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Practice

Deliberate repetition, not random grinding

Practice is organized by topic first, not only by judge. The goal is to help you learn an idea, solve targeted problems, and come back for repetition without losing the connection between concept and use.

Open ladders Open problem finder Mixed rounds (later) Contest playbooks (later)
Topic-first Judge-linked Review-friendly Contest-aware

Choose A Practice Mode

  • Ladders

    Stay inside one topic long enough to build recognition and clean execution.

    Open ladders

  • Problem Finder

    Use one searchable doorway when you know the weak topic, want the next good set quickly, or need a resume / review / fresh follow-up queue.

    Open problem finder

  • Mixed Rounds

    Mix areas on purpose when you want retrieval practice, breadth, and contest-style switching. The starter packs are best after you already have one pass through the corresponding ladders.

    Open mixed rounds

  • Contest Playbooks

    Train toward a contest style such as Codeforces, ICPC, USACO, or olympiad-style prep with clearer workflow guidance.

    Open contest playbooks

The Default Practice Loop

Use the repo layers in this order whenever possible:

  1. learn the idea in topics/
  2. stay in one family through Ladders
  3. compare against one solved note
  4. reopen Notebook or Build Kit only if retrieval or implementation is the bottleneck
  5. move to Mixed Rounds or Contest Playbooks only after the family is already familiar

That is the default topic -> ladder -> note -> retrieve -> switch loop of the repo.

Session Shapes

Use one of these when you want the repo to feel like a training system, not a library shelf.

Session shape Start with Best follow-through
Resume queue Problem Finder with Resume attempted reopen the topic only if recognition is shaky, then finish the note
Review queue Problem Finder with Review solved one repo note, then one fresh external rep
Fresh external reps Problem Finder with Fresh external or Core external set reopen the corresponding topic map or ladder only if the new rep exposes drift
Codeforces short round Contest Playbooks via Codeforces Codeforces Short Round 01, then Codeforces Upsolve Worksheet
Switch drill Mixed Rounds Notebook or Build Kit only after the round shows a real gap
Track-specific block Contest Playbooks return to Problem Finder for the next concrete queue

Choose By Bottleneck

If your bottleneck is... Best first door Then
I need the next good problems Problem Finder the corresponding ladder or playbook
I need a clean resume or review queue Problem Finder the corresponding note, ladder, or mixed round
I want Codeforces-style short-round shipping or anti-hack practice Codeforces Codeforces Short Round 01 or Anti-Hack Workflow
I am still learning one topic the corresponding topic page in topics/ Ladders
I know several topics but switch badly Mixed Rounds Notebook
I care about one contest format now Contest Playbooks Problem Finder

How To Use Problem Notes

  • Read the recognition cue first

    Check the topic, subtype, and recognition sentence before reading the solution. That keeps your practice tied to pattern recognition instead of only code recall.

  • Compare the transformation, not just the answer

    Ask what changed between the raw statement and the reusable topic pattern. That delta is usually what you want to remember for the next problem.

  • Track status honestly

    Keep todo, attempted, solved, and reviewed meaningful so the repo becomes a real training log.

Browse The Catalog

  • Problem index: one table for every currently tracked solved note, with links to the note, code, ladder, and tutorial hub
  • External problem index: curated official and trusted problems outside the repo, organized by topic and usable as the next practice queue
  • Topic maps: source-backed pages for each subtopic, including learning references, exact practice sources, follow-up reading, and every repo problem tagged there

After One Practice Session

  • weak topic recognition -> reopen the corresponding tutorial in Topics
  • weak family-level repetition -> stay inside Ladders for one more note set
  • weak implementation trust -> reopen Build Kit
  • weak retrieval under pressure -> reopen Notebook
  • weak contest-time behavior -> reopen Contest Playbooks
  • weak Codeforces short-round shipping or hack discipline -> reopen Codeforces and Anti-Hack Workflow

Path Shapes

practice/ladders/<area>/<subtopic>/<problem-code>.md
practice/mixed-rounds/<pack>.md
practice/contest-playbooks/<track>.md

Contributor note contract lives here:

Best way to use this section

Read one topic page, pause at Recognition Cue, solve or re-solve the problem, then compare your transformation against the stored note before reading the code.

Current Examples

Data Structures

Graphs

DP / Greedy

Math / Combinatorics

Geometry

Advanced / Constructive