Reverse Integer
Recognize the pattern
Brute force idea
A straightforward first read of Reverse Integer is this: Convert to string, reverse, convert back — works but misses overflow. That instinct is useful because it follows the prompt literally, but it usually keeps revisiting work the problem is begging you to organize.
Better approach
A calmer way to see Reverse Integer is this: Extract digits with modulo, build reversed number — digits. The goal is not to be clever for its own sake, but to remember the one relationship that keeps the solution grounded as you move forward.
Key invariant
The truth you want to protect throughout Reverse Integer is this: result = result * 10 + lastDigit, where lastDigit = x % 10. If that remains true after every update, the rest of the reasoning has a stable place to stand.
Watch out for
One easy way to drift off course in Reverse Integer is this: Integer overflow — check before multiplying by 10 if result would exceed 32-bit int range. The fix is usually to return to the meaning of each move, not just the steps themselves.