std::swap(std::queue)

 

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Defined in header <queue>
template<class T, class Container > void swap(std::queue<T, Container>& lhs,            std::queue<T, Container>& rhs );		(since C++11) (until C++17)
template<class T, class Container > void swap(std::queue<T, Container>& lhs,            std::queue<T, Container>& rhs )                noexcept(/* see below */);		(since C++17)

Specializes the std::swap algorithm for std::queue. Swaps the contents of lhs and rhs. Calls lhs.swap(rhs).

This overload participates in overload resolution only if std::is_swappable_v<Container> is true.

(since C++17)

Parameters

lhs, rhs

-

containers whose contents to swap

Return value

(none)

Complexity

Same as swapping the underlying containers.

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 <queue>   int main(){std::queue<int> alice;std::queue<int> bob;   auto print =[](constauto& title, constauto& cont){std::cout<< title <<" size="<< cont.size();std::cout<<" front="<< cont.front();std::cout<<" back="<< cont.back()<<'\n';};   for(int i =1; i <4;++i) alice.push(i);for(int i =7; i <11;++i) bob.push(i);   // Print state before swap print("Alice:", alice); print("Bobby:", bob);   std::cout<<"-- SWAP\n";std::swap(alice, bob);   // Print state after swap print("Alice:", alice); print("Bobby:", bob);}

Output:

Alice: size=3 front=1 back=3 Bobby: size=4 front=7 back=10 -- SWAP Alice: size=4 front=7 back=10 Bobby: size=3 front=1 back=3

See also

swap (C++11)

swaps the contents (public member function)