【剑指Offer】31. 栈的压入、弹出序列

import java.util.*;

public class Solution {
    public boolean IsPopOrder(int [] pushA,int [] popA) {
        int len = pushA.length;
        Stack<Integer> stack = new Stack<>();
        for(int pushIndex = 0, popIndex = 0; pushIndex < len; pushIndex++) {
            stack.push(pushA[pushIndex]);
            while(popIndex < len && !stack.isEmpty()
                 && stack.peek() == popA[popIndex]) {
                stack.pop();
                popIndex++;                
            }
        }
        return stack.isEmpty();
    }
}