_element(ForwardIterator first, ForwardIterator last,
Compare comp);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator min_element(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator, class Compare>
ForwardIterator min_element(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class Proj = identity,
IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less>
constexpr I min_element(I first, S last, Comp comp = {}, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
constexpr safe_iterator_t<R>
min_element(R&& r, Comp comp = {}, Proj proj = {});
}

template<class ForwardIterator>
constexpr ForwardIterator max_element(ForwardIterator first, ForwardIterator last);
template<class ForwardIterator, class Compare>
constexpr ForwardIterator max_element(ForwardIterator first, ForwardIterator last,
Compare comp);
template<class ExecutionPolicy, class ForwardIterator>
ForwardIterator max_element(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator, class Compare>
ForwardIterator max_element(ExecutionPolicy&& exec, // see [algorithms.parallel.overloads]
ForwardIterator first, ForwardIterator last,
Compare comp);

namespace ranges {
template<ForwardIterator I, Sentinel<I> S, class Proj = identity,
IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less>
constexpr I max_element(I first, S last, Comp comp = {}, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
constexpr safe_iterator_t<R>
max_element(R&& r, Comp comp = {}, Proj proj = {});
}

template<class ForwardIterator>
constexpr pair<ForwardIterator, ForwardIterator>
minmax_element(ForwardIterator first, ForwardIterator last);
template<class ForwardIterator, class Compare>
constexpr pair<ForwardIterator, ForwardIterator>
minmax_element(ForwardIterator first, ForwardIterator last, Compare comp);
template<class ExecutionPolicy, class ForwardIterator>
pair<ForwardIterator, ForwardIterator>
ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator, class Compare>
pair<ForwardIterator, ForwardIterator>
ForwardIterator first, ForwardIterator last, Compare comp);

namespace ranges {
template<class I>
using minmax_element_result = minmax_result<I>;

template<ForwardIterator I, Sentinel<I> S, class Proj = identity,
IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less>
constexpr minmax_element_result<I>
minmax_element(I first, S last, Comp comp = {}, Proj proj = {});
template<ForwardRange R, class Proj = identity,
IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less>
constexpr minmax_element_result<safe_iterator_t<R>>
minmax_element(R&& r, Comp comp = {}, Proj proj = {});
}

// [alg.clamp], bounded value
template<class T>
constexpr const T& clamp(const T& v, const T& lo, const T& hi);
template<class T, class Compare>
constexpr const T& clamp(const T& v, const T& lo, const T& hi, Compare comp);

// [alg.lex.comparison], lexicographical comparison
template<class InputIterator1, class InputIterator2>
constexpr bool
lexicographical_compare(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2);
template<class InputIterator1, class InputIterator2, class Compare>
constexpr bool
lexicographical_compare(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
Compare comp);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
bool
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
class Compare>
bool
ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
Compare comp);

namespace ranges {
template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2,
class Proj1 = identity, class Proj2 = identity,
IndirectStrictWeakOrder<projected<I1, Proj1>, projected<I2, Proj2>> Comp =
ranges::less>
constexpr bool
lexicographical_compare(I1 first1, S1 last1, I2 first2, S2 last2,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
template<InputRange R1, InputRange R2, class Proj1 = identity,
class Proj2 = identity,
IndirectStrictWeakOrder<projected<iterator_t<R1>, Proj1>,
projected<iterator_t<R2>, Proj2>> Comp = ranges::less>
constexpr bool
lexicographical_compare(R1&& r1, R2&& r2, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {});
}

// [alg.3way], three-way comparison algorithms
template<class T, class U>
constexpr auto compare_3way(const T& a, const U& b);
template<class InputIterator1, class InputIterator2, class Cmp>
constexpr auto
lexicographical_compare_3way(InputIterator1 b1, InputIterator1 e1,
InputIterator2 b2, InputIterator2 e2,
Cmp comp)
-> common_comparison_category_t<decltype(comp(*b1, *b2)), strong_ordering>;
template<class InputIterator1, class InputIterator2>
constexpr auto
lexicographical_compare_3way(InputIterator1 b1, InputIterator1 e1,
InputIterator2 b2, InputIterator2 e2);

// [alg.permutation.generators], permutations
template<class BidirectionalIterator>
constexpr bool next_permutation(BidirectionalIterator first,
BidirectionalIterator last);
template<class BidirectionalIterator, class Compare>
constexpr bool next_permutation(BidirectionalIterator first,
BidirectionalIterator last, Compare comp);

namespace ranges {
template<BidirectionalIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr bool
next_permutation(I first, S last, Comp comp = {}, Proj proj = {});
template<BidirectionalRange R, class Comp = ranges::less,
class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr bool
next_permutation(R&& r, Comp comp = {}, Proj proj = {});
}

template<class BidirectionalIterator>
constexpr bool prev_permutation(BidirectionalIterator first,
BidirectionalIterator last);
template<class BidirectionalIterator, class Compare>
constexpr bool prev_permutation(BidirectionalIterator first,
BidirectionalIterator last, Compare comp);

namespace ranges {
template<BidirectionalIterator I, Sentinel<I> S, class Comp = ranges::less,
class Proj = identity>
requires Sortable<I, Comp, Proj>
constexpr bool
prev_permutation(I first, S last, Comp comp = {}, Proj proj = {});
template<BidirectionalRange R, class Comp = ranges::less,
class Proj = identity>
requires Sortable<iterator_t<R>, Comp, Proj>
constexpr bool
prev_permutation(R&& r, Comp comp = {}, Proj proj = {});
}
}


## 25.5 Non-modifying sequence operations [alg.nonmodifying]

### 25.5.1 All of [alg.all.of]

template<class InputIterator, class Predicate> constexpr bool all_of(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> bool all_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<InputIterator I, Sentinel<I> S, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> constexpr bool ranges::all_of(I first, S last, Pred pred, Proj proj = {}); template<InputRange R, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> constexpr bool ranges::all_of(R&& r, Pred pred, Proj proj = {}); 
Let E be pred(*i) and invoke(pred, invoke(proj, *i)) for the overloads in namespace std and std::ranges, respectively.
Returns: false if E is false for some iterator i in the range [first, last), and true otherwise.
Complexity: At most last - first applications of the predicate and any projection.

### 25.5.2 Any of [alg.any.of]

template<class InputIterator, class Predicate> constexpr bool any_of(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> bool any_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<InputIterator I, Sentinel<I> S, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> constexpr bool ranges::any_of(I first, S last, Pred pred, Proj proj = {}); template<InputRange R, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> constexpr bool ranges::any_of(R&& r, Pred pred, Proj proj = {}); 
Let E be pred(*i) and invoke(pred, invoke(proj, *i)) for the overloads in namespace std and std::ranges, respectively.
Returns: true if E is true for some iterator i in the range [first, last), and false otherwise.
Complexity: At most last - first applications of the predicate and any projection.

### 25.5.3 None of [alg.none.of]

template<class InputIterator, class Predicate> constexpr bool none_of(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> bool none_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<InputIterator I, Sentinel<I> S, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> constexpr bool ranges::none_of(I first, S last, Pred pred, Proj proj = {}); template<InputRange R, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> constexpr bool ranges::none_of(R&& r, Pred pred, Proj proj = {}); 
Let E be pred(*i) and invoke(pred, invoke(proj, *i)) for the overloads in namespace std and std::ranges, respectively.
Returns: false if E is true for some iterator i in the range [first, last), and true otherwise.
Complexity: At most last - first applications of the predicate and any projection.

### 25.5.4 For each [alg.foreach]

template<class InputIterator, class Function> constexpr Function for_each(InputIterator first, InputIterator last, Function f); 
Requires: Function shall satisfy the Cpp17MoveConstructible requirements ([tab:moveconstructible]Table *tab:moveconstructible).
[Note
:
Function need not meet the requirements of Cpp17CopyConstructible ([tab:copyconstructible]Table *tab:copyconstructible).
end note
]
Effects: Applies f to the result of dereferencing every iterator in the range [first, last), starting from first and proceeding to last - 1.
[Note
:
If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.
end note
]
Returns: f.
Complexity: Applies f exactly last - first times.
Remarks: If f returns a result, the result is ignored.
template<class ExecutionPolicy, class ForwardIterator, class Function> void for_each(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Function f); 
Requires: Function shall satisfy the Cpp17CopyConstructible requirements.
Effects: Applies f to the result of dereferencing every iterator in the range [first, last).
[Note
:
If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.
end note
]
Complexity: Applies f exactly last - first times.
Remarks: If f returns a result, the result is ignored.
Implementations do not have the freedom granted under [algorithms.parallel.exec] to make arbitrary copies of elements from the input sequence.
[Note
:
Does not return a copy of its Function parameter, since parallelization may not permit efficient state accumulation.
end note
]
template<InputIterator I, Sentinel<I> S, class Proj = identity, IndirectUnaryInvocable<projected<I, Proj>> Fun> constexpr ranges::for_each_result<I, Fun> ranges::for_each(I first, S last, Fun f, Proj proj = {}); template<InputRange R, class Proj = identity, IndirectUnaryInvocable<projected<iterator_t<R>, Proj>> Fun> constexpr ranges::for_each_result<safe_iterator_t<R>, Fun> ranges::for_each(R&& r, Fun f, Proj proj = {}); 
Effects: Calls invoke(f, invoke(proj, *i)) for every iterator i in the range [first, last), starting from first and proceeding to last - 1.
[Note
:
If the result of invoke(proj, *i) is a mutable reference, f may apply non-constant functions.
end note
]
Returns: {last, std::move(f)}.
Complexity: Applies f and proj exactly last - first times.
Remarks: If f returns a result, the result is ignored.
[Note
:
The overloads in namespace ranges require Fun to model CopyConstructible.
end note
]
template<class InputIterator, class Size, class Function> constexpr InputIterator for_each_n(InputIterator first, Size n, Function f); 
Requires: Function shall satisfy the Cpp17MoveConstructible requirements
[Note
:
Function need not meet the requirements of Cpp17CopyConstructible.
end note
]
Requires: n >= 0.
Effects: Applies f to the result of dereferencing every iterator in the range [first, first + n) in order.
[Note
:
If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.
end note
]
Returns: first + n.
Remarks: If f returns a result, the result is ignored.
template<class ExecutionPolicy, class ForwardIterator, class Size, class Function> ForwardIterator for_each_n(ExecutionPolicy&& exec, ForwardIterator first, Size n, Function f); 
Requires: Function shall satisfy the Cpp17CopyConstructible requirements.
Requires: n >= 0.
Effects: Applies f to the result of dereferencing every iterator in the range [first, first + n).
[Note
:
If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.
end note
]
Returns: first + n.
Remarks: If f returns a result, the result is ignored.
Implementations do not have the freedom granted under [algorithms.parallel.exec] to make arbitrary copies of elements from the input sequence.

