C++ Stack Library - swap() Function

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Description

The C++ function std::stack::swap() exchanges the contents of the two size and changes the size of stack if necessary.

Declaration

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

C++11

void swap (stack& x) noexcept;

Parameters

x − Another stack 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::stack::swap() function.

#include <iostream>
#include <stack>

using namespace std;

int main(void) {
   stack<int> s1;
   stack<int> s2;

   for (int i = 0; i < 5; ++i)
      s1.push(i + 1);

   for (int i = 0; i < 3; ++i)
      s2.push(100 + i);

   s1.swap(s2);

   cout << "Contents of stack s1 after swap operation" << endl;
   while (!s1.empty()) {
      cout << s1.top() << endl;
      s1.pop();
   }

   cout << endl;
   cout << "Contents of stack s2 after swap operation" << endl;
   while (!s2.empty()) {
      cout << s2.top() << endl;
      s2.pop();
   }

   return 0;
}

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

Contents of stack s1 after swap operation
102
101
100
Contents of stack s2 after swap operation
5
4
3
2
1