revise in minutes
Cheatsheets
Not one long page: one short sheet for each moment of a coding round. Find the moment you're in, open its sheet.
Before you code
You've just read the problem. Decide how fast, which pattern, which structure.
- How fast must it be?Use it when: You've read the constraints (n ≤ …) and want to know which complexity will pass.the n → Big-O ladder and how to use it · 2 min
- Which pattern is this?Use it when: You've read the problem and don't know where to start.signals → pattern, grouped by family · 8 min
- Which data structure?Use it when: You know what must be fast (lookup, min, order, undo…) and need the right container."I need…" → what to use, with its cost · 4 min
While you code
You know the plan. Get the Java right without guessing.
- Java API by collectionUse it when: You're coding and forgot a method name, or what it costs.every call used in the course, by collection · 6 min
- Pattern templatesUse it when: You know the pattern and want its skeleton: the loop, the invariant, the usual bugs.verified Java skeletons, one per pattern · 3 min
- Java trapsUse it when: Before you press Submit, or when the output looks impossible.the Java gotchas that fail hidden tests, one fix each · 4 min
After you code
Check it, explain its cost, and get ready for the follow-up.
- Big-O of everythingUse it when: The interviewer asks "what's the complexity?", or you're comparing two approaches.cost of every Java operation, then each chapter's tables · 6 min
- Edge cases to testUse it when: Your code works on the example. Now break it before the interviewer does.tick-lists by input type · 3 min
- The night beforeUse it when: Your interview is tomorrow. One calm page, then sleep.triggers, budget, top traps, the 45-minute plan · 10 min