给定入栈序列，判断出栈序列是否合法

#include <iostream>
#include <stack>
using namespace std;

bool isPopOrder(int* pushOrder, int* popOrder, int len){
    if(len<=0)
        return false;

    int* pushIndex=pushOrder,*popIndex=popOrder;
    stack<int> s;
    while(popIndex!=popOrder+len){
        if(!s.empty()&&s.top()==*popIndex){   //从栈顶查找
            s.pop();
            ++popIndex;
        }else{                                //从未入栈的序列查找
            while((pushIndex-pushOrder<len)&&(*pushIndex!=*popIndex)){
                s.push(*pushIndex);
                ++pushIndex;
            }
            if(pushIndex-pushOrder<len&&(*pushIndex==*popIndex)){   //在未入栈的元素中找到了需要出栈的元素
                ++popIndex;
            }
            else                            //没有找到
                return false;
        }
    }
    return true;
}

int main(){
   int pushOrder[5]={1,3,2,4,5};
   int popOrderRight[5]={5,4,2,3,1};
   int popOrderWrong[5]={3,1,5,2,4};

   if(isPopOrder(pushOrder,popOrderRight,5))
       cout<<"popOrderRight is right"<<endl;
   else
       cout<<"popOrderRight is wrong"<<endl;

   if(isPopOrder(pushOrder,popOrderWrong,5))
       cout<<"popOrderWrong is right"<<endl;
   else
       cout<<"popOrderWrong is wrong"<<endl;

popOrderRight is right
popOrderWrong is wrong