Spiral Matrix
Recognize the pattern
Brute force idea
A straightforward first read of Spiral Matrix is this: No simpler alternative — spiral traversal IS the approach. 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
The real unlock in Spiral Matrix comes when you notice this: Track four boundaries (top, bottom, left, right), shrink inward after each pass. Instead of recomputing the world every time, you preserve just enough context to let the next decision become obvious.
Key invariant
The compass for Spiral Matrix is this: Process one full ring (top row → right column → bottom row → left column), then shrink. As long as that statement keeps holding, you can trust the steps built on top of it.
Watch out for
One easy way to drift off course in Spiral Matrix is this: Not checking if the boundary has collapsed after each direction — causes duplicate elements. The fix is usually to return to the meaning of each move, not just the steps themselves.