stack using queue.cpp

/*
///////////////////////////////////////////
//Question/Info

Stack using two queues
Easy Accuracy: 40.49% Submissions: 56708 Points: 2
Implement a Stack using two queues q1 and q2.

Example 1:

Input:
push(2)
push(3)
pop()
push(4)
pop()
Output: 3 4
Explanation:
push(2) the stack will be {2}
push(3) the stack will be {2 3}
pop()   poped element will be 3 the
        stack will be {2}
push(4) the stack will be {2 4}
pop()   poped element will be 4
Example 2:

Input:
push(2)
pop()
pop()
push(3)
Output: 2 -1
Your Task:

Since this is a function problem, you don't need to take inputs. You are required to complete the two methods push() which takes an integer 'x' as input denoting the element to be pushed into the stack and pop() which returns the integer poped out from the stack(-1 if the stack is empty).

Expected Time Complexity: O(1) for push() and O(N) for pop() (or vice-versa).
Expected Auxiliary Space: O(1) for both push() and pop().

Constraints:
1 <= Number of queries <= 100
1 <= values of the stack <= 100

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author: srj_v
///////////////////////////////////////////
*/

#include <bits/stdc++.h>
using namespace std;

// #define int 		   long long int
#define sbit(x) 	   __builtin_popcount(x)
#define pb(x) 		   push_back(x)
#define mp(x,y) 	   make_pair(x,y)
#define eb(x) 		   emplace_back(x)
#define ct(x) 		   cout << x << "\n";
#define ct2(x,y) 	   cout << x << " " << y << "\n";
#define tc(x) 		   cout << x << " ";
#define tc2(x,y) 	   cout << x << " " << y << " ";
#define forn(i,n) 	   for(int i = 0; i < (int)(n); ++i)
#define forx(i,x,n)    for(int i = x; i < (int)(n); ++i)
#define nfor(i,n)      for(int i = n-1; i >= 0; --i)
#define all(v) 		   v.begin(),v.end()
#define fsp(x,y)       fixed << setprecision(y) << x
#define PI 			   3.1415926535897932384626433832795
#define MOD 		   1000000007 // (1e9+7)
#define pii 		   pair<int,int>
#define pis 		   pair<int,string>
#define vi  		   vector<int>
#define vii 		   vector<pii>
#define mii 		   map<int,int>
#define p_q            priority_queue // priority_queue<int> (&) priority_queue< int,vi,greater<int> >
#define _IOS      	   ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

typedef long double ld;
typedef long long int lli;

#pragma GCC optimize("Ofast")

void c_p_c()
{
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
}


int32_t main() {
///////////
	c_p_c();
///////////
	_IOS
//////////

	// code

	/*
	int t ; cin >> t; while(t--){}
	*/


	/* The structure of the class is
	class QueueStack{
	private:
	    queue<int> q1;
	    queue<int> q2;
	public:
	    void push(int);
	    int pop();
	};
	 */

//Function to push an element into stack using two queues.
	void QueueStack :: push(int x)
	{
		// Your Code

		q1.push(x);
	}

//Function to pop an element from stack using two queues.
	int QueueStack :: pop()
	{
		// Your Code

		if (q1.empty()) {
			return -1;
		}

		while (q1.size() != 1) {

			q2.push(q1.front());
			q1.pop();
		}

		int x = q1.front();
		q1.pop();

		while (!q2.empty()) {

			q1.push(q2.front());
			q2.pop();

		}

		return x;

	}




// cerr << "time: " << clock() << " ms" << '\n';
	return 0;
}