Get it working first, then make it fast, then make it clean.

Finding the shortest path in an unweighted graph or tree level-order traversal.

Most DSA problems are variations of a few core patterns. If you recognize the pattern, the solution follows: When to Use It

A solution is only as good as its handling of the "weird stuff." Always test for: (null, empty strings, 0). Single elements (an array of size 1). Large inputs (integer overflows). Duplicates (especially in sorting or searching). The Golden Rule

Dealing with "Top K" elements or frequently updated minimums/maximums. 3. The "Rubber Duck" Debugging Technique