Write reverse_number(n) that returns the integer whose digits are those of n in reverse order. Leading zeros disappear naturally because the result is an integer. Use arithmetic and a loop, not string slicing.
Examples
Input: n = 1230
Output: 321
Input: n = 45
Output: 54
Constraints
0 <= n <= 10**18
Goals
- Extract the last digit with % 10
- Build a new number digit by digit