### 25.5.5 Find [alg.find]

template<class InputIterator, class T> constexpr InputIterator find(InputIterator first, InputIterator last, const T& value); template<class ExecutionPolicy, class ForwardIterator, class T> ForwardIterator find(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& value); template<class InputIterator, class Predicate> constexpr InputIterator find_if(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> ForwardIterator find_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<class InputIterator, class Predicate> constexpr InputIterator find_if_not(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> ForwardIterator find_if_not(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<InputIterator I, Sentinel<I> S, class T, class Proj = identity> requires IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*> constexpr I ranges::find(I first, S last, const T& value, Proj proj = {}); template<InputRange R, class T, class Proj = identity> requires IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> constexpr safe_iterator_t<R> ranges::find(R&& r, const T& value, Proj proj = {}); template<InputIterator I, Sentinel<I> S, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> constexpr I ranges::find_if(I first, S last, Pred pred, Proj proj = {}); template<InputRange R, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> constexpr safe_iterator_t<R> ranges::find_if(R&& r, Pred pred, Proj proj = {}); template<InputIterator I, Sentinel<I> S, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> constexpr I ranges::find_if_not(I first, S last, Pred pred, Proj proj = {}); template<InputRange R, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> constexpr safe_iterator_t<R> ranges::find_if_not(R&& r, Pred pred, Proj proj = {}); 
Let E be:
• *i == value for find,
• pred(*i) != false for find_­if,
• pred(*i) == false for find_­if_­not,
• invoke(proj, *i) == value for ranges::find,
• invoke(pred, invoke(proj, *i)) != false for ranges::find_­if,
• invoke(pred, invoke(proj, *i)) == false for ranges::find_­if_­not.
Returns: The first iterator i in the range [first, last) for which E is true.
Returns last if no such iterator is found.
Complexity: At most last - first applications of the corresponding predicate and any projection.

### 25.5.6 Find end [alg.find.end]

template<class ForwardIterator1, class ForwardIterator2> constexpr ForwardIterator1 find_end(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator1 find_end(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> constexpr ForwardIterator1 find_end(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 find_end(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<ForwardIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2> constexpr subrange<I1> ranges::find_end(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<ForwardRange R1, ForwardRange R2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2> constexpr safe_subrange_t<R1> ranges::find_end(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Let:
• pred be equal_­to{} for the overloads with no parameter pred.
• E be:
• pred(*(i + n), *(first2 + n)) for the overloads in namespace std,
• invoke(pred, invoke(proj1, *(i + n)), invoke(proj2, *(first2 + n))) for the overloads in namespace ranges.
• i be last1 if [first2, last2) is empty, or if (last2 - first2) > (last1 - first1) is true, or if there is no iterator in the range [first1, last1 - (last2 - first2)) such that for every non-negative integer n < (last2 - first2), E is true.
Otherwise i is the last such iterator in [first1, last1 - (last2 - first2)).
Returns:
• i for the overloads in namespace std, and
• {i, i + (i == last1 ? 0 : last2 - first2)} for the overloads in namespace ranges.
Complexity: At most (last2 - first2) * (last1 - first1 - (last2 - first2) + 1) applications of the corresponding predicate and any projections.

### 25.5.7 Find first [alg.find.first.of]

template<class InputIterator, class ForwardIterator> constexpr InputIterator find_first_of(InputIterator first1, InputIterator last1, ForwardIterator first2, ForwardIterator last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator1 find_first_of(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class InputIterator, class ForwardIterator, class BinaryPredicate> constexpr InputIterator find_first_of(InputIterator first1, InputIterator last1, ForwardIterator first2, ForwardIterator last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 find_first_of(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<InputIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2, class Proj1 = identity, class Proj2 = identity, IndirectRelation<projected<I1, Proj1>, projected<I2, Proj2>> Pred = ranges::equal_to> constexpr I1 ranges::find_first_of(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<InputRange R1, ForwardRange R2, class Proj1 = identity, class Proj2 = identity, IndirectRelation<projected<iterator_t<R1>, Proj1>, projected<iterator_t<R2>, Proj2>> Pred = ranges::equal_to> constexpr safe_iterator_t<R1> ranges::find_first_of(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Let E be:
• *i == *j for the overloads with no parameter pred,
• pred(*i, *j) != false for the overloads with a parameter pred and no parameter proj1,
• invoke(pred, invoke(proj1, *i), invoke(proj2, *j)) != false for the overloads with parameters pred and proj1.
Effects: Finds an element that matches one of a set of values.
Returns: The first iterator i in the range [first1, last1) such that for some iterator j in the range [first2, last2) E holds.
Returns last1 if [first2, last2) is empty or if no such iterator is found.
Complexity: At most (last1-first1) * (last2-first2) applications of the corresponding predicate and any projections.

template<class ForwardIterator> constexpr ForwardIterator adjacent_find(ForwardIterator first, ForwardIterator last); template<class ExecutionPolicy, class ForwardIterator> ForwardIterator adjacent_find(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last); template<class ForwardIterator, class BinaryPredicate> constexpr ForwardIterator adjacent_find(ForwardIterator first, ForwardIterator last, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator, class BinaryPredicate> ForwardIterator adjacent_find(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, BinaryPredicate pred); template<ForwardIterator I, Sentinel<I> S, class Proj = identity, IndirectRelation<projected<I, Proj>> Pred = ranges::equal_to> constexpr I ranges::adjacent_find(I first, S last, Pred pred = {}, Proj proj = {}); template<ForwardRange R, class Proj = identity, IndirectRelation<projected<iterator_t<R>, Proj>> Pred = ranges::equal_to> constexpr safe_iterator_t<R> ranges::adjacent_find(R&& r, Pred pred = {}, Proj proj = {}); 
Let E be:
• *i == *(i + 1) for the overloads with no parameter pred,
• pred(*i, *(i + 1)) != false for the overloads with a parameter pred and no parameter proj,
• invoke(pred, invoke(proj, *i), invoke(proj, *(i + 1))) != false for the overloads with both parameters pred and proj.
Returns: The first iterator i such that both i and i + 1 are in the range [first, last) for which E holds.
Returns last if no such iterator is found.
Complexity: For the overloads with no ExecutionPolicy, exactly
applications of the corresponding predicate, where i is adjacent_­find's return value.
For the overloads with an ExecutionPolicy, applications of the corresponding predicate, and no more than twice as many applications of any projection.

### 25.5.9 Count [alg.count]

template<class InputIterator, class T> constexpr typename iterator_traits<InputIterator>::difference_type count(InputIterator first, InputIterator last, const T& value); template<class ExecutionPolicy, class ForwardIterator, class T> typename iterator_traits<ForwardIterator>::difference_type count(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& value); template<class InputIterator, class Predicate> constexpr typename iterator_traits<InputIterator>::difference_type count_if(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> typename iterator_traits<ForwardIterator>::difference_type count_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<InputIterator I, Sentinel<I> S, class T, class Proj = identity> requires IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*> constexpr iter_difference_t<I> ranges::count(I first, S last, const T& value, Proj proj = {}); template<InputRange R, class T, class Proj = identity> requires IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> constexpr iter_difference_t<iterator_t<R>> ranges::count(R&& r, const T& value, Proj proj = {}); template<InputIterator I, Sentinel<I> S, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> constexpr iter_difference_t<I> ranges::count_if(I first, S last, Pred pred, Proj proj = {}); template<InputRange R, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> constexpr iter_difference_t<iterator_t<R>> ranges::count_if(R&& r, Pred pred, Proj proj = {}); 
Let E be:
• *i == value for the overloads with no parameter pred or proj,
• pred(*i) != false for the overloads with a parameter pred but no parameter proj,
• invoke(proj, *i) == value for the overloads with a parameter proj but no parameter pred,
• invoke(pred, invoke(proj, *i)) != false for the overloads with both parameters proj and pred.
Effects: Returns the number of iterators i in the range [first, last) for which E holds.
Complexity: Exactly last - first applications of the corresponding predicate and any projection.

### 25.5.10 Mismatch [mismatch]

template<class InputIterator1, class InputIterator2> constexpr pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> constexpr pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, BinaryPredicate pred); template<class InputIterator1, class InputIterator2> constexpr pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> constexpr pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2, class Proj1 = identity, class Proj2 = identity, IndirectRelation<projected<I1, Proj1>, projected<I2, Proj2>> Pred = ranges::equal_to> constexpr ranges::mismatch_result<I1, I2> ranges::mismatch(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<InputRange R1, InputRange R2, class Proj1 = identity, class Proj2 = identity, IndirectRelation<projected<iterator_t<R1>, Proj1>, projected<iterator_t<R2>, Proj2>> Pred = ranges::equal_to> constexpr ranges::mismatch_result<safe_iterator_t<R1>, safe_iterator_t<R2>> ranges::mismatch(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Let last2 be first2 + (last1 - first1) for the overloads with no parameter last2 or r2.
Let E be:
• !(*(first1 + n) == *(first2 + n)) for the overloads with no parameter pred,
• pred(*(first1 + n), *(first2 + n)) == false for the overloads with a parameter pred and no parameter proj1,
• !invoke(pred, invoke(proj1, *(first1 + n)), invoke(proj2, *(first2 + n))) for the overloads with both parameters pred and proj1.
Let N be .
Returns: { first1 + n, first2 + n }, where n is the smallest integer in [0, N) such that E holds, or N if no such integer exists.
Complexity: At most N applications of the corresponding predicate and any projections.

