Queue using two Stacks.cpp

/* 

    Solution by Rahul Surana
    
    ***********************************************************


Implement a Queue using 2 stacks s1 and s2 .
A Query Q is of 2 Types
(i) 1 x (a query of this type means  pushing 'x' into the queue)
(ii) 2   (a query of this type means to pop element from queue and print the poped element)



    ***********************************************************
*/


// { Driver Code Starts
#include<bits/stdc++.h>

using namespace std;

class StackQueue{
private:
    stack<int> s1;
    stack<int> s2;
public:
    void push(int B);
    int pop();

};
int main()
{

    int T;
    cin>>T;
    while(T--)
    {
        StackQueue *sq = new StackQueue();

        int Q;
        cin>>Q;
        while(Q--){
        int QueryType=0;
        cin>>QueryType;
        if(QueryType==1)
        {
            int a;
            cin>>a;
            sq->push(a);
        }else if(QueryType==2){
            cout<<sq->pop()<<" ";

        }
        }
        cout<<endl;
    }


}
// } Driver Code Ends


/* The structure of the class is
class StackQueue{
private:   
    // These are STL stacks ( http://goo.gl/LxlRZQ )
    stack<int> s1;
    stack<int> s2;
public:
    void push(int);
    int pop();
}; */

//Function to push an element in queue by using 2 stacks.
void StackQueue :: push(int x)
{
    // while(!s1.empty()){
    //     int z = s1.top();
    //     s2.push(z);
    //     s1.pop();
    // }
    s1.push(x);
    // while(!s2.empty()){
    //     int z = s2.top();
    //     s1.push(z);
    //     s2.pop();
    // }
}

//Function to pop an element from queue by using 2 stacks.
int StackQueue :: pop()
{
    if(s1.empty()) return -1;
    int ans = -1;
    while(s1.size() != 1){
        int z = s1.top();
        s2.push(z);
        s1.pop();
    }
    ans = s1.top();
    s1.pop();
    while(!s2.empty()){
        int z = s2.top();
        s1.push(z);
        s2.pop();
    }        
    return ans;
}