std::swap(std::unordered_map)
From cppreference.com
< cpp | container | unordered map
| Defined in header <unordered_map>
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| template< class Key, class T, class Hash, class KeyEqual, class Alloc > void swap( std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& lhs, |
(since C++11) (until C++17) |
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| template< class Key, class T, class Hash, class KeyEqual, class Alloc > void swap( std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& lhs, |
(since C++17) | |
Specializes the std::swap algorithm for std::unordered_map. Swaps the contents of lhs and rhs. Calls lhs.swap(rhs).
Parameters
| lhs, rhs | - | containers whose contents to swap |
Return value
(none)
Complexity
Constant.
Exceptions
|
noexcept specification:
noexcept(noexcept(lhs.swap(rhs))) |
(since C++17) |
Notes
Although the overloads of std::swap for container adaptors are introduced in C++11, container adaptors can already be swapped by std::swap in C++98. Such calls to std::swap usually have linear time complexity, but better complexity may be provided.
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 << "\n" "bob :"; 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 << "\n" "bob :"; std::for_each(bob.begin(), bob.end(), print); std::cout << '\n'; }
Possible output:
alice: 1:a 2:b 3:c bob : 7:Z 8:Y 9:X 10:W -- SWAP alice: 7:Z 8:Y 9:X 10:W bob : 1:a 2:b 3:c
See also
| (C++11) |
swaps the contents (public member function) |