剑指21.栈的压入、弹出序列

import java.util.ArrayList;
import java.util.Stack;
public class Solution {
    public boolean IsPopOrder(int [] pushA,int [] popA) {
        if (pushA.length != popA.length) return false;
        if (pushA.length == 0) return true;
        Stack<Integer> stack = new Stack<>();
        stack.push(pushA[0]); //辅助栈初始化
        int index = 1;
        for (int i = 0; i < popA.length; i++){
            while (stack.peek() != popA[i] && index < pushA.length){
                stack.push(pushA[index++]);
            }
            if (stack.peek() == popA[i]){
                stack.pop();
                continue;
            }
            return false;
        }
        return true;
    }
}