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Notebook

This folder is the short-reference layer of the repo.

Use it for:

  • notebook-ready snippets
  • formulas
  • checklist pages
  • contest-time reminders

It should stay denser and shorter than topics/.

Quick Split

  • Notebook = recall the main invariant, signal, or trap fast
  • Template Library = retrieve the smallest reusable snippet fast
  • Build Kit = route between notebook, templates, and workflow pages

Contract

This layer answers one question:

I already mostly know the area. What is the shortest route back to the right invariant, trap, and reusable snippet?

Every mature cheatsheet should bias toward:

  • Use when
  • Do not use when
  • Choose by signal
  • one or two core invariants
  • one or two main traps
  • direct jumps to topic pages, templates, and repo notes

It should not try to reteach the full topic. If you need proofs or slower walkthroughs, jump back to topics/.

Use This Layer When

  • the area is mostly known, but retrieval feels slow
  • you want the lightest viable template family quickly
  • you need the main invariant or failure mode under contest pressure
  • you want one nearby repo note to reopen, not a long tutorial

Do Not Use This Layer When

  • you are learning the topic for the first time
  • you still do not know the brute-force baseline
  • you cannot yet explain why the main technique works
  • the problem needs a slower decision page more than a compact reminder

Fast Retrieval Loop

When you are mid-problem and want the shortest route back to something reusable:

  1. open the relevant cheatsheet for the family
  2. pick a template or invariant from there
  3. jump back into the topic page only if you need proof, pitfalls, or a slower explanation

This is meant to be the layer you skim during implementation, not the layer you study first.

Sheet Contract In Practice

The shortest useful scan order is:

  1. Use when
  2. Do not use when
  3. Choose by signal
  4. Invariant / trap
  5. one template or repo anchor

Representative Anchors

Current Sheets

Good Pairings

Learn -> Practice -> Retrieve

Use this layer as the Retrieve step, not the first step:

If you need... Open first Then
proof or slower explanation Topics come back here after the idea is trusted
a concrete next problem Problem Finder then reopen the relevant sheet
a pasteable snippet Build Kit then the relevant template

Reopen Rules

  • if you need proofs, go to topics/
  • if you need a pasteable skeleton, go to Template library
  • if you need the exact next problem or next short set, go to Problem Finder