std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::insert_range

From cppreference.com

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

Inserts a copy of each element of rg if and only if there is no element with key equivalent to the key of that element in *this.

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.
Type requirements
-
value_type must be EmplaceConstructible into unordered_map from *ranges::begin(rg). Otherwise, the behavior is undefined.

Return value

(none)

Complexity

Average case O(N), where N is ranges::distance(rg), worst case O((a.size() + 1))

Notes

Feature-test macro Value Std Comment
__cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion

Example

#include <iostream>
#include <unordered_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::unordered_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);
}

Possible output:

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

See also

(C++11)
inserts elements or nodes (since C++17)
(public member function)