### 25.5.11 Equal [alg.equal]

template<class InputIterator1, class InputIterator2> constexpr bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> constexpr bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, BinaryPredicate pred); template<class InputIterator1, class InputIterator2> constexpr bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> constexpr bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2> constexpr bool ranges::equal(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<InputRange R1, InputRange R2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2> constexpr bool ranges::equal(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Let:
• last2 be first2 + (last1 - first1) for the overloads with no parameter last2 or r2,
• pred be equal_­to{} for the overloads with no parameter pred,
• E be:
• pred(*i, *(first2 + (i - first1))) for the overloads with no parameter proj1,
• invoke(pred, invoke(proj1, *i), invoke(proj2, *(first2 + (i - first1)))) for the overloads with parameter proj1.
Returns: If last1 - first1 != last2 - first2, return false.
Otherwise return true if E holds for every iterator i in the range [first1, last1) Otherwise, returns false.
Complexity: If the types of first1, last1, first2, and last2:
and last1 - first1 != last2 - first2, then no applications of the corresponding predicate and each projection; otherwise,
• For the overloads with no ExecutionPolicy, at most applications of the corresponding predicate and any projections.
• For the overloads with an ExecutionPolicy, applications of the corresponding predicate.

### 25.5.12 Is permutation [alg.is.permutation]

template<class ForwardIterator1, class ForwardIterator2> constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, BinaryPredicate pred); template<class ForwardIterator1, class ForwardIterator2> constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); 
Requires: ForwardIterator1 and ForwardIterator2 shall have the same value type.
The comparison function shall be an equivalence relation.
Remarks: If last2 was not given in the argument list, it denotes first2 + (last1 - first1) below.
Returns: If last1 - first1 != last2 - first2, return false.
Otherwise return true if there exists a permutation of the elements in the range [first2, first2 + (last1 - first1)), beginning with ForwardIterator2 begin, such that equal(first1, last1, begin) returns true or equal(first1, last1, begin, pred) returns true; otherwise, returns false.
Complexity: No applications of the corresponding predicate if ForwardIterator1 and ForwardIterator2 meet the requirements of random access iterators and last1 - first1 != last2 - first2.
Otherwise, exactly last1 - first1 applications of the corresponding predicate if equal(​first1, last1, first2, last2) would return true if pred was not given in the argument list or equal(first1, last1, first2, last2, pred) would return true if pred was given in the argument list; otherwise, at worst , where N has the value last1 - first1.
template<ForwardIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2> constexpr bool ranges::is_permutation(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<ForwardRange R1, ForwardRange R2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2> constexpr bool ranges::is_permutation(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Returns: If last1 - first1 != last2 - first2, return false.
Otherwise return true if there exists a permutation of the elements in the range [first2, last2), bounded by [pfirst, plast), such that ranges::equal(first1, last1, pfirst, plast, pred, proj1, proj2) returns true; otherwise, returns false.
Complexity: No applications of the corresponding predicate and projections if:
• S1 and I1 model SizedSentinel,
• S2 and I2 model SizedSentinel, and
• last1 - first1 != last2 - first2.
Otherwise, exactly last1 - first1 applications of the corresponding predicate and projections if ranges::equal(​first1, last1, first2, last2, pred, proj1, proj2) would return true; otherwise, at worst , where N has the value last1 - first1.

### 25.5.13 Search [alg.search]

template<class ForwardIterator1, class ForwardIterator2> constexpr ForwardIterator1 search(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator1 search(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> constexpr ForwardIterator1 search(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 search(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); 
Returns: The first iterator i in the range [first1, last1 - (last2-first2)) such that for every non-negative integer n less than last2 - first2 the following corresponding conditions hold: *(i + n) == *(first2 + n), pred(*(i + n), *(first2 + n)) != false.
Returns first1 if [first2, last2) is empty, otherwise returns last1 if no such iterator is found.
Complexity: At most (last1 - first1) * (last2 - first2) applications of the corresponding predicate.
template<ForwardIterator I1, Sentinel<I1> S1, ForwardIterator I2, Sentinel<I2> S2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2> constexpr subrange<I1> ranges::search(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<ForwardRange R1, ForwardRange R2, class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity> requires IndirectlyComparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2> constexpr safe_subrange_t<R1> ranges::search(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Returns:
• {i, i + (last2 - first2)}, where i is the first iterator in the range [first1, last1 - (last2 - first2)) such that for every non-negative integer n less than last2 - first2 the condition
bool(invoke(pred, invoke(proj1, *(i + n)), invoke(proj2, *(first2 + n))))

is true:
• Returns {last1, last1} if no such iterator exists.
Complexity: At most (last1 - first1) * (last2 - first2) applications of the corresponding predicate and projections.
template<class ForwardIterator, class Size, class T> constexpr ForwardIterator search_n(ForwardIterator first, ForwardIterator last, Size count, const T& value); template<class ExecutionPolicy, class ForwardIterator, class Size, class T> ForwardIterator search_n(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Size count, const T& value); template<class ForwardIterator, class Size, class T, class BinaryPredicate> constexpr ForwardIterator search_n(ForwardIterator first, ForwardIterator last, Size count, const T& value, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator, class Size, class T, class BinaryPredicate> ForwardIterator search_n(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Size count, const T& value, BinaryPredicate pred); 
Requires: The type Size shall be convertible to integral type ([conv.integral], [class.conv]).
Returns: The first iterator i in the range [first, last-count) such that for every non-negative integer n less than count the following corresponding conditions hold: *(i + n) == value, pred(*(i + n),value) != false.
Returns last if no such iterator is found.
Complexity: At most last - first applications of the corresponding predicate.
template<ForwardIterator I, Sentinel<I> S, class T, class Pred = ranges::equal_to, class Proj = identity> requires IndirectlyComparable<I, const T*, Pred, Proj> constexpr subrange<I> ranges::search_n(I first, S last, iter_difference_t<I> count, const T& value, Pred pred = {}, Proj proj = {}); template<ForwardRange R, class T, class Pred = ranges::equal_to, class Proj = identity> requires IndirectlyComparable<iterator_t<R>, const T*, Pred, Proj> constexpr safe_subrange_t<R> ranges::search_n(R&& r, iter_difference_t<iterator_t<R>> count, const T& value, Pred pred = {}, Proj proj = {}); 
Returns: {i, i + count} where i is the first iterator in the range [first, last - count) such that for every non-negative integer n less than count, the following condition holds: invoke(pred, invoke(proj, *(i + n)), value).
Returns {last, last} if no such iterator is found.
Complexity: At most last - first applications of the corresponding predicate and projection.
template<class ForwardIterator, class Searcher> constexpr ForwardIterator search(ForwardIterator first, ForwardIterator last, const Searcher& searcher); 
Effects: Equivalent to: return searcher(first, last).first;
Remarks: Searcher need not meet the Cpp17CopyConstructible requirements.

## 25.6 Mutating sequence operations [alg.modifying.operations]

### 25.6.1 Copy [alg.copy]

template<class InputIterator, class OutputIterator> constexpr OutputIterator copy(InputIterator first, InputIterator last, OutputIterator result); template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O> requires IndirectlyCopyable<I, O> constexpr ranges::copy_result<I, O> ranges::copy(I first, S last, O result); template<InputRange R, WeaklyIncrementable O> requires IndirectlyCopyable<iterator_t<R>, O> constexpr ranges::copy_result<safe_iterator_t<R>, O> ranges::copy(R&& r, O result); 
Let N be last - first.
Requires: result shall not be in the range [first, last).
Effects: Copies elements in the range [first, last) into the range [result, result + N) starting from first and proceeding to last.
For each non-negative integer , performs *(result + n) = *(first + n).
Returns:
• result + N for the overload in namespace std, or
• {last, result + N} for the overloads in namespace ranges.
Complexity: Exactly N assignments.
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator2 copy(ExecutionPolicy&& policy, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result); 
Requires: The ranges [first, last) and [result, result + (last - first)) shall not overlap.
Effects: Copies elements in the range [first, last) into the range [result, result + (last - first)).
For each non-negative integer n < (last - first), performs *(result + n) = *(first + n).
Returns: result + (last - first).
Complexity: Exactly last - first assignments.
template<class InputIterator, class Size, class OutputIterator> constexpr OutputIterator copy_n(InputIterator first, Size n, OutputIterator result); template<class ExecutionPolicy, class ForwardIterator1, class Size, class ForwardIterator2> ForwardIterator2 copy_n(ExecutionPolicy&& exec, ForwardIterator1 first, Size n, ForwardIterator2 result); template<InputIterator I, WeaklyIncrementable O> requires IndirectlyCopyable<I, O> constexpr ranges::copy_n_result<I, O> ranges::copy_n(I first, iter_difference_t<I> n, O result); 
Let M be .
Effects: For each non-negative integer , performs *(result + i) = *(first + i).
Returns:
• result + M for the overloads in namespace std, or
• {first + M, result + M} for the overload in namespace ranges.
Complexity: Exactly M assignments.
template<class InputIterator, class OutputIterator, class Predicate> constexpr OutputIterator copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class Predicate> ForwardIterator2 copy_if(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, Predicate pred); template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> requires IndirectlyCopyable<I, O> constexpr ranges::copy_if_result<I, O> ranges::copy_if(I first, S last, O result, Pred pred, Proj proj = {}); template<InputRange R, WeaklyIncrementable O, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> requires IndirectlyCopyable<iterator_t<R>, O> constexpr ranges::copy_if_result<safe_iterator_t<R>, O> ranges::copy_if(R&& r, O result, Pred pred, Proj proj = {}); 
Let E be:
• bool(pred(*i)) for the overloads in namespace std, or
• bool(invoke(pred, invoke(proj, *i))) for the overloads in namespace ranges.
and N be the number of iterators i in the range [first, last) for which the condition E holds.
Requires: The ranges [first, last) and [result, result + (last - first)) shall not overlap.
[Note
:
For the overload with an ExecutionPolicy, there may be a performance cost if iterator_­traits<ForwardIterator1>::value_­type is not Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible).
end note
]
Effects: Copies all of the elements referred to by the iterator i in the range [first, last) for which E is true.
Returns:
• result + N for the overloads in namespace std, or
• {last, result + N} for the overloads in namespace ranges.
Complexity: Exactly last - first applications of the corresponding predicate and any projection.
Remarks: Stable ([algorithm.stable]).
template<class BidirectionalIterator1, class BidirectionalIterator2> constexpr BidirectionalIterator2 copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last, BidirectionalIterator2 result); template<BidirectionalIterator I1, Sentinel<I1> S1, BidirectionalIterator I2> requires IndirectlyCopyable<I1, I2> constexpr ranges::copy_backward_result<I1, I2> ranges::copy_backward(I1 first, S1 last, I2 result); template<BidirectionalRange R, BidirectionalIterator I> requires IndirectlyCopyable<iterator_t<R>, I> constexpr ranges::copy_backward_result<safe_iterator_t<R>, I> ranges::copy_backward(R&& r, I result); 
Let N be last - first.
Requires: result shall not be in the range (first, last].
Effects: Copies elements in the range [first, last) into the range [result - N, result) starting from last - 1 and proceeding to first.235
For each positive integer , performs *(result - n) = *(last - n).
Returns:
• result - N for the overload in namespace std, or
• {last, result - N} for the overloads in namespace ranges.
Complexity: Exactly N assignments.
copy_­backward should be used instead of copy when last is in the range [result - N, result).

