Merge pull request #118 from nimit17/ReverseStack

Added algorithm to reverse a stack

Author: AnupKumarPanwar

Misc/ReverseStackUsingRecursion.java

@@ -0,0 +1,74 @@
+/* Program to reverse a Stack using Recursion*/
+
+
+import java.util.Stack;
+
+public class ReverseStackUsingRecursion {
+
+    //Stack
+    private static Stack<Integer> stack=new Stack<>();
+
+    //Main function
+    public static void main(String[] args) {
+        //To Create a Dummy Stack containing integers from 0-9
+        for(int i=0;i<10;i++)
+        {
+            stack.push(i);
+        }
+        System.out.println("STACK");
+
+        //To print that dummy Stack
+        for(int k=9;k>=0;k--)
+        {
+            System.out.println(k);
+        }
+
+        //Reverse Function called
+        reverseUsingRecursion(stack);
+
+        System.out.println("REVERSED STACK : ");
+        //To print reversed  stack
+        while (!stack.isEmpty())
+        {
+            System.out.println(stack.pop());
+        }
+
+
+    }
+
+    //Function Used to reverse Stack Using Recursion
+    private static void reverseUsingRecursion(Stack<Integer> stack) {
+        if(stack.isEmpty()) // If stack is empty then return
+        {
+            return;
+        }
+        /* All items are stored in call stack until we reach the end*/
+
+        int temptop=stack.peek();
+        stack.pop();
+        reverseUsingRecursion(stack); //Recursion call
+        insertAtEnd(temptop); // Insert items held in call stack one by one into stack
+    }
+
+    //Function used to insert element at the end of stack
+    private static void insertAtEnd(int temptop) {
+        if(stack.isEmpty())
+        {
+            stack.push(temptop); // If stack is empty push the element
+        }
+        else {
+            int temp = stack.peek(); /* All the items are stored in call stack until we reach end*/
+            stack.pop();
+
+            insertAtEnd(temptop); //Recursive call
+
+            stack.push(temp);
+        }
+
+    }
+
+
+
+
+
+}