std::vector swap() method
- od C++20
- od C++17
- do C++17
// Non const version only
constexpr void swap( vector& other ) noexcept(/* see below */);
// Non const version only
void swap( vector& other ) noexcept(/* see below */);
// Non-const version only
void swap( vector& other );
Exchanges the contents of the container with those of other
. Does not invoke any move, copy, or swap operations on individual elements.
Invalidation
The past-the-end iterator is invalidated.
All other iterators and references remain valid.
- od C++11
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).Parameters
other
- the container to exchange the contents with
Return value
(none)
Exceptions
- od C++17
- do C++17
noexcept(std::allocator_traits<Allocator>::propagate_on_container_swap::value
|| std::allocator_traits<Allocator>::is_always_equal::value)
(none)
Complexity
Constant - O(1).
Example
Main.cpp
#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
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