Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0. Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
Input: x = 123 Output: 321
Input: x = -123 Output: -321
Input: x = 120 Output: 21
-231 <= x <= 231 - 1