Meet the mascot
This cat has reviewed your code.
It is not impressed. It knocked your std::vector off the table on purpose.
Click the cat (or the button) for a fresh verdict.
What even is this?
We are a very serious organization with one goal: to find out whose C++ solution is the fastest.
Everyone who solves the task throws their program in the ring, and our
arena.sh turns the test run into a live game show with a leaderboard, commentary and a podium.
Correct answers earn points. Speed earns more points. A streak earns bragging rights. Wrong answers earn the cat's disappointment.
🌈 Visit the GitHub orgHow scoring works
Hall of Fame
| Contestant | Vibe | Points |
|---|---|---|
| definitely_not_O(n!).cpp | suspiciously fast | 9999 |
| copied_from_stackoverflow.cpp | "it works, don't touch it" | 8420 |
| vector<bool>_regrets.cpp | space-efficient, sanity-inefficient | 7001 |
| segfault_sally.cpp | lives fast, crashes faster | 69 |
| cout_debugging_enjoyer.cpp | forgot to remove the prints | 0 |
* Totally real results. Mostly. (Placeholder data, the real leaderboard lives in the arena.)
🏟️ PORNThe Rules™
- Do not delete or alter other people's programs.
- Only edit your own program.
- Do not change the tests or
arena.shwithout agreeing with the others. - Do not push anything that breaks the repo for everyone else.
- Play fair. It's for fun and learning (and mild cat-based intimidation).
🗓️ Events
Winter semester 2026/27, 2nd year Računalništvo in informatika, lectures only. Times and rooms are real. The descriptions are not to be quoted to professors.
Monday
P04
How To Monetize Your Side Project
Ekonomika in podjetništvo · 63248 · Tomaž Hovelja
Three hours on how companies make money. Useful if you'd like to be paid in more than exposure.
P19
Monday's Final Boss
Tehnične veščine · 63767B · Blaž Meden
One hour, straight after a three-hour block. Short on paper, long in practice.
Tuesday
P04
The Robots Do The Work Now
Procesna avtomatika · 63737 · Octavian Mihai Machidon
Process automation, starting at 08:00 on a Tuesday. The first thing worth automating is getting out of bed.
P01
Tiny Computers, Huge Responsibilities
Vgrajeni sistemi · 63738 · Patricio Bulić
Embedded systems: computers that run a washing machine and are not allowed to crash. Same slot as the course above, so you pick one.
P01
Where Do The Bits Live?
Organizacija računalniških sistemov · 63218 · Patricio Bulić
How a computer is actually put together, and what happens between your code and the electricity.
Wednesday
PA
Some Problems Are Simply Cursed
Izračunljivost in računska zahtevnost · 63283 · Uroš Čibej
Which problems can be solved at all, and how long it takes when they can. It eventually explains why your program is slow.
Thursday
PA
It Will Probably Be Fine
Verjetnost in statistika · 63213 · Aleksandar Jurišić
The course that puts a number on "probably". Thursday afternoon, three hours.
Friday
P01
The Reason This Org Exists
Algoritmi in podatkovne strukture 1 · 63279 · Tomaž Hočevar
This is where O(n log n) stops being a joke and the arena.sh benchmarks begin.
P01
A Spreadsheet Is Not A Database
Osnove podatkovnih baz · 63208 · Marko Bajec
Tables, keys and queries, in the last block of the week. You're free at 17:00 on a Friday.
Source: urnik.fri.uni-lj.si, group 2_BUN-RI, type P (lectures). A static copy from 24 Oct 2026, so check the official timetable for changes.
Links
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