### 25.6.2 Move [alg.move]

template<class InputIterator, class OutputIterator> constexpr OutputIterator move(InputIterator first, InputIterator last, OutputIterator result); template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O> requires IndirectlyMovable<I, O> constexpr ranges::move_result<I, O> ranges::move(I first, S last, O result); template<InputRange R, WeaklyIncrementable O> requires IndirectlyMovable<iterator_t<R>, O> constexpr ranges::move_result<safe_iterator_t<R>, O> ranges::move(R&& r, O result); 
Let E be
• std::move(*(first + n)) for the overload in namespace std, or
• ranges::iter_­move(first + n) for the overloads in namespace ranges.
Let N be last - first.
Requires: result shall not be in the range [first, last).
Effects: Moves elements in the range [first, last) into the range [result, result + N) starting from first and proceeding to last.
For each non-negative integer , performs *(result + n) = E.
Returns:
• result + N for the overload in namespace std, or
• {last, result + N} for the overloads in namespace ranges.
Complexity: Exactly N assignments.
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator2 move(ExecutionPolicy&& policy, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result); 
Let N be last - first.
Requires: The ranges [first, last) and [result, result + N) shall not overlap.
Effects: Moves elements in the range [first, last) into the range [result, result + N).
For each non-negative integer , performs *(result + n) = std::​move(*(first + n)).
Returns: result + N.
Complexity: Exactly N assignments.
template<class BidirectionalIterator1, class BidirectionalIterator2> constexpr BidirectionalIterator2 move_backward(BidirectionalIterator1 first, BidirectionalIterator1 last, BidirectionalIterator2 result); template<BidirectionalIterator I1, Sentinel<I1> S1, BidirectionalIterator I2> requires IndirectlyMovable<I1, I2> constexpr ranges::move_backward_result<I1, I2> ranges::move_backward(I1 first, S1 last, I2 result); template<BidirectionalRange R, BidirectionalIterator I> requires IndirectlyMovable<iterator_t<R>, I> constexpr ranges::move_backward_result<safe_iterator_t<R>, I> ranges::move_backward(R&& r, I result); 
Let E be
• std::move(*(last - n)) for the overload in namespace std, or
• ranges::iter_­move(last - n) for the overloads in namespace ranges.
Let N be last - first.
Requires: result shall not be in the range (first, last].
Effects: Moves elements in the range [first, last) into the range [result - N, result) starting from last - 1 and proceeding to first.236
For each positive integer , performs *(result - n) = E.
Returns:
• result - N for the overload in namespace std, or
• {last, result - N} for the overloads in namespace ranges.
Complexity: Exactly N assignments.
move_­backward should be used instead of move when last is in the range [result - N, result).

### 25.6.3 Swap [alg.swap]

template<class ForwardIterator1, class ForwardIterator2> constexpr ForwardIterator2 swap_ranges(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator2 swap_ranges(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2> requires IndirectlySwappable<I1, I2> constexpr ranges::swap_ranges_result<I1, I2> ranges::swap_ranges(I1 first1, S1 last1, I2 first2, S2 last2); template<InputRange R1, InputRange R2> requires IndirectlySwappable<iterator_t<R1>, iterator_t<R2>> constexpr ranges::swap_ranges_result<safe_iterator_t<R1>, safe_iterator_t<R2>> ranges::swap_ranges(R1&& r1, R2&& r2); 
Let:
• last2 be first2 + (last1 - first1) for the overloads with no parameter named last2, and
• M be .
Requires: The two ranges [first1, last1) and [first2, last2) shall not overlap.
For the overloads in namespace std, *(first1 + n) shall be swappable with ([swappable.requirements]) *(first2 + n).
Effects: For each non-negative integer performs:
• swap(*(first1 + n), *(first2 + n)) for the overloads in namespace std, or
• ranges::iter_­swap(first1 + n, first2 + n) for the overloads in namespace ranges.
Returns:
• last2 for the overloads in namespace std, or
• {first1 + M, first2 + M} for the overloads in namespace ranges.
Complexity: Exactly M swaps.
template<class ForwardIterator1, class ForwardIterator2> constexpr void iter_swap(ForwardIterator1 a, ForwardIterator2 b); 
Requires: a and b shall be dereferenceable.
*a shall be swappable with ([swappable.requirements]) *b.
Effects: As if by swap(*a, *b).

### 25.6.4 Transform [alg.transform]

template<class InputIterator, class OutputIterator, class UnaryOperation> constexpr OutputIterator transform(InputIterator first1, InputIterator last1, OutputIterator result, UnaryOperation op); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class UnaryOperation> ForwardIterator2 transform(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 result, UnaryOperation op); template<class InputIterator1, class InputIterator2, class OutputIterator, class BinaryOperation> constexpr OutputIterator transform(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, OutputIterator result, BinaryOperation binary_op); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class ForwardIterator, class BinaryOperation> ForwardIterator transform(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator result, BinaryOperation binary_op); template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, CopyConstructible F, class Proj = identity> requires Writable<O, indirect_result_t<F&, projected<I, Proj>>> constexpr ranges::unary_transform_result<I, O> ranges::transform(I first1, S last1, O result, F op, Proj proj = {}); template<InputRange R, WeaklyIncrementable O, CopyConstructible F, class Proj = identity> requires Writable<O, indirect_result_t<F&, projected<iterator_t<R>, Proj>>> constexpr ranges::unary_transform_result<safe_iterator_t<R>, O> ranges::transform(R&& r, O result, F op, Proj proj = {}); template<InputIterator I1, Sentinel<I1> S1, InputIterator I2, Sentinel<I2> S2, WeaklyIncrementable O, CopyConstructible F, class Proj1 = identity, class Proj2 = identity> requires Writable<O, indirect_result_t<F&, projected<I1, Proj1>, projected<I2, Proj2>>> constexpr ranges::binary_transform_result<I1, I2, O> ranges::transform(I1 first1, S1 last1, I2 first2, S2 last2, O result, F binary_op, Proj1 proj1 = {}, Proj2 proj2 = {}); template<InputRange R1, InputRange R2, WeaklyIncrementable O, CopyConstructible F, class Proj1 = identity, class Proj2 = identity> requires Writable<O, indirect_result_t<F&, projected<iterator_t<R1>, Proj1>, projected<iterator_t<R2>, Proj2>>> constexpr ranges::binary_transform_result<safe_iterator_t<R1>, safe_iterator_t<R2>, O> ranges::transform(R1&& r1, R2&& r2, O result, F binary_op, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Let:
• last2 be first2 + (last1 - first1) for the overloads with parameter first2 but no parameter last2,
• N be last1 - first1 for unary transforms, or for binary transforms, and
• E be
• op(*(first1 + (i - result))) for unary transforms defined in namespace std,
• binary_­op(*(first1 + (i - result)), *(first2 + (i - result))) for binary transforms defined in namespace std,
• invoke(op, invoke(proj, *(first1 + (i - result)))) for unary transforms defined in namespace ranges, or
• invoke(binary_­op, invoke(proj1, *(first1 + (i - result))), invoke(proj2,
*(first2 + (i - result))))
for binary transforms defined in namespace ranges.
Requires: op and binary_­op shall not invalidate iterators or subranges, nor modify elements in the ranges
Effects: Assigns through every iterator i in the range [result, result + N) a new corresponding value equal to E.
Returns:
• result + N for the overloads defined in namespace std,
• {first1 + N, result + N} for unary transforms defined in namespace ranges, or
• {first1 + N, first2 + N, result + N} for binary transforms defined in namespace ranges.
Complexity: Exactly N applications of op or binary_­op, and any projections.
This requirement also applies to the overload with an ExecutionPolicy.
Remarks: result may be equal to first1 or first2.
The use of fully closed ranges is intentional.

