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 hold integers within the 32-bit signed integer range. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

用的是Python 转换成str ,然后翻转，需要注意

1.翻转之后如果溢出，输出0

 class Solution:

     def reverse(self, x):

         """

         :type x: int

         :rtype: int

         """

         neg = x<0

         res = int(''.join(str(abs(x))[::-1]))

         if res > 2**31:

             res = 0

         if neg:

             res = -res

         return res