1.分析

2.代码

class MyQueue {private Stack<Integer> s1;private Stack<Integer> s2;public MyQueue() {s1 = new Stack<>();s2 = new Stack<>();}public void push(int x) {s1.push(x);}public int pop() {if(empty()){return -1;}if(s2.empty()){while(!s1.empty()){s2.push(s1.pop());}}return s2.pop();}public int peek() {if(empty()){return -1;}if(s2.empty()){while(!s1.empty()){s2.push(s1.pop());}}return s2.peek();}public boolean empty() {return s1.empty()&&s2.empty();}
}/*** Your MyQueue object will be instantiated and called as such:* MyQueue obj = new MyQueue();* obj.push(x);* int param_2 = obj.pop();* int param_3 = obj.peek();* boolean param_4 = obj.empty();*/