Reverse Number

Given an integer, reverse its digits. For example, 1234 becomes 4321, and -1234 becomes -4321. Note: If the reversed number would overflow a 32-bit integer range $[-2^{31}, 2^{31}-1]$, return 0.

Reversing digits mathematically uses the modular operator to extract the last digit and integer division to remove it: $\text{last\_digit} = n \bmod 10$, then $n = \lfloor n / 10 \rfloor$. The extracted digit is appended to the reversed number by shifting left: $\text{result} = \text{result} \times 10 + \text{last\_digit}$.

1. Handle the sign: store is_negative = n < 0 and work with abs(n).
2. While n > 0, extract the last digit via n % 10 and append to result via result = result * 10 + digit.
3. Remove the last digit with n = n // 10.
4. After the loop, reapply the sign if needed.
5. Check overflow: if the result is outside $[-2^{31}, 2^{31}-1]$, return 0.

• Using Python string conversion (str(n)[::-1]) — correct but doesn't handle the overflow check naturally
• Not preserving the sign: using abs() but forgetting to reapply negative sign
• Integer overflow: Python has unlimited integers, so you must manually check the 32-bit bounds

This problem teaches digit-by-digit decomposition using modulo and integer division — a pattern that reappears in Armstrong number checks, palindrome number checks, and digit sum calculations.