std::vector<T,Allocator>::swap

void swap( vector& other );
 (until C++17) 
void swap( vector& other ) noexcept(/* see below */);
 (since C++17)

Exchanges the contents of the container with those of other. Does not invoke any move, copy, or swap operations on individual elements.

All iterators and references remain valid. The past-the-end iterator is invalidated.

If std::allocator_traits<allocator_type>::propagate_on_container_swap::value is true, then the allocators are exchanged using an unqualified call to non-member swap. Otherwise, they are not swapped (and if get_allocator() != other.get_allocator(), the behavior is undefined). (since C++11)

Parameters

other - container to exchange the contents with

Return value

(none).

Exceptions

(none).

 (until C++17)
noexcept specification:
noexcept(std::allocator_traits<Allocator>::propagate_on_container_swap::value
|| std::allocator_traits<Allocator>::is_always_equal::value)
 (since C++17)

Complexity

Constant.

See also

specializes the std::swap algorithm
(function template)

Example

#include <vector>
#include <iostream>
 
void printVector(std::vector<int>& vec)
{
    for (int a : vec)
    {
        std::cout << a << " ";
    }
}
 
int main()
{
    std::vector<int> v1{1, 2, 3};
    std::vector<int> v2{7, 8, 9};
 
    std::cout << "v1: ";
    printVector(v1);
 
    std::cout << "\nv2: ";
    printVector(v2);
 
    std::cout << "\n-- SWAP\n";
    v2.swap(v1);
 
    std::cout << "v1: ";
    printVector(v1);
 
    std::cout << "\nv2: ";
    printVector(v2);
}

Output:

v1: 1 2 3
v2: 7 8 9
-- SWAP
v1: 7 8 9
v2: 1 2 3

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