swaping two stacks using STL

// CPP program to illustrate
// Implementation of swap() function
#include <stack>
#include <iostream>
using namespace std;

int main()
{
// stack container declaration
stack<int> mystack1;
stack<int> mystack2;

// pushing elements into first stack
mystack1.push(1);
mystack1.push(2);
mystack1.push(3);
mystack1.push(4);

// pushing elements into 2nd stack
mystack2.push(3);
mystack2.push(5);
mystack2.push(7);
mystack2.push(9);

// using swap() function to swap elements of stacks
mystack1.swap(mystack2);

// printing the first stack
cout<<"mystack1 = ";
while (!mystack1.empty()) {
cout<<mystack1.top()<<" ";
mystack1.pop();
}

// printing the second stack
cout<<endl<<"mystack2 = ";
while (!mystack2.empty()) {
cout<<mystack2.top()<<" ";
mystack2.pop();
}
return 0;
}