package question;

import java.util.EmptyStackException;
import java.util.Stack;

/*
 @author: Roderland
 @create: 2020年08月18日---20:13
*/

public class Question232 {
 public static void main(String[] args) {
 MyQueue queue = new MyQueue();

 queue.push(1);
 queue.push(2);
 queue.peek(); // 返回 1
 queue.pop(); // 返回 1
 queue.empty(); // 返回 false

 }
}

class MyQueue {

 Stack<Integer> pushStack = new Stack<>();
 Stack<Integer> popStack = new Stack<>();

 /** Initialize your data structure here. */
 public MyQueue() {

 }

 /** Push element x to the back of queue. */
 public void push(int x) {
 pushStack.push(x);
 }

 /** Removes the element from in front of queue and returns that element. */
 public int pop() {
 if (empty()) throw new EmptyStackException();
 if (popStack.isEmpty()) {
 while (!pushStack.isEmpty()) {
 popStack.push(pushStack.pop());
 }
 }
 return popStack.pop();
 }

 /** Get the front element. */
 public int peek() {
 if (empty()) throw new EmptyStackException();
 if (popStack.isEmpty()) {
 while (!pushStack.isEmpty()) {
 popStack.push(pushStack.pop());
 }
 }
 return popStack.peek();
 }

 /** Returns whether the queue is empty. */
 public boolean empty() {
 return pushStack.isEmpty()&&popStack.isEmpty();
 }

}