std::swap(std::unordered_map)
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< cpp | container | unordered map
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Tables
std::unordered_map
(C++17)
(C++17)
(C++23)
(C++17)
(C++17)
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(until C++20)
std::swap(std::unordered_map)
(C++20)
Deduction guides (C++17)
Defined in header
<unordered_map>
template< class Key, class T, class Hash, class KeyEqual, class Alloc >
(since C++11) void swap( std::unordered_map <Key, T, Hash, KeyEqual, Alloc>& lhs,
(until C++17)
template< class Key, class T, class Hash, class KeyEqual, class Alloc >
(since C++17) void swap( std::unordered_map <Key, T, Hash, KeyEqual, Alloc>& lhs,
std::unordered_map <Key, T, Hash, KeyEqual, Alloc>& rhs )
(constexpr since C++26)
Specializes the std::swap algorithm for std::unordered_map . Swaps the contents of lhs and rhs. Calls lhs.swap(rhs).
[edit] Parameters
lhs, rhs
-
containers whose contents to swap
[edit] Complexity
Constant.
Exceptions
noexcept specification:
(since C++17)noexcept(noexcept(lhs.swap(rhs)))
[edit] Example
Run this code
#include <algorithm> #include <iostream> #include <unordered_map> int main() { std::unordered_map <int, char> alice{{1, 'a'}, {2, 'b'}, {3, 'c'}}; std::unordered_map <int, char> bob{{7, 'Z'}, {8, 'Y'}, {9, 'X'}, {10, 'W'}}; auto print = [](std::pair <const int, char>& n) { std::cout << ' ' << n.first << ':' << n.second; }; // Print state before swap std::cout << "Alice:"; std::for_each (alice.begin(), alice.end(), print); std::cout << "\nBobby:"; std::for_each (bob.begin(), bob.end(), print); std::cout << '\n'; std::cout << "-- SWAP\n"; std::swap (alice, bob); // Print state after swap std::cout << "Alice:"; std::for_each (alice.begin(), alice.end(), print); std::cout << "\nBobby:"; std::for_each (bob.begin(), bob.end(), print); std::cout << '\n'; }
Possible output:
Alice: 1:a 2:b 3:c Bobby: 7:Z 8:Y 9:X 10:W -- SWAP Alice: 7:Z 8:Y 9:X 10:W Bobby: 1:a 2:b 3:c