栈的压入、弹出序列

bool IsPopOrder(vector<int> pushV,vector<int> popV) {
        stack<int> s;
        int i = 0, j = 0, len1 = pushV.size(), len2 = popV.size();
        while(j < len2){
            while(i < len1 && (s.empty() || s.top() != popV[j])){
                s.push(pushV[i]);
                ++i;
            }
            if(s.top() == popV[j]){
                s.pop();
                ++j;
            }else{
                if(i == len1)break;
            } 
        }
        if(j == len2)return true;
        return false;
    }
};