Description
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.