### 25.6.5 Replace [alg.replace]

template<class ForwardIterator, class T> constexpr void replace(ForwardIterator first, ForwardIterator last, const T& old_value, const T& new_value); template<class ExecutionPolicy, class ForwardIterator, class T> void replace(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& old_value, const T& new_value); template<class ForwardIterator, class Predicate, class T> constexpr void replace_if(ForwardIterator first, ForwardIterator last, Predicate pred, const T& new_value); template<class ExecutionPolicy, class ForwardIterator, class Predicate, class T> void replace_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred, const T& new_value); template<InputIterator I, Sentinel<I> S, class T1, class T2, class Proj = identity> requires Writable<I, const T2&> && IndirectRelation<ranges::equal_to, projected<I, Proj>, const T1*> constexpr I ranges::replace(I first, S last, const T1& old_value, const T2& new_value, Proj proj = {}); template<InputRange R, class T1, class T2, class Proj = identity> requires Writable<iterator_t<R>, const T2&> && IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T1*> constexpr safe_iterator_t<R> ranges::replace(R&& r, const T1& old_value, const T2& new_value, Proj proj = {}); template<InputIterator I, Sentinel<I> S, class T, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> requires Writable<I, const T&> constexpr I ranges::replace_if(I first, S last, Pred pred, const T& new_value, Proj proj = {}); template<InputRange R, class T, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> requires Writable<iterator_t<R>, const T&> constexpr safe_iterator_t<R> ranges::replace_if(R&& r, Pred pred, const T& new_value, Proj proj = {}); 
Let E be
• bool(*i == old_­value) for replace,
• bool(pred(*i)) for replace_­if,
• bool(invoke(proj, *i) == old_­value) for ranges::replace, or
• bool(invoke(pred, invoke(proj, *i))) for ranges::replace_­if.
Requires: The expression *first = new_­value shall be valid.
Effects: Substitutes elements referred by the iterator i in the range [first, last) with new_­value, when E is true.
Returns: last for the overloads in namespace ranges.
Complexity: Exactly last - first applications of the corresponding predicate and any projection.
template<class InputIterator, class OutputIterator, class T> constexpr OutputIterator replace_copy(InputIterator first, InputIterator last, OutputIterator result, const T& old_value, const T& new_value); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class T> ForwardIterator2 replace_copy(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, const T& old_value, const T& new_value); template<class InputIterator, class OutputIterator, class Predicate, class T> constexpr OutputIterator replace_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred, const T& new_value); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class Predicate, class T> ForwardIterator2 replace_copy_if(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, Predicate pred, const T& new_value); template<InputIterator I, Sentinel<I> S, class T1, class T2, OutputIterator<const T2&> O, class Proj = identity> requires IndirectlyCopyable<I, O> && IndirectRelation<ranges::equal_to, projected<I, Proj>, const T1*> constexpr ranges::replace_copy_result<I, O> ranges::replace_copy(I first, S last, O result, const T1& old_value, const T2& new_value, Proj proj = {}); template<InputRange R, class T1, class T2, OutputIterator<const T2&> O, class Proj = identity> requires IndirectlyCopyable<iterator_t<R>, O> && IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T1*> constexpr ranges::replace_copy_result<safe_iterator_t<R>, O> ranges::replace_copy(R&& r, O result, const T1& old_value, const T2& new_value, Proj proj = {}); template<InputIterator I, Sentinel<I> S, class T, OutputIterator<const T&> O, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> requires IndirectlyCopyable<I, O> constexpr ranges::replace_copy_if_result<I, O> ranges::replace_copy_if(I first, S last, O result, Pred pred, const T& new_value, Proj proj = {}); template<InputRange R, class T, OutputIterator<const T&> O, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> requires IndirectlyCopyable<iterator_t<R>, O> constexpr ranges::replace_copy_if_result<safe_iterator_t<R>, O> ranges::replace_copy_if(R&& r, O result, Pred pred, const T& new_value, Proj proj = {}); 
Let E be
• bool(*(first + (i - result)) == old_­value) for replace_­copy,
• bool(pred(*(first + (i - result)))) for replace_­copy_­if,
• bool(invoke(proj, *(first + (i - result))) == old_­value) for ranges::replace_­copy,
• bool(invoke(pred, invoke(proj, *(first + (i - result))))) for ranges::replace_­copy_­if.
Requires: The results of the expressions *first and new_­value shall be writable ([iterator.requirements.general]) to the result output iterator.
The ranges [first, last) and [result, result + (last - first)) shall not overlap.
Effects: Assigns to every iterator i in the range [result, result + (last - first)) either new_­value or *(first + (i - result)) depending on whether E holds.
Returns:
• result + (last - first) for the overloads in namespace std, or
• {last, result + (last - first)} for the overloads in namespace ranges.
Complexity: Exactly last - first applications of the corresponding predicate and any projection.

### 25.6.6 Fill [alg.fill]

template<class ForwardIterator, class T> constexpr void fill(ForwardIterator first, ForwardIterator last, const T& value); template<class ExecutionPolicy, class ForwardIterator, class T> void fill(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& value); template<class OutputIterator, class Size, class T> constexpr OutputIterator fill_n(OutputIterator first, Size n, const T& value); template<class ExecutionPolicy, class ForwardIterator, class Size, class T> ForwardIterator fill_n(ExecutionPolicy&& exec, ForwardIterator first, Size n, const T& value); template<class T, OutputIterator<const T&> O, Sentinel<O> S> constexpr O ranges::fill(O first, S last, const T& value); template<class T, OutputRange<const T&> R> constexpr safe_iterator_t<R> ranges::fill(R&& r, const T& value); template<class T, OutputIterator<const T&> O> constexpr O ranges::fill_n(O first, iter_difference_t<O> n, const T& value); 
Let N be for the fill_­n algorithms, and last - first for the fill algorithms.
Requires: The expression value shall be writable ([iterator.requirements.general]) to the output iterator.
The type Size shall be convertible to an integral type ([conv.integral], [class.conv]).
Effects: Assigns value through all the iterators in the range [first, first + N).
Returns: first + N.
Complexity: Exactly N assignments.

### 25.6.7 Generate [alg.generate]

template<class ForwardIterator, class Generator> constexpr void generate(ForwardIterator first, ForwardIterator last, Generator gen); template<class ExecutionPolicy, class ForwardIterator, class Generator> void generate(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Generator gen); template<class OutputIterator, class Size, class Generator> constexpr OutputIterator generate_n(OutputIterator first, Size n, Generator gen); template<class ExecutionPolicy, class ForwardIterator, class Size, class Generator> ForwardIterator generate_n(ExecutionPolicy&& exec, ForwardIterator first, Size n, Generator gen); template<Iterator O, Sentinel<O> S, CopyConstructible F> requires Invocable<F&> && Writable<O, invoke_result_t<F&>> constexpr O ranges::generate(O first, S last, F gen); template<class R, CopyConstructible F> requires Invocable<F&> && OutputRange<R, invoke_result_t<F&>> constexpr safe_iterator_t<R> ranges::generate(R&& r, F gen); template<Iterator O, CopyConstructible F> requires Invocable<F&> && Writable<O, invoke_result_t<F&>> constexpr O ranges::generate_n(O first, iter_difference_t<O> n, F gen); 
Let N be for the generate_­n algorithms, and last - first for the generate algorithms.
Requires: Size shall be convertible to an integral type ([conv.integral], [class.conv]).
Effects: Assigns the result of successive evaluations of gen() through each iterator in the range [first, first + N).
Returns: first + N.
Complexity: Exactly N evaluations of gen() and assignments.

### 25.6.8 Remove [alg.remove]

template<class ForwardIterator, class T> constexpr ForwardIterator remove(ForwardIterator first, ForwardIterator last, const T& value); template<class ExecutionPolicy, class ForwardIterator, class T> ForwardIterator remove(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& value); template<class ForwardIterator, class Predicate> constexpr ForwardIterator remove_if(ForwardIterator first, ForwardIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> ForwardIterator remove_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<Permutable I, Sentinel<I> S, class T, class Proj = identity> requires IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*> constexpr I ranges::remove(I first, S last, const T& value, Proj proj = {}); template<ForwardRange R, class T, class Proj = identity> requires Permutable<iterator_t<R>> && IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> constexpr safe_iterator_t<R> ranges::remove(R&& r, const T& value, Proj proj = {}); template<Permutable I, Sentinel<I> S, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> constexpr I ranges::remove_if(I first, S last, Pred pred, Proj proj = {}); template<ForwardRange R, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> requires Permutable<iterator_t<R>> constexpr safe_iterator_t<R> ranges::remove_if(R&& r, Pred pred, Proj proj = {}); 
Let E be
• bool(*i == value) for remove,
• bool(pred(*i)) for remove_­if,
• bool(invoke(proj, *i) == value) for ranges::remove, or
• bool(invoke(pred, invoke(proj, *i))) for ranges::remove_­if.
Requires: For the algorithms in namespace std, the type of *first shall meet the Cpp17MoveAssignable requirements ([tab:moveassignable]Table *tab:moveassignable).
Effects: Eliminates all the elements referred to by iterator i in the range [first, last) for which E holds.
Returns: The end of the resulting range.
Remarks: Stable ([algorithm.stable]).
Complexity: Exactly last - first applications of the corresponding predicate and any projection.
[Note
:
Each element in the range [ret, last), where ret is the returned value, has a valid but unspecified state, because the algorithms can eliminate elements by moving from elements that were originally in that range.
end note
]
template<class InputIterator, class OutputIterator, class T> constexpr OutputIterator remove_copy(InputIterator first, InputIterator last, OutputIterator result, const T& value); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class T> ForwardIterator2 remove_copy(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, const T& value); template<class InputIterator, class OutputIterator, class Predicate> constexpr OutputIterator remove_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class Predicate> ForwardIterator2 remove_copy_if(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, Predicate pred); template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, class T, class Proj = identity> requires IndirectlyCopyable<I, O> && IndirectRelation<ranges::equal_to, projected<I, Proj>, const T*> constexpr ranges::remove_copy_result<I, O> ranges::remove_copy(I first, S last, O result, const T& value, Proj proj = {}); template<InputRange R, WeaklyIncrementable O, class T, class Proj = identity> requires IndirectlyCopyable<iterator_t<R>, O> && IndirectRelation<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> constexpr ranges::remove_copy_result<safe_iterator_t<R>, O> ranges::remove_copy(R&& r, O result, const T& value, Proj proj = {}); template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, class Proj = identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> requires IndirectlyCopyable<I, O> constexpr ranges::remove_copy_if_result<I, O> ranges::remove_copy_if(I first, S last, O result, Pred pred, Proj proj = {}); template<InputRange R, WeaklyIncrementable O, class Proj = identity, IndirectUnaryPredicate<projected<iterator_t<R>, Proj>> Pred> requires IndirectlyCopyable<iterator_t<R>, O> constexpr ranges::remove_copy_if_result<safe_iterator_t<R>, O> ranges::remove_copy_if(R&& r, O result, Pred pred, Proj proj = {}); 
Let E be
• bool(*i == value) for remove_­copy,
• bool(pred(*i)) for remove_­copy_­if,
• bool(invoke(proj, *i) == value) for ranges::remove_­copy, or
• bool(invoke(pred, invoke(proj, *i))) for ranges::remove_­copy_­if.
Let N be the number of elements in [first, last) for which E is false.
Requires: The ranges [first, last) and [result, result + (last - first)) shall not overlap.
The expression *result = *first shall be valid.
[Note
:
For the overloads with an ExecutionPolicy, there may be a performance cost if iterator_­traits<ForwardIterator1>::value_­type does not meet the Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible) requirements.
end note
]
Effects: Copies all the elements referred to by the iterator i in the range [first, last) for which E is false.
Returns:
• result + N, for the algorithms in namespace std, or
• {last, result + N}, for the algorithms in namespace ranges.
Complexity: Exactly last - first applications of the corresponding predicate and any projection.
Remarks: Stable ([algorithm.stable]).

