kJudge : Local Judge CLI for CodeForces

Revision en4, by kilobyte136, 2026-04-14 13:16:18

Hey Codeforces,

During contests, I kept losing time on things that had nothing to do with solving the problem — manually copying samples into an online compiler, re-running after every edit, squinting at wrong answer output trying to spot the difference. It's friction that adds up, especially under time pressure.

So I built kJudge, a CLI tool for local testing of CF solutions. The core idea: fetch samples automatically, watch your file for changes, and show you a clean diff when your output doesn't match. No browser tab switching, no manual input pasting.

What it does:

  • Auto-fetches samples from Codeforces for any problem — just point it at the problem URL
  • Watch mode — re-runs your solution on every file save, so the feedback loop is as tight as possible
  • WA diffs — expected vs actual output shown side by side, not just "wrong answer on test 2"
  • Contest scaffolding — one command sets up folders and templates for every problem in a round
  • Works with C++, Python, and Java; pure CLI so it's IDE and OS agnostic

Setup is a single binary download from Releases — run it once and it adds itself to PATH. Full guide in the docs.

preview

Repo: https://github.com/Byte-ne/kJudge Docs: https://byte-ne.github.io/kJudge

This is my first public tool — built it for my own practice sessions and figured it might be useful for others in the same boat. If something's broken or you want a feature, open an issue or drop a comment.

Tags cli, command line tool, open source, cpp, beginner, tools

History

 
 
 
 
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  Rev. Lang. By When Δ Comment
en4 English kilobyte136 2026-04-14 13:16:18 1336
en3 English kilobyte136 2026-04-12 19:46:55 1447 Tiny change: ' a simple implement' -> ' a simple string & implement'
en2 English kilobyte136 2026-04-11 11:07:05 2 Tiny change: 'deforces, I am kilob' -> 'deforces, \nI am kilob'
en1 English kilobyte136 2026-04-11 11:06:40 1401 Initial revision (published)