232. Implement Queue using Stacks

     /*
      * 232. Implement Queue using Stacks
      * 2016-6-14 by Mingyang
      * 只用两个stack，每次只用改push得程序，只要这个每次进来一个，就把所有的依次弹入另一个，加入值以后依次弹回来
      * 这里跟implement stack using queue不一样，不用换queue换来换去的哈
      */
     class MyQueue {
         Stack<Integer> queue = new Stack<Integer>();
         Stack<Integer> temp = new Stack<Integer>();
         // Push element x to the back of queue.
         public void push(int x) {    
             while (!queue.empty()) {
                 temp.push(queue.pop());
             }
             queue.push(x);
             while (!temp.empty()) {
                 queue.push(temp.pop());
             }
         }
         // Removes the element from in front of queue.
         public void pop() {
             queue.pop();
         }
         // Get the front element.
         public int peek() {
             return queue.peek();
         }
         // Return whether the queue is empty.
         public boolean empty() {
             return queue.empty();
         }
     }