C++ Queue Library - swap() Function



Description

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

Declaration

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

C++11

void swap (priority_queue& x) noexcept;

Parameters

x − Another prioriy_queue object of same type.

Return value

None.

Exceptions

This member function never throws exception.

Time complexity

Constant i.e. O(1)

Example

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

#include <iostream>
#include <queue>

using namespace std;

int main(void) {
   auto it1 = {3, 1, 5, 2, 4};
   auto it2 = {5, 2, 4};
   priority_queue<int> q1(less<int>(), it1);
   priority_queue<int> q2(less<int>(), it2);

   q1.swap(q2);

   cout << "Contents of q1 after swap operation" << endl;
   while (!q1.empty()) {
      cout << q1.top() << endl;
      q1.pop();
   }

   cout << "Contents of q2 after swap operation" << endl;
   while (!q2.empty()) {
      cout << q2.top() << endl;
      q2.pop();
   }

   return 0;
}

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

Contents of q1 after swap operation
5
4
2
Contents of q2 after swap operation
5
4
3
2
1
queue.htm
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