### 25.6.9 Unique [alg.unique]

template<class ForwardIterator> constexpr ForwardIterator unique(ForwardIterator first, ForwardIterator last); template<class ExecutionPolicy, class ForwardIterator> ForwardIterator unique(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last); template<class ForwardIterator, class BinaryPredicate> constexpr ForwardIterator unique(ForwardIterator first, ForwardIterator last, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator, class BinaryPredicate> ForwardIterator unique(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, BinaryPredicate pred); template<Permutable I, Sentinel<I> S, class Proj = identity, IndirectRelation<projected<I, Proj>> C = ranges::equal_to> constexpr I ranges::unique(I first, S last, C comp = {}, Proj proj = {}); template<ForwardRange R, class Proj = identity, IndirectRelation<projected<iterator_t<R>, Proj>> C = ranges::equal_to> requires Permutable<iterator_t<R>> constexpr safe_iterator_t<R> ranges::unique(R&& r, C comp = {}, Proj proj = {}); 
Let pred be equal_­to{} for the overloads with no parameter pred, and let E be
• bool(pred(*(i - 1), *i)) for the overloads in namespace std, or
• bool(invoke(comp, invoke(proj, *(i - 1)), invoke(proj, *i))) for the overloads in namespace ranges.
Requires: For the overloads in namepace std, pred shall be an equivalence relation and the type of *first shall meet the Cpp17MoveAssignable requirements ([tab:moveassignable]Table *tab:moveassignable).
Effects: For a nonempty range, eliminates all but the first element from every consecutive group of equivalent elements referred to by the iterator i in the range [first + 1, last) for which E is true.
Returns: The end of the resulting range.
Complexity: For nonempty ranges, exactly (last - first) - 1 applications of the corresponding predicate and no more than twice as many applications of any projection.
template<class InputIterator, class OutputIterator> constexpr OutputIterator unique_copy(InputIterator first, InputIterator last, OutputIterator result); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator2 unique_copy(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result); template<class InputIterator, class OutputIterator, class BinaryPredicate> constexpr OutputIterator unique_copy(InputIterator first, InputIterator last, OutputIterator result, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator2 unique_copy(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, BinaryPredicate pred); template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, class Proj = identity, IndirectRelation<projected<I, Proj>> C = ranges::equal_to> requires IndirectlyCopyable<I, O> && (ForwardIterator<I> || (InputIterator<O> && Same<iter_value_t<I>, iter_value_t<O>>) || IndirectlyCopyableStorable<I, O>) constexpr ranges::unique_copy_result<I, O> ranges::unique_copy(I first, S last, O result, C comp = {}, Proj proj = {}); template<InputRange R, WeaklyIncrementable O, class Proj = identity, IndirectRelation<projected<iterator_t<R>, Proj>> C = ranges::equal_to> requires IndirectlyCopyable<iterator_t<R>, O> && (ForwardIterator<iterator_t<R>> || (InputIterator<O> && Same<iter_value_t<iterator_t<R>>, iter_value_t<O>>) || IndirectlyCopyableStorable<iterator_t<R>, O>) constexpr ranges::unique_copy_result<safe_iterator_t<R>, O> ranges::unique_copy(R&& r, O result, C comp = {}, Proj proj = {}); 
Let pred be equal_­to{} for the overloads in namespace std with no parameter pred, and let E be
• bool(pred(*i, *(i - 1))) for the overloads in namespace std, or
• bool(invoke(comp, invoke(proj, *i), invoke(proj, *(i - 1)))) for the overloads in namespace ranges.
Requires:
• The ranges [first, last) and [result, result+(last-first)) shall not overlap.
• For the overloads in namespace std:
• The comparison function shall be an equivalence relation.
• The expression *result = *first shall be valid.
• For the overloads with no ExecutionPolicy, let T be the value type of InputIterator.
If InputIterator meets the Cpp17ForwardIterator requirements, then there are no additional requirements for T.
Otherwise, if OutputIterator meets the Cpp17ForwardIterator requirements and its value type is the same as T, then T shall meet the Cpp17CopyAssignable ([tab:copyassignable]Table *tab:copyassignable) requirements.
Otherwise, T shall meet both the Cpp17CopyConstructible ([tab:copyconstructible]Table *tab:copyconstructible) and Cpp17CopyAssignable requirements.
[Note
:
For the overloads with an ExecutionPolicy, there may be a performance cost if the value type of ForwardIterator1 does not meet both the Cpp17CopyConstructible and Cpp17CopyAssignable requirements.
end note
]
Effects: Copies only the first element from every consecutive group of equal elements referred to by the iterator i in the range [first, last) for which E holds.
Returns:
• result + N for the overloads in namespace std, or
• {last, result + N} for the overloads in namespace ranges
Complexity: Exactly last - first - 1 applications of the corresponding predicate and no more than twice as many applications of any projection.

### 25.6.10 Reverse [alg.reverse]

template<class BidirectionalIterator> constexpr void reverse(BidirectionalIterator first, BidirectionalIterator last); template<class ExecutionPolicy, class BidirectionalIterator> void reverse(ExecutionPolicy&& exec, BidirectionalIterator first, BidirectionalIterator last); template<BidirectionalIterator I, Sentinel<I> S> requires Permutable<I> constexpr I ranges::reverse(I first, S last); template<BidirectionalRange R> requires Permutable<iterator_t<R>> constexpr safe_iterator_t<R> ranges::reverse(R&& r); 
Requires: For the overloads in namespace std, BidirectionalIterator shall meet the Cpp17ValueSwappable requirements ([swappable.requirements]).
Effects: For each non-negative integer i < (last - first) / 2, applies std::iter_­swap, or ranges::​iter_­swap for the overloads in namespace ranges, to all pairs of iterators first + i, (last - i) - 1.
Returns: last for the overloads in namespace ranges.
Complexity: Exactly (last - first)/2 swaps.
template<class BidirectionalIterator, class OutputIterator> constexpr OutputIterator reverse_copy(BidirectionalIterator first, BidirectionalIterator last, OutputIterator result); template<class ExecutionPolicy, class BidirectionalIterator, class ForwardIterator> ForwardIterator reverse_copy(ExecutionPolicy&& exec, BidirectionalIterator first, BidirectionalIterator last, ForwardIterator result); template<BidirectionalIterator I, Sentinel<I> S, WeaklyIncrementable O> requires IndirectlyCopyable<I, O> constexpr ranges::reverse_copy_result<I, O> ranges::reverse_copy(I first, S last, O result); template<BidirectionalRange R, WeaklyIncrementable O> requires IndirectlyCopyable<iterator_t<R>, O> constexpr ranges::reverse_copy_result<safe_iterator_t<R>, O> ranges::reverse_copy(R&& r, O result); 
Let N be last - first.
Requires: The ranges [first, last) and [result, result + N) shall not overlap.
Effects: Copies the range [first, last) to the range [result, result + N) such that for every non-negative integer i < N the following assignment takes place: *(result + N - 1 - i) = *(first + i).
Returns:
• result + N for the overloads in namespace std, or
• {last, result + N} for the overloads in namespace ranges.
Complexity: Exactly N assignments.

### 25.6.11 Rotate [alg.rotate]

template<class ForwardIterator> constexpr ForwardIterator rotate(ForwardIterator first, ForwardIterator middle, ForwardIterator last); template<class ExecutionPolicy, class ForwardIterator> ForwardIterator rotate(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator middle, ForwardIterator last); template<Permutable I, Sentinel<I> S> constexpr subrange<I> ranges::rotate(I first, I middle, S last); 
Requires: [first, middle) and [middle, last) shall be valid ranges.
For the overloads in namespace std, ForwardIterator shall meet the Cpp17ValueSwappable requirements ([swappable.requirements]), and the type of *first shall meet the Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible) and Cpp17MoveAssignable ([tab:moveassignable]Table *tab:moveassignable) requirements.
Effects: For each non-negative integer i < (last - first), places the element from the position first + i into position first + (i + (last - middle)) % (last - first).
[Note
:
This is a left rotate.
end note
]
Returns:
• first + (last - middle) for the overloads in namespace std, or
• {first + (last - middle), last} for the overload in namespace ranges.
Complexity: At most last - first swaps.
template<ForwardRange R> requires Permutable<iterator_t<R>> constexpr safe_subrange_t<R> ranges::rotate(R&& r, iterator_t<R> middle); 
Effects: Equivalent to: return ranges::rotate(ranges::begin(r), middle, ranges::end(r));
template<class ForwardIterator, class OutputIterator> constexpr OutputIterator rotate_copy(ForwardIterator first, ForwardIterator middle, ForwardIterator last, OutputIterator result); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator2 rotate_copy(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 middle, ForwardIterator1 last, ForwardIterator2 result); template<ForwardIterator I, Sentinel<I> S, WeaklyIncrementable O> requires IndirectlyCopyable<I, O> constexpr ranges::rotate_copy_result<I, O> ranges::rotate_copy(I first, I middle, S last, O result); 
Let N be last - first.
Requires: [first, middle) and [middle, last) shall be valid ranges.
The ranges [first, last) and [result, result + N) shall not overlap.
Effects: Copies the range [first, last) to the range [result, result + N) such that for each non-negative integer the following assignment takes place: *(result + i) = *(first + (i + (middle - first)) % N).
Returns:
• result + N for the overloads in namespace std, or
• {last, result + N} for the overload in namespace ranges.
Complexity: Exactly N assignments.
template<ForwardRange R, WeaklyIncrementable O> requires IndirectlyCopyable<iterator_t<R>, O> constexpr ranges::rotate_copy_result<safe_iterator_t<R>, O> ranges::rotate_copy(R&& r, iterator_t<R> middle, O result); 
Effects: Equivalent to:
return ranges::rotate_copy(ranges::begin(r), middle, ranges::end(r), result);


### 25.6.12 Sample [alg.random.sample]

template<class PopulationIterator, class SampleIterator, class Distance, class UniformRandomBitGenerator> SampleIterator sample(PopulationIterator first, PopulationIterator last, SampleIterator out, Distance n, UniformRandomBitGenerator&& g); 
Requires:
Effects: Copies elements (the sample) from [first, last) (the population) to out such that each possible sample has equal probability of appearance.
[Note
:
Algorithms that obtain such effects include selection sampling and reservoir sampling.
end note
]
Returns: The end of the resulting sample range.
Complexity: .
Remarks:
• Stable if and only if PopulationIterator satisfies the Cpp17ForwardIterator requirements.
• To the extent that the implementation of this function makes use of random numbers, the object g shall serve as the implementation's source of randomness.

