NAME¶

std::unordered_map::insert_range - std::unordered_map::insert_range

Synopsis¶

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

Inserts a copy of each element in the range 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.

If after the operation the new number of elements is greater than old
max_load_factor() * bucket_count() a rehashing takes place.
If rehashing occurs (due to the insertion), all iterators are invalidated. Otherwise
(no rehashing), iterators are not invalidated.

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(N·(a.size() + 1)).

Notes¶

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

Example¶

// Run this code

#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¶

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