Merge pull request #1 from Gargee07/Branch-for-Stack-using-two-queues…

…-Code

Solution to Issue Mozilla-Campus-Club-Cummins#56 Stack using two queues

Stack_Using_Queues.java

@@ -0,0 +1,94 @@
+/* 
+ * Implementation of Stack using two Queues
+ */
+package stackImplementation;
+import java.util.*;
+
+
+class Stack{  					// Stack class where all methods of stack are created 
+	Queue<Integer> q1 = new LinkedList<Integer>(); 
+	Queue<Integer> q2 = new LinkedList<Integer>();
+	int size;
+
+	Stack(){
+		size=0;
+	}
+
+	//using Push Operation costly approach
+	void push(int element) {  
+		size++; 
+		q2.add(element);    //adding recently entered element to q2
+
+		while (!q1.isEmpty()) {    
+			q2.add(q1.peek());	 // moving all the elements of q1 to q2 
+			q1.remove(); 
+		} 
+
+		Queue<Integer> temp = q1;   
+		q1 = q2; 				//swapping the queues
+		q2 = temp;
+	}
+
+
+	int pop() {  				// returns and remove the recently entered element
+		if (q1.isEmpty()) { 
+			return -1; } //returns -1 for empty queue
+		else{
+			size--;
+			return q1.remove(); 
+		}
+	}
+
+
+	int top() {    // returns the recently entered element
+		if (q1.isEmpty()) 
+			return -1; 
+		return q1.peek(); 
+	}
+
+
+	int size() {     // returns the size of stack
+		return size;
+	}
+}
+
+public class Stack_Using_Queues {
+
+	public static void main(String[] args) {
+		Scanner input=new Scanner (System.in);
+		Stack stack=new Stack();   //Instantiating Stack class
+		char m;int choice;
+		do {
+
+
+			System.out.println("Enter the choice from the menu");
+			System.out.println(" 1.Push element\n 2.Pop element"); //menu
+			choice=input.nextInt();
+			switch(choice) {
+			case 1:{
+				System.out.println("Enter number:");
+				int x=input.nextInt();
+				stack.push(x);
+				break;
+			}
+			case 2: {
+				System.out.println(stack.pop());
+				break;
+			}
+
+			default: {
+				System.out.println("Enter valid input");
+			}
+			} 
+			System.out.println("Press 'Y' to continue to menu or press 'N' to exit");
+			m=input.next().charAt(0);
+
+			if(m=='n'|| m=='N') {
+				System.out.println("The program has exited successfully");
+				System.exit(0);}
+		}while(m=='y' || m=='Y');
+
+		input.close();
+	}
+
+}