leetcode7. Reverse Integer

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:
---
Input: 123
Output: 321

Example 2:
---
Input: -123
Output: -321

Example 3:
---
Input: 120
Output: 21

Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−2^31,  2^31 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

class Solution:
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        if x >= 2**31 or x < -2**31:return 0
        if x > 0: flag = 1
        elif x < 0: flag = -1
        else: return 0
        
        x = abs(x)
        digits = []
        while x != 0:
            digits.append(str(x % 10))
            x //= 10
        
        out = int(''.join(digits))
        if out >= 2**31 or out < -2**31:
            return 0
        
        return out*flag