leetcode8 字符串转换整数

class Solution {
public:
    int myAtoi(string s) 
    {
        int i = 0;
        long result = 0;
        bool zheng = true;
        while(s[i] == ‘ ‘)
        i++;
        if(s[i] == ‘+‘ || s[i] == ‘-‘ )
        {
            if(s[i] == ‘-‘)
            zheng = false;
            i++;
        }
        while(isdigit(s[i]))
        {
            result = s[i]-‘0‘ + result*10;
            if(result>pow(2,31)-1)
            break;
            i++;
        }
        if(!zheng)
        result = -1*result;
        if(result>pow(2,31)-1)
        result = pow(2,31)-1;
        else if(result<-1*pow(2,31))
        result = -1*pow(2,31);
        return result;
    }
};