std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::insert_range
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std::unordered_map
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unordered_map::insert_range
(C++23)
(C++17)
(C++17)
(C++20)
(until C++20)
template< container-compatible-range <value_type> R >
void insert_range( R&& rg );
(since C++23) void insert_range( R&& rg );
(constexpr since C++26)
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.
If any of the following conditions is satisfied, the behavior is undefined:
-
value_typeis not EmplaceConstructible intounordered_mapfrom *ranges::begin (rg) - rg and *this overlap.
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.
Contents
[edit] Parameters
[edit] Complexity
Average case \(\scriptsize N\)N, worst case \(\scriptsize O(N \cdot S + N)\)O(N·S+N), where \(\scriptsize S\)S is size() and \(\scriptsize N\)N is ranges::distance (rg).
[edit] Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_containers_ranges |
202202L |
(C++23) | Ranges-aware construction and insertion |
[edit] Example
Run this code
#include <iostream> #include <unordered_map> #include <utility> void println(auto, const auto& 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}