String to Integer (atoi)算法

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

把string转化成int类型

class Solution {public:    int myAtoi(string str) {        long result = 0;        int sign = 1;        int i;        i = str.find_first_not_of(' ');        if(str[i] == '-' || str[i] == '+'){            sign = (str[i] == '+')? 1 : -1;            i++;        }                        while('0'<= str[i] && str[i] <= '9')         {            result = result*10 + (str[i++]-'0');            if(result*sign >= INT_MAX) return INT_MAX;            if(result*sign <= INT_MIN) return INT_MIN;                        }        return result*sign;                    }};

先确定符号位，然后确定数值位，两者相乘即为结果，当结果溢出时，返回所触边界的值。 

tip：可以用find_first_not_of函数确定第一个不为‘ ’的位置