Facebook Page Twitter Page LinkedIn Page
× C++ Standard Library C++ STL Library


The C++ queue::swap function is used to exchange all elements of one queue with all elements of another queue. To apply this function, the data-type of both queues must be same, although the size may differ.

Syntax

template <class T, class Container>
  void swap (queue<T,Container>& lhs, 
             queue<T,Container>& rhs) 
             noexcept(noexcept(lhs.swap(rhs)));

Parameters

lhs First queue.
rhs Second queue.

Return Value

None.

Time Complexity

Constant i.e, Θ(1).

Example:

In the below example, the queue::swap function is used to exchange all elements of queue que1 with all elements of queue que2.

#include <iostream>
#include <queue>
using namespace std;
 
int main (){
  queue<int> que1, que2;

  //add new elements in the que1
  que1.push(10);
  que1.push(20);
  que1.push(30);
  que1.push(40);
  que1.push(50);

  //add new elements in the que2
  que2.push(5);
  que2.push(55);
  que2.push(555);

  swap(que1, que2);

  cout<<"After Swapping, The que1 contains:";
  while (!que1.empty()) {
    cout<<" "<<que1.front();
    que1.pop();
  }
  cout<<"\nAfter Swapping, The que2 contains:";
  while (!que2.empty()) {
    cout<<" "<<que2.front();
    que2.pop();
  }
  return 0;
}

The output of the above code will be:

After Swapping, The que1 contains: 5 55 555
After Swapping, The que2 contains: 10 20 30 40 50

❮ C++ <queue> Library