### 25.6.13 Shuffle [alg.random.shuffle]

template<class RandomAccessIterator, class UniformRandomBitGenerator> void shuffle(RandomAccessIterator first, RandomAccessIterator last, UniformRandomBitGenerator&& g); template<RandomAccessIterator I, Sentinel<I> S, class Gen> requires Permutable<I> && UniformRandomBitGenerator<remove_reference_t<Gen>> I ranges::shuffle(I first, S last, Gen&& g); template<RandomAccessRange R, class Gen> requires Permutable<iterator_t<R>> && UniformRandomBitGenerator<remove_reference_t<Gen>> safe_iterator_t<R> ranges::shuffle(R&& r, Gen&& g); 
Requires: For the overload in namespace std:
Effects: Permutes the elements in the range [first, last) such that each possible permutation of those elements has equal probability of appearance.
Returns: last for the overloads in namespace ranges.
Complexity: Exactly (last - first) - 1 swaps.
Remarks: To the extent that the implementation of this function makes use of random numbers, the object referenced by g shall serve as the implementation's source of randomness.

### 25.6.14 Shift [alg.shift]

template<class ForwardIterator> constexpr ForwardIterator shift_left(ForwardIterator first, ForwardIterator last, typename iterator_traits<ForwardIterator>::difference_type n); template<class ExecutionPolicy, class ForwardIterator> ForwardIterator shift_left(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, typename iterator_traits<ForwardIterator>::difference_type n); 
Requires: The type of *first shall satisfy the Cpp17MoveAssignable requirements.
Effects: If n <= 0 or n >= last - first, does nothing.
Otherwise, moves the element from position first + n + i into position first + i for each non-negative integer i < (last - first) - n.
In the first overload case, does so in order starting from i = 0 and proceeding to i = (last - first) - n - 1.
Returns: first + (last - first - n) if n is positive and n < last - first, otherwise first if n is positive, otherwise last.
Complexity: At most (last - first) - n assignments.
template<class ForwardIterator> constexpr ForwardIterator shift_right(ForwardIterator first, ForwardIterator last, typename iterator_traits<ForwardIterator>::difference_type n); template<class ExecutionPolicy, class ForwardIterator> ForwardIterator shift_right(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, typename iterator_traits<ForwardIterator>::difference_type n); 
Requires: The type of *first shall satisfy the Cpp17MoveAssignable requirements.
ForwardIterator shall meet the Cpp17BidirectionalIterator requirements ([bidirectional.iterators]) or the Cpp17ValueSwappable requirements.
Effects: If n <= 0 or n >= last - first, does nothing.
Otherwise, moves the element from position first + i into position first + n + i for each non-negative integer i < (last - first) - n.
In the first overload case, if ForwardIterator satisfies the Cpp17BidirectionalIterator requirements, does so in order starting from i = (last - first) - n - 1 and proceeding to i = 0.
Returns: first + n if n is positive and n < last - first, otherwise last if n is positive, otherwise first.
Complexity: At most (last - first) - n assignments or swaps.

## 25.7 Sorting and related operations [alg.sorting]

The operations in [alg.sorting] defined directly in namespace std have two versions: one that takes a function object of type Compare and one that uses an operator<.
Compare is a function object type ([function.objects]) that meets the requirements for a template parameter named BinaryPredicate ([algorithms.requirements]).
The return value of the function call operation applied to an object of type Compare, when contextually converted to bool ([conv]), yields true if the first argument of the call is less than the second, and false otherwise.
Compare comp is used throughout for algorithms assuming an ordering relation.
For all algorithms that take Compare, there is a version that uses operator< instead.
That is, comp(*i, *j) != false defaults to *i < *j != false.
For algorithms other than those described in [alg.binary.search], comp shall induce a strict weak ordering on the values.
The term strict refers to the requirement of an irreflexive relation (!comp(x, x) for all x), and the term weak to requirements that are not as strong as those for a total ordering, but stronger than those for a partial ordering.
If we define equiv(a, b) as !comp(a, b) && !comp(b, a), then the requirements are that comp and equiv both be transitive relations:
• comp(a, b) && comp(b, c) implies comp(a, c)
• equiv(a, b) && equiv(b, c) implies equiv(a, c)
[Note
:
Under these conditions, it can be shown that
• equiv is an equivalence relation,
• comp induces a well-defined relation on the equivalence classes determined by equiv, and
• the induced relation is a strict total ordering.
end note
]
A sequence is sorted with respect to a comp and proj for a comparator and projection comp and proj if for every iterator i pointing to the sequence and every non-negative integer n such that i + n is a valid iterator pointing to an element of the sequence,
bool(invoke(comp, invoke(proj, *(i + n)), invoke(proj, *i)))

is false.
A sequence [start, finish) is partitioned with respect to an expression f(e) if there exists an integer n such that for all 0 <= i < (finish - start), f(*(start + i)) is true if and only if i < n.
In the descriptions of the functions that deal with ordering relationships we frequently use a notion of equivalence to describe concepts such as stability.
The equivalence to which we refer is not necessarily an operator==, but an equivalence relation induced by the strict weak ordering.
That is, two elements a and b are considered equivalent if and only if !(a < b) && !(b < a).

### 25.7.1 Sorting [alg.sort]

#### 25.7.1.1sort[sort]

template<class RandomAccessIterator> constexpr void sort(RandomAccessIterator first, RandomAccessIterator last); template<class ExecutionPolicy, class RandomAccessIterator> void sort(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator last); template<class RandomAccessIterator, class Compare> constexpr void sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp); template<class ExecutionPolicy, class RandomAccessIterator, class Compare> void sort(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator last, Compare comp); template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less, class Proj = identity> requires Sortable<I, Comp, Proj> constexpr I ranges::sort(I first, S last, Comp comp = {}, Proj proj = {}); template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity> requires Sortable<iterator_t<R>, Comp, Proj> constexpr safe_iterator_t<R> ranges::sort(R&& r, Comp comp = {}, Proj proj = {}); 
Let comp be less{} and proj be identity{} for the overloads with no parameters by those names.
Requires: For the overloads in namespace std, RandomAccessIterator shall meet the Cpp17ValueSwappable requirements ([swappable.requirements]) and the type of *first shall meet the Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible) and Cpp17MoveAssignable ([tab:moveassignable]Table *tab:moveassignable) requirements.
Effects: Sorts the elements in the range [first, last) with respect to comp and proj.
Returns: last, for the overloads in namespace ranges.
Complexity: Let N be last - first.
comparisons and projections.

#### 25.7.1.2stable_­sort[stable.sort]

template<class RandomAccessIterator> void stable_sort(RandomAccessIterator first, RandomAccessIterator last); template<class ExecutionPolicy, class RandomAccessIterator> void stable_sort(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator last); template<class RandomAccessIterator, class Compare> void stable_sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp); template<class ExecutionPolicy, class RandomAccessIterator, class Compare> void stable_sort(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator last, Compare comp); template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less, class Proj = identity> requires Sortable<I, Comp, Proj> I ranges::stable_sort(I first, S last, Comp comp = {}, Proj proj = {}); template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity> requires Sortable<iterator_t<R>, Comp, Proj> safe_iterator_t<R> ranges::stable_sort(R&& r, Comp comp = {}, Proj proj = {}); 
Let comp be less{} and proj be identity{} for the overloads with no parameters by those names.
Requires: For the overloads in namespace std, RandomAccessIterator shall meet the Cpp17ValueSwappable requirements ([swappable.requirements]) and the type of *first shall meet the Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible) and Cpp17MoveAssignable ([tab:moveassignable]Table *tab:moveassignable) requirements.
Effects: Sorts the elements in the range [first, last) with respect to comp and proj.
Returns: last for the overloads in namespace ranges.
Complexity: Let N be last - first.
If enough extra memory is available, comparisons.
Otherwise, at most comparisons.
In either case, twice as many projections as the number of comparisons.
Remarks: Stable ([algorithm.stable]).

#### 25.7.1.3partial_­sort[partial.sort]

template<class RandomAccessIterator> constexpr void partial_sort(RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last); template<class ExecutionPolicy, class RandomAccessIterator> void partial_sort(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last); template<class RandomAccessIterator, class Compare> constexpr void partial_sort(RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last, Compare comp); template<class ExecutionPolicy, class RandomAccessIterator, class Compare> void partial_sort(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last, Compare comp); template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less, class Proj = identity> requires Sortable<I, Comp, Proj> constexpr I ranges::partial_sort(I first, I middle, S last, Comp comp = {}, Proj proj = {}); 
Let comp be less{} and proj be identity{} for the overloads with no parameters by those names.
Requires: [first, middle) and [middle, last) shall be valid ranges.
For the overloads in namespace std, RandomAccessIterator shall meet the Cpp17ValueSwappable requirements ([swappable.requirements]) and the type of *first shall meet the Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible) and Cpp17MoveAssignable ([tab:moveassignable]Table *tab:moveassignable) requirements.
Effects: Places the first middle - first elements from the range [first, last) as sorted with respect to comp and proj into the range [first, middle).
The rest of the elements in the range [middle, last) are placed in an unspecified order.
Returns: last for the overload in namespace ranges.
Complexity: Approximately (last - first) * log(middle - first) comparisons, and twice as many projections.
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity> requires Sortable<iterator_t<R>, Comp, Proj> constexpr safe_iterator_t<R> ranges::partial_sort(R&& r, iterator_t<R> middle, Comp comp = {}, Proj proj = {}); 
Effects: Equivalent to:
return ranges::partial_sort(ranges::begin(r), middle, ranges::end(r), comp, proj);


