std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>::insert_range

template< container-compatible-range<value_type> R > void insert_range( R&& rg );		(since C++23)

Inserts a copy of each element in the range rg into underlying containers c as if by:

for (const auto& e : rg)
{
    c.keys.insert(c.keys.end(), e.first);
    c.values.insert(c.values.end(), e.second);
}

Then, sorts the range of newly inserted elements with respect to value_comp(). Merges the resulting sorted range and the sorted range of pre-existing elements into a single sorted range. 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 = std::distance(zv.begin(), it);
c.keys.erase(c.keys.begin() + dist, c.keys.end());
c.values.erase(c.values.begin() + dist, c.values.end());

Each iterator in the range rg is dereferenced exactly once. The behavior is undefined if rg overlaps with the container.

Parameters

rg - a container compatible range, that is, an input_range whose elements are convertible to T

Return value

(none)

Complexity

N + M·log(M), where N is size() before the operation and M is ranges::distance(rg).

Notes

Since insert_range performs an in-place merge operation, that may allocate memory.

Example

Run this code

#include <iostream>
#include <flat_map>
#include <utility>
 
void println(auto, auto const& container)
{
    for (const auto& [key, value] : container)
        std::cout << '{' << key << ',' << value << '}' << ' ';
    std::cout << '\n';
}
 
int main()
{
    auto container = std::flat_map{std::pair{1, 11}, {3, 33}, {2, 22}, {4, 44}};
    const auto rg = {std::pair{-1, -11}, {3, -33}, {-2, -22}};
#ifdef __cpp_lib_containers_ranges
    container.insert_range(rg);
#else
    container.insert(rg.begin(), rg.end());
#endif
    println("{}", container);
}

Output:

{-2,-22} {-1,-11} {1,11} {2,22} {3,33} {4,44}

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