Reverse Integer

Assume the environment does not allow you to store 64-bit integers (signed or unsigned).

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 [-2147483648, 2147483647], then return 0.

Input: x = 123
Output: 321
Input: x = -123
Output: -321
Input: x = 120
Output: 21
Input: x = 0
Output: 0

problem 7: https://leetcode.com/problems/reverse-integer/