Leetcode 8. String to Integer (atoi) 字串轉整數 (atoi)

 使用正規表示式非常簡單，程式碼簡短，速度也不慢（68ms）在python中打敗94%

class Solution:
    def myAtoi(self, str):
        """
        :type str: str
        :rtype: int
        """
        import re
        pattern1 = re.compile(r'^\s{0,}([+-]?\d+)')
        match1 = pattern1.match(str)
        if match1:
            number_str = match1.group()
            number = int(number_str)
        else:
            number = 0

        if number < -1*2**31:
            return -1*2**31
        elif number > 2**31-1:
            return 2**31 - 1
        else:
            return number