std::multiset swap() method
- od C++17
- do C++17
// Non const version only
void swap( multiset& other ) noexcept(/* see below */);
// Non const version only
void swap( multiset& other );
Exchanges the contents of the container with those of other
. Does not invoke any move, copy, or swap operations on individual elements.
The past-the-end iterator is invalidated.
All other iterators and references remain valid.
The Compare
objects must be Swappable
, and they are exchanged using unqualified call to non-member swap.
- 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.
If get_allocator() != other.get_allocator()
, the behavior is undefined.
Parameters
other
- container to exchange the contents with
Return value
(none)
Exceptions
- od C++17
- do C++17
noexcept(std::allocator_traits<Allocator>::is_always_equal::value
&& std::is_nothrow_swappable<Compare>::value)
Compare
objects. Complexity
Constant - O(1).
Example
#include <functional>
#include <iostream>
#include <set>
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::multiset<int> a1{3, 1, 3, 2}, a2{5, 4, 5};
auto it1 = std::next(a1.begin());
auto it2 = std::next(a2.begin());
const int& ref1 = *(a1.begin());
const int& ref2 = *(a2.begin());
std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
a1.swap(a2);
std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
// Note that every iterator referring to an element in one container before the swap
// refers to the same element in the other container after the swap. Same is true
// for references.
struct Cmp : std::less<int> {
int id{};
Cmp(int i) : id{i} { }
};
std::multiset<int, Cmp> s1{ {2, 2, 1, 1}, Cmp{6} }, s2{ {4, 4, 3, 3}, Cmp{9} };
std::cout << s1 << s2 << s1.key_comp().id << ' ' << s2.key_comp().id << '\n';
s1.swap(s2);
std::cout << s1 << s2 << s1.key_comp().id << ' ' << s2.key_comp().id << '\n';
// So, comparator objects (Cmp) are also exchanged after the swap.
}
{ 1 2 3 3 } { 4 5 5 } 2 5 1 4
{ 4 5 5 } { 1 2 3 3 } 2 5 1 4
{ 1 1 2 2 } { 3 3 4 4 } 6 9
{ 3 3 4 4 } { 1 1 2 2 } 9 6
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