The Pattern Map
Almost every coding problem is a known pattern wearing a costume. The meta-skill — the thing interviews actually test — is stripping off the costume to see the shape underneath. This page is the decision guide for doing exactly that, plus a drill that forces you to recognize patterns instead of being told which one to use.
Bookmark it. It’s the single best thing to re-read the morning of an interview.
”If you see this, reach for that”
The clue is almost always in the problem’s constraints and verbs, not its story. “Contiguous subarray” → sliding window. “All possible…” → backtracking. “Minimum X such that…” → binary-search-on-the-answer or DP. “Already sorted” → two pointers or binary search. Underline those phrases first — they’re the seams of the costume.
Drill: name the pattern
Reading the map is passive. This is active: you get a problem with the technique hidden, and you have to decide the approach yourself before revealing it. That decision — under mild uncertainty — is the muscle the interview works.
Interleaving is uncomfortable on purpose. Practicing 20 sliding-window problems in a row feels productive but teaches you almost nothing about recognizing sliding window — you already know that’s the day’s topic. Mixing problem types (like this drill, and like a real interview) is harder and slower, and that “desirable difficulty” is precisely why it sticks. If it feels easy, you’re not learning.
Go deeper
- Full complexity tables and templates → Cheat Sheet
- Concepts you’ve missed resurface on a schedule → Review Queue
- Not sure where to start → Find Your Starting Point
- The complete curriculum → the 30-day roadmap