[leetcode] atoi

第一篇博客，看看可不可以用啦~~

 

 

class Solution {
public:
    int atoi(const char *str) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        const char *p = str;

        int ret = 0;

        bool isPos = 1;

        while(*p == ' ') p++;

        if(*p == '+'){
            isPos = 1;
            p++;
        }else if(* p == '-'){
            isPos = 0;
            p++;
        }

        while(*p){
            if(*p >= '0' && *p <= '9'){
                if(ret > INT_MAX /10 || INT_MAX - ret*10 < *p - '0'){
                    if(isPos) return INT_MAX;
                    else return INT_MIN;
                }
                ret = ret * 10 + *p - '0';

            }else{
                if(isPos) return ret;
                else return -ret;
            }

            p++;
        }

        //if(ret == INT_MAX || ret == INT_MIN) return -ret;

        if(isPos) return ret;
        return -ret;

    }
};