The most expensive mistakes
Most interview misses come from process breakdown, not missing one obscure trick.
Top mistakes and fixes
| Mistake | Why it hurts | Fix |
|---|---|---|
| Coding too early | Misses constraints and edge cases | Ask 2-3 clarify questions first |
| No explicit plan | Leads to mid-code rewrites | State pattern + complexity before coding |
| Silent coding | Interviewer can't assess your thinking | Narrate intent at each step |
| Weak testing pass | Off-by-one bugs survive | Run tiny edge-case checklist at end |
Debugging mistakes under pressure
- Random edits without hypothesis
- Ignoring failing test details
- Re-running without tracing
Use a strict sequence: reproduce -> isolate -> patch -> verify.
Communication mistakes
- Saying only final answer
- Not explaining trade-offs
- Hiding uncertainty
A better line: "I can do O(n log n) by sorting; if we must do O(n), I'll switch to a hash map approach."
FAQ
What should I optimize first: speed or correctness?
Correctness and communication first. Speed improves naturally with repetitions.
How do I recover if I get stuck mid-interview?
State where you’re stuck, propose one hypothesis, and test with a tiny example.