LeetCode

 8. String to Integer (atoi)

Problem's Link

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Mean: 

给你一个字符串，让你将其转换为数字.

analyse:

注意细节，坑点有点多.

Time complexity: O(N)

 

view code

class Solution
{
public:
   int myAtoi(string str)
   {
       int ret = 0, sign = 1, i = str.find_first_not_of(' '), base = INT_MAX / 10;
       if (str[i] == '+' || str[i] == '-') sign = str[i++] == '+' ?: -1;
       while (isdigit(str[i]))
       {
           if (ret > base || (ret == base && str[i] - '0' > 7))
               return sign > 0 ? INT_MAX : INT_MIN;
           ret = 10 * ret + (str[i++] - '0');
       }
       return sign * ret;
   }
};