std::swap(std::vector)

Defined in header `<vector>`
template< class T, class Alloc > void swap( std::vector<T, Alloc>& lhs, std::vector<T, Alloc>& rhs );		(until C++17)
template< class T, class Alloc > void swap( std::vector<T, Alloc>& lhs, std::vector<T, Alloc>& rhs ) noexcept(/* see below */);		(since C++17) (until C++20)
template< class T, class Alloc > constexpr void swap( std::vector<T, Alloc>& lhs, std::vector<T, Alloc>& rhs ) noexcept(/* see below */);		(since C++20)

Specializes the std::swap algorithm for std::vector. 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 <vector>
 
int main()
{
    std::vector<int> alice{1, 2, 3};
    std::vector<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 << "\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';
}

Output:

alice: 1 2 3
bob  : 7 8 9 10
-- SWAP
alice: 7 8 9 10
bob  : 1 2 3

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