leetcode8

public class Solution {
    public int MyAtoi(string str) {
        int index = , sign = , total = ;
            //1. Empty string
            if (str.Length == )
            {
                return ;
            }
            //2. Remove Spaces
            while (str[index] == ' ' && index < str.Length)
            {
                index++;
            }

            //3. Handle signs
            if (str[index] == '+' || str[index] == '-')
            {
                sign = str[index] == '+' ?  : -;
                index++;
            }

            //4. Convert number and avoid overflow
            while (index < str.Length)
            {
                int digit = str[index] - '';
                if (digit <  || digit > ) break;

                //check if total will be overflow after 10 times and add digit
                if (int.MaxValue /  < total || int.MaxValue /  == total && int.MaxValue %  < digit)
                {
                    return sign ==  ? int.MaxValue : int.MinValue;
                }

                total =  * total + digit;
                index++;
            }
            return total * sign;
    }
}

https://leetcode.com/problems/string-to-integer-atoi/#/description

补充一个python的实现：

 class Solution:
     def myAtoi(self, string: str) -> int:
         string = string.strip()
         n = len(string)
         if n == :
             return
         sign =
         convertStr = ''
         firstNum = False
         for i in range(n):
             c = ord(string[i]) - ord('')
             if not firstNum:
                 if string[i] == '+' and sign == :
                     sign =
                 elif string[i] == '-' and sign == :
                     sign = -
                 elif c >=  and c <= :
                     firstNum = True
                     if sign == :
                         sign =
                     convertStr += str(c)
                 else:
                     convertStr = ''
                     break
             else:
                 if c >=  and c <= :
                     convertStr += str(c)
                 else:
                     break
         r = int(convertStr) * sign
         if r >  **  - :
             r =  **  -
         elif r < -( ** ):
             r = -( ** )
         return r