【字符串】面试题67. 把字符串转换成整数(atoi)

题目：

 

 

 

解答:

class Solution {
public:
    int strToInt(string str) 
    {
        if (str.size() == 0)
        {
            return 0;
        }

        int i = 0;
        int minus = 1;

        // skip spaces
        while (str[i] == ' ')
        {
            i++;
        }

        // get sign
        if (str[i] == '-')
        {
            minus = -1;
            i++;
        }
        else if (str[i] == '+')
        {
            minus = 1;
            i++;
        }

        // convert numbers
        int num = 0;
        while (isdigit(str[i]))
        {
            // 214748364 = INT_MAX / 10
            if ((num == 214748364) && ((str[i] - '0') > 7) || (num > 214748364))
            {
                return (minus > 0) ? INT_MAX : INT_MIN;
            } 
            num = 10 * num + (str[i] - '0');
            i++;
        }

        return (minus > 0) ? num : -num;
    }
};