[leetcode 008] 字符串转换整数

实现一个能将字符串转换成整数的函数。

示例：

输入："42"

输出：42

输入：“   -42”

输出：-42

输入："words with 987"

输出：0

代码：

class Solution(object):
    def myAtoi(self, str):
        """
        :type str: str
        :rtype: int
        """
        sign = 1
        max_int, min_int = 2147483647, -2147483648
        result, pos = 0, 0
        ls = len(str)

        while pos < ls and str[pos] == ' ':
            pos += 1
          if pos < ls and str[pos] == '-':
              sign = -1
              pos += 1
          elif pos < ls and str[pos] == '+':
              pos += 1

        while pos < ls and ord(str[pos]) >= ord('0') and ord(str[pos]) <= ord('9'):
            num = ord(str[pos]) - ord('0')

            if result > max_int / 10 or ( result == max_int / 10 and num >= 8):
                if sign == -1:
                    return min_int
                return max_int
            result = result * 10 + num
            pos += 1
        return sign * result

参考链接：https://github.com/qiyuangong/leetcode/blob/master/python/008_String_to_Integer(atoi).py