Create StackUsingQueue

StackUsingQueue

@@ -0,0 +1,85 @@
+/* Program to implement a stack using 
+two queue */
+#include<bits/stdc++.h> 
+
+using namespace std; 
+
+class Stack 
+{ 
+	// Two inbuilt queues 
+	queue<int> q1, q2; 
+
+	// To maintain current number of 
+	// elements 
+	int curr_size; 
+
+	public: 
+	Stack() 
+	{ 
+		curr_size = 0; 
+	} 
+
+	void push(int x) 
+	{ 
+		curr_size++; 
+
+		// Push x first in empty q2 
+		q2.push(x); 
+
+		// Push all the remaining 
+		// elements in q1 to q2. 
+		while (!q1.empty()) 
+		{ 
+			q2.push(q1.front()); 
+			q1.pop(); 
+		} 
+
+		// swap the names of two queues 
+		queue<int> q = q1; 
+		q1 = q2; 
+		q2 = q; 
+	} 
+
+	void pop(){ 
+
+		// if no elements are there in q1 
+		if (q1.empty()) 
+			return ; 
+		q1.pop(); 
+		curr_size--; 
+	} 
+
+	int top() 
+	{ 
+		if (q1.empty()) 
+			return -1; 
+		return q1.front(); 
+	} 
+
+	int size() 
+	{ 
+		return curr_size; 
+	} 
+}; 
+
+// driver code 
+int main() 
+{ 
+	Stack s; 
+	s.push(1); 
+	s.push(2); 
+	s.push(3); 
+
+	cout << "current size: " << s.size() 
+		<< endl; 
+	cout << s.top() << endl; 
+	s.pop(); 
+	cout << s.top() << endl; 
+	s.pop(); 
+	cout << s.top() << endl; 
+
+	cout << "current size: " << s.size() 
+		<< endl; 
+	return 0; 
+} 
+// This code is contributed by Chhavi