24 Containers library [containers]

24.6 Container adaptors [container.adaptors]

24.6.9 Class template flat_map [flat.map]

24.6.9.3 Constructors [flat.map.cons]

flat_map(key_container_type key_cont, mapped_container_type mapped_cont,
         const key_compare& comp = key_compare());

Effects: Initializes c.keys with std::move(key_cont), c.values with std::move(mapped_cont), and compare with comp; sorts the range [begin(), end()) with respect to value_comp(); and finally erases the duplicate elements as if by: auto zv = views::zip(c.keys, c.values); auto it = ranges::unique(zv, key_equiv(compare)).begin(); auto dist = distance(zv.begin(), it); c.keys.erase(c.keys.begin() + dist, c.keys.end()); c.values.erase(c.values.begin() + dist, c.values.end());

Complexity: Linear in N if the container arguments are already sorted with respect to value_comp() and otherwise

N log N

, where N is the value of key_cont.size() before this call.

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flat_map(sorted_unique_t, key_container_type key_cont, mapped_container_type mapped_cont,
         const key_compare& comp = key_compare());

Effects: Initializes c.keys with std::move(key_cont), c.values with std::move(mapped_cont), and compare with comp.

Complexity: Constant.