C++ Queue Library - swap() Function

Description

The C++ function std::queue::swap() exchanges the contents of queue with contents of another queue x.

Declaration

Following is the declaration for std::queue::swap() function form std::queue header.

C++11

void swap (queue& x) noexcept;

Parameters

x − Another queue object of same type.

Return value

None

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::queue::swap() function.

#include <iostream>
#include <queue>

using namespace std;

int main(void) {
   queue<int> q1, q2;

   for (int i = 0; i < 5; ++i)
      q1.push(i + 1);

   for (int i = 0; i < 2; ++i)
      q2.push(i + 150);

   q1.swap(q2);

   cout << "Content of q1 and q2 after swap operation" << endl;;
   while (!q1.empty()) {
      cout << q1.front() << endl;
      q1.pop();
   }

   cout << endl << endl;

   while (!q2.empty()) {
      cout << q2.front() << endl;
      q2.pop();
   }

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Content of q1 and q2 after swap operation
150
151
1
2
3
4
5