Implement Queue using Stacks : Accepted

Author: gouthampradhan

README.md

@@ -148,6 +148,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [Min Stack](problems/src/stack/MinStack.java) (Easy)
 - [Valid Parentheses](problems/src/stack/ValidParentheses.java) (Easy)
 - [Largest Rectangle In Histogram](problems/src/stack/LargestRectangleInHistogram.java) (Hard)
+- [Implement Queue using Stacks](problems/src/stack/MyQueue.java) (Easy)
 
 #### [String](problems/src/string)
 

problems/src/stack/MyQueue.java

@@ -0,0 +1,76 @@
+package stack;
+
+import java.util.Stack;
+
+/**
+ * Created by gouthamvidyapradhan on 29/07/2017.
+ * Implement the following operations of a queue using stacks.
+
+ push(x) -- Push element x to the back of queue.
+ pop() -- Removes the element from in front of queue.
+ peek() -- Get the front element.
+ empty() -- Return whether the queue is empty.
+
+ Notes:
+ You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.
+ Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
+ You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).
+ */
+public class MyQueue {
+
+    private Stack<Integer> stack;
+    public static void main(String[] args) throws Exception{
+        MyQueue myQueue = new MyQueue();
+        myQueue.push(5);
+        myQueue.push(12);
+        myQueue.push(7);
+        myQueue.push(9);
+        System.out.println(myQueue.peek());
+        System.out.println(myQueue.pop());
+        myQueue.push(56);
+        myQueue.push(53);
+        System.out.println(myQueue.pop());
+    }
+
+    /** Initialize your data structure here. */
+    public MyQueue() {
+        stack = new Stack<>();
+    }
+
+    /** Push element x to the back of queue. */
+    public void push(int x) {
+        stack.push(x);
+    }
+
+    /** Removes the element from in front of queue and returns that element. */
+    public int pop() {
+        Stack<Integer> auxStack = new Stack<>();
+        while(!stack.isEmpty()){
+            auxStack.push(stack.pop());
+        }
+        int result = auxStack.pop();
+        while(!auxStack.isEmpty()){
+            stack.push(auxStack.pop());
+        }
+        return result;
+    }
+
+    /** Get the front element. */
+    public int peek() {
+        Stack<Integer> auxStack = new Stack<>();
+        while(!stack.isEmpty()){
+            auxStack.push(stack.pop());
+        }
+        int result = auxStack.peek();
+        while(!auxStack.isEmpty()){
+            stack.push(auxStack.pop());
+        }
+        return result;
+    }
+
+    /** Returns whether the queue is empty. */
+    public boolean empty() {
+        return stack.isEmpty();
+    }
+
+}