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std::swap(std::unordered_set) - cppreference.com

From cppreference.com

Defined in header <unordered_set>

template< class Key, class Hash, class KeyEqual, class Alloc > void swap( std::unordered_set<Key, Hash, KeyEqual, Alloc>& lhs, std::unordered_set<Key, Hash, KeyEqual, Alloc>& rhs );

 (since C++11)
(until C++17)

template< class Key, class Hash, class KeyEqual, class Alloc > void swap( std::unordered_set<Key, Hash, KeyEqual, Alloc>& lhs, std::unordered_set<Key, Hash, KeyEqual, Alloc>& rhs ) noexcept(/* see below */);

 (since C++17)

Specializes the std::swap algorithm for std::unordered_set. 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)

Example

#include <algorithm>
#include <iostream>
#include <unordered_set>

int main()
{
    std::unordered_set<int> alice{1, 2, 3};
    std::unordered_set<int> bob{7, 8, 9, 10};

    auto print = [](const int& n) { std::cout << ' ' << n; };

    // 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 2 3
Bobby: 7 8 9 10
-- SWAP
Alice: 7 8 9 10
Bobby: 1 2 3

See also

swaps the contents
(public member function) [edit]