剑指offer 22 栈的压入、弹出序列

class Solution {
public:
    bool IsPopOrder(vector<int> pushV,vector<int> popV) {
        bool result=false;
        int n1=pushV.size();
        int n2=popV.size();
        if(!n1||!n2)
            return result;
        int push_index=0;
        int pop_index=0;
        stack<int> s;
        s.push(pushV[push_index++]);
        while(pop_index<n2)
        {
            while(s.top()!=popV[pop_index]&&push_index<n1)
                s.push(pushV[push_index++]);
            if(s.top()==popV[pop_index])
            {
                s.pop();
                pop_index++;
            }
            else
                break;
        }
        if(pop_index==n2)
            result=true;
        return result;

    }
};

*不可以在堆栈为空时，使用s.top()函数，会发生未知！

*要注意边界条件！！