NAME

std::vector::swap - std::vector::swap

Synopsis

void swap( vector& other ); (until C++17)
void swap( vector& other ) noexcept(/* see below */); (since C++17)
(until C++20)
constexpr void swap( vector& other ) noexcept(/* see below */); (since C++20)

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 (since
non-member swap. Otherwise, they are not swapped (and if get_allocator() != C++11)
other.get_allocator(), the behavior is undefined).

Parameters

other - container to exchange the contents with

Return value

(none)

Exceptions

(none) (until
C++17)
noexcept specification: (since
noexcept(std::allocator_traits<Allocator>::propagate_on_container_swap::value C++17)
|| std::allocator_traits<Allocator>::is_always_equal::value)

Complexity

Constant.

Example

// Run this code

#include <iostream>
#include <vector>

template<class Os, class Co> Os& operator<<(Os& os, const Co& co) {
os << "{";
for (auto const& i : co) { os << ' ' << i; }
return os << " } ";
}

int main()
{
std::vector<int> a1{1, 2, 3}, a2{4, 5};

auto it1 = std::next(a1.begin());
auto it2 = std::next(a2.begin());

int& ref1 = a1.front();
int& ref2 = a2.front();

std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
a1.swap(a2);
std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';

// Note that after swap the iterators and references stay associated with their
// original elements, e.g. it1 that pointed to an element in 'a1' with value 2
// still points to the same element, though this element was moved into 'a2'.
}

Output:

{ 1 2 3 } { 4 5 } 2 5 1 4
{ 4 5 } { 1 2 3 } 2 5 1 4