C++ Stack Library - swap() Function

---

---

Description

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

Declaration

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

C++11

template <class T, class Container>
void swap (stack<T,Container>& stack1, stack<T,Container>& stack2) noexcept;

Parameters

• stack1 − First stack.

• stack2 − Second stack.

Return value

None

Exceptions

This function never throws exception.

Time complexity

Linear i.e. O(n)

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(i + 100);

   swap(s1, 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