8 String to Integer

思路就是简单模拟，没有复杂的东西

class Solution(object):
    def myAtoi(self, str):
        """
        :type str: str
        :rtype: int
        """
        l = len(str)
        str = str.strip()
        if not str:
            return 0
        flag = 1
        if str[0] == '-':
            flag = -1
            str = str[1:]
        elif str[0] == '+':
            flag = 1
            str = str[1:]
        elif str[0] in ['0','1','2','3','4','5','6','7','8','9']:
            pass
        else:
            return 0
        c = 0
        for i in range(len(str)):
            if str[i] in ['0','1','2','3','4','5','6','7','8','9']:
                d = ord(str[i]) -ord('0')
                c = 10*c+d
            else:
                break
        c = c*flag
        if c >= 2**31-1:
            return 2**31-1
        if c < -2**31:
            return -2**31
        return c