利用辅助栈

public:
    bool IsPopOrder(vector<int> pushV,vector<int> popV) {
        stack<int> stackV;
        int i=0,j=0;
        stackV.push(pushV[0]);
        while(i<pushV.size()&&j<popV.size()){
            if(stackV.empty()){
                i++;
                stackV.push(pushV[i]);
            }
            if(stackV.top()!=popV[j]){
                i++;
                stackV.push(pushV[i]);
                continue;
            }
            stackV.pop();
            j++;
        }
        return stackV.empty();
    }
};