#### 25.7.1.4partial_­sort_­copy[partial.sort.copy]

template<class InputIterator, class RandomAccessIterator> constexpr RandomAccessIterator partial_sort_copy(InputIterator first, InputIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last); template<class ExecutionPolicy, class ForwardIterator, class RandomAccessIterator> RandomAccessIterator partial_sort_copy(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last); template<class InputIterator, class RandomAccessIterator, class Compare> constexpr RandomAccessIterator partial_sort_copy(InputIterator first, InputIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last, Compare comp); template<class ExecutionPolicy, class ForwardIterator, class RandomAccessIterator, class Compare> RandomAccessIterator partial_sort_copy(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last, Compare comp); template<InputIterator I1, Sentinel<I1> S1, RandomAccessIterator I2, Sentinel<I2> S2, class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity> requires IndirectlyCopyable<I1, I2> && Sortable<I2, Comp, Proj2> && IndirectStrictWeakOrder<Comp, projected<I1, Proj1>, projected<I2, Proj2>> constexpr I2 ranges::partial_sort_copy(I1 first, S1 last, I2 result_first, S2 result_last, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<InputRange R1, RandomAccessRange R2, class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity> requires IndirectlyCopyable<iterator_t<R1>, iterator_t<R2>> && Sortable<iterator_t<R2>, Comp, Proj2> && IndirectStrictWeakOrder<Comp, projected<iterator_t<R1>, Proj1>, projected<iterator_t<R2>, Proj2>> constexpr safe_iterator_t<R2> ranges::partial_sort_copy(R1&& r, R2&& result_r, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); 
Let N be .
Let comp be less{}, and proj1 and proj2 be identity{} for the overloads with no parameters by those names.
Requires: For the overloads in namespace std, RandomAccessIterator shall meet the Cpp17ValueSwappable requirements ([swappable.requirements]), the type of *result_­first shall meet the Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible) and Cpp17MoveAssignable ([tab:moveassignable]Table *tab:moveassignable) requirements, and the expression *first shall be writable ([iterator.requirements.general]) to result_­first.
Expects: For iterators a1 and b1 in [first, last), and iterators x2 and y2 in [result_­first, result_­last), after evaluating the assignment *y2 = *b1, let E be the value of
bool(invoke(comp, invoke(proj1, *a1), invoke(proj2, *y2))).

Then, after evaluating the assignment *x2 = *a1, E is equal to
bool(invoke(comp, invoke(proj2, *x2), invoke(proj2, *y2))).

[Note
:
Writing a value from the input range into the output range does not affect how it is ordered by comp and proj1 or proj2.
end note
]
Effects: Places the first N elements as sorted with respect to comp and proj2 into the range [result_­first, result_­first + N).
Returns: result_­first + N.
Complexity: Approximately (last - first) * log N comparisons, and twice as many projections.

#### 25.7.1.5is_­sorted[is.sorted]

template<class ForwardIterator> constexpr bool is_sorted(ForwardIterator first, ForwardIterator last); 
Effects: Equivalent to: return is_­sorted_­until(first, last) == last;
template<class ExecutionPolicy, class ForwardIterator> bool is_sorted(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last); 
Effects: Equivalent to:
return is_sorted_until(std::forward<ExecutionPolicy>(exec), first, last) == last;

template<class ForwardIterator, class Compare> constexpr bool is_sorted(ForwardIterator first, ForwardIterator last, Compare comp); 
Effects: Equivalent to: return is_­sorted_­until(first, last, comp) == last;
template<class ExecutionPolicy, class ForwardIterator, class Compare> bool is_sorted(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Compare comp); 
Effects: Equivalent to:
is_sorted_until(std::forward<ExecutionPolicy>(exec), first, last, comp) == last

template<ForwardIterator I, Sentinel<I> S, class Proj = identity, IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less> constexpr bool ranges::is_sorted(I first, S last, Comp comp = {}, Proj proj = {}); template<ForwardRange R, class Proj = identity, IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less> constexpr bool ranges::is_sorted(R&& r, Comp comp = {}, Proj proj = {}); 
Effects: Equivalent to: return ranges::is_­sorted_­until(first, last, comp, proj) == last;
template<class ForwardIterator> constexpr ForwardIterator is_sorted_until(ForwardIterator first, ForwardIterator last); template<class ExecutionPolicy, class ForwardIterator> ForwardIterator is_sorted_until(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last); template<class ForwardIterator, class Compare> constexpr ForwardIterator is_sorted_until(ForwardIterator first, ForwardIterator last, Compare comp); template<class ExecutionPolicy, class ForwardIterator, class Compare> ForwardIterator is_sorted_until(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Compare comp); template<ForwardIterator I, Sentinel<I> S, class Proj = identity, IndirectStrictWeakOrder<projected<I, Proj>> Comp = ranges::less> constexpr I ranges::is_sorted_until(I first, S last, Comp comp = {}, Proj proj = {}); template<ForwardRange R, class Proj = identity, IndirectStrictWeakOrder<projected<iterator_t<R>, Proj>> Comp = ranges::less> constexpr safe_iterator_t<R> ranges::is_sorted_until(R&& r, Comp comp = {}, Proj proj = {}); 
Let comp be less{} and proj be identity{} for the overloads with no parameters by those names.
Returns: The last iterator i in [first, last] for which the range [first, i) is sorted with respect to comp and proj.
Complexity: Linear.

### 25.7.2 Nth element [alg.nth.element]

template<class RandomAccessIterator> constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last); template<class ExecutionPolicy, class RandomAccessIterator> void nth_element(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last); template<class RandomAccessIterator, class Compare> constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last, Compare comp); template<class ExecutionPolicy, class RandomAccessIterator, class Compare> void nth_element(ExecutionPolicy&& exec, RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last, Compare comp); template<RandomAccessIterator I, Sentinel<I> S, class Comp = ranges::less, class Proj = identity> requires Sortable<I, Comp, Proj> constexpr I ranges::nth_element(I first, I nth, S last, Comp comp = {}, Proj proj = {}); 
Let comp be less{} and proj be identity{} for the overloads with no parameters by those names.
Requires: [first, nth) and [nth, last) shall be valid ranges.
For the overloads in namespace std, RandomAccessIterator shall meet the Cpp17ValueSwappable requirements ([swappable.requirements]), and the type of *first shall meet the Cpp17MoveConstructible ([tab:moveconstructible]Table *tab:moveconstructible) and Cpp17MoveAssignable ([tab:moveassignable]Table *tab:moveassignable) requirements.
Effects: After nth_­element the element in the position pointed to by nth is the element that would be in that position if the whole range were sorted with respect to comp and proj, unless nth == last.
Also for every iterator i in the range [first, nth) and every iterator j in the range [nth, last) it holds that: bool(invoke(comp, invoke(proj, *j), invoke(proj, *i))) is false.
Returns: last for the overload in namespace ranges.
Complexity: For the overloads with no ExecutionPolicy, linear on average.
For the overloads with an ExecutionPolicy, applications of the predicate, and swaps, where .
template<RandomAccessRange R, class Comp = ranges::less, class Proj = identity> requires Sortable<iterator_t<R>, Comp, Proj> constexpr safe_iterator_t<R> ranges::nth_element(R&& r, iterator_t<R> nth, Comp comp = {}, Proj proj = {}); 
Effects: Equivalent to:
return ranges::nth_element(ranges::begin(r), nth, ranges::end(r), comp, proj);


### 25.7.3 Binary search [alg.binary.search]

All of the algorithms in this subclause are versions of binary search and assume that the sequence being searched is partitioned with respect to an expression formed by binding the search key to an argument of the comparison function.
They work on non-random access iterators minimizing the number of comparisons, which will be logarithmic for all types of iterators.
They are especially appropriate for random access iterators, because these algorithms do a logarithmic number of steps through the data structure.
For non-random access iterators they execute a linear number of steps.

#### 25.7.3.1lower_­bound[lower.bound]

template<class ForwardIterator, class T> constexpr ForwardIterator lower_bound(ForwardIterator first, ForwardIterator last, const T& value); template<class ForwardIterator, class T, class Compare> constexpr ForwardIterator lower_bound(ForwardIterator first, ForwardIterator last, const T& value, Compare comp); template<ForwardIterator I, Sentinel<I> S, class T, class Proj = identity, IndirectStrictWeakOrder<const T*, projected<I, Proj>> Comp = ranges::less> constexpr I ranges::lower_bound(I first, S last, const T& value, Comp comp = {}, Proj proj = {}); template<ForwardRange R, class T, class Proj = identity, IndirectStrictWeakOrder<const T*, projected<iterator_t<R>, Proj>> Comp = ranges::less> constexpr safe_iterator_t<R> ranges::lower_bound(R&& r, const T& value, Comp comp = {}, Proj proj = {}); 
Let comp be less{} and proj be identity{} for overloads with no parameters by those names.
Requires: The elements e of [first, last) shall be partitioned with respect to the expression bool(invoke(comp, invoke(proj, e), value)).
Returns: The furthermost iterator i in the range [first, last] such that for every iterator j in the range [first, i), bool(invoke(comp, invoke(proj, *j), value)) is true.
Complexity: At most comparisons and projections.

#### 25.7.3.2upper_­bound[upper.bound]

template<class ForwardIterator, class T> constexpr ForwardIterator upper_bound(ForwardIterator first, ForwardIterator last, const T& value); template<class ForwardIterator, class T, class Compare> constexpr ForwardIterator upper_bound(ForwardIterator first, ForwardIterator last, const T& value, Compare comp); template<ForwardIterator I, Sentinel<I> S, class T, class Proj = identity, IndirectStrictWeakOrder<const T*, projected<I, Proj>> Comp = ranges::less> constexpr I ranges::upper_bound(I first, S last, const T& value, Comp comp = {}, Proj proj = {}); template<ForwardRange R, class T, class Proj = identity, IndirectStrictWeakOrder<const T*, projected<iterator_t<R>, Proj>> Comp = ranges::less> constexpr safe_iterator_t<R> ranges::upper_bound(R&& r, const T& value, Comp comp = {}, Proj proj = {}); 
Let comp be less{} and proj be identity{} for overloads with no parameters by those names.
Requires: The elements e