剑指offer22 栈的压入、弹出序列

写的一个代码，虽然正确通过了，但我觉得会报vector越界的错误

class Solution {
public:
    bool IsPopOrder(vector<int> pushV,vector<int> popV) {
        int length1 = pushV.size();
        int length2 = popV.size();
        if(length1 <=  || length2 <=  || length1 != length2)
            return false;
        stack<int> sta;
        int current = ;
        for(int i = ;i < length2;i++){
            if(sta.empty()){
                while(pushV[current] != popV[i]){
                    if(current >= length1)
                        return false;
                    sta.push(pushV[current]);
                    current++;
                }
                current++;
            }
            else{
                if(sta.top() == popV[i]){
                    sta.pop();
                }
                else{
                    while(pushV[current] != popV[i]){
                        if(current >= length1)
                            return false;
                        sta.push(pushV[current]);
                        current++;
                    }
                    current++;
                }
            }
        }
        return true;
    }
};