用栈实现队列
1.分析
2.代码
java
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();
*/