This week, the Central European Olympiad in Informatics 2023 (CEOI 2023) is going to take place! CEOI is a programming contest for secondary school students from countries in Central Europe. Around 50 contestants from Croatia, the Czech Republic, Germany, Hungary, Poland, Romania, Slovakia, Slovenia, and our guest countries Israel, Switzerland, and Ukraine will compete against each other, solving difficult problems of algorithmic nature. Each participating country sends 4 contestants from their national olympiads which take place in the months beforehand.

The contest consists of two days, Tuesday and Thursday, on each of which the contestants have 5 hours to solve 3 problems of varying difficulty. Each problem is worth 100 points that are distributed into multiple subtasks with different constraints that allow the participants to earn partial scores.

CEOI 2023 is hosted in Magdeburg, state capital of Saxony-Anhalt and among the most historical cities of Germany. There will be a live scoreboard during the two competition days, and we will host an online mirror around a week after CEOI. For more information about the contest, visit the official website at ceoi2023.de.

We wish all CEOI contestants an enjoyable contest and a good time in Magdeburg!

-- CEOI 2023 committee

Update: The first competition day has just started. The scoreboard can be found here.

Update: The contestants are right now competiting in the second contest. As before, the scoreboard can be found here.

Update: CEOI 2023 has just concluded. With the medals awarded in the closing ceremony yesterday (see here for the final ranking), the teams are now on their way back home. We hope that everyone enjoyed the contests. Congratulations again to all participants, all medalists, and in particular to the overall winner of CEOI 2023, lucaperju!

Also, we are happy to invite you to participate in the online mirror of CEOI 2023 on Friday, August 25, 2023 at 7:00 UTC and Saturday, August 26, 2023 at 7:00 UTC! The mirror will be held on CMS which was also used for the official contest. We will open the registration closer to the start of the mirror.

Update: The online mirror is now configured! Since this was requested, the mirror will now have a longer timeframe during which you can participate: for both contests, you can pick an arbitrary 5 hour timeslot between Wednesday, August 23, 2023 at 0:00 UTC and Sunday, August 27, 2023 at 23:59 UTC to participate. Note that the mirror will not be permanently monitored. Also, please refrain from discussing the tasks publicly until Monday so that everyone can enjoy the mirror without knowing the tasks in advance.

To register for the contests, go to the contest system, select the contest that you want to participate in, and register an account (it's not necessary to enter an email). If you want to participate in both contests, you afterwards have to go to the other contest, click on the registration link and enter your account details in the "Join contest" tab. Then, starting from Wednesday, when you log into the system you can start your 5 hour timeslot whenever you want.

Final Update: As the online mirror nears its end, we hope that you have enjoyed the problems, or that you still will if you plan to use the last few hours to take part. Once the contests are over, there will be an analysis mode for about a week for both contests where you can analyse your solutions and try to improve them. We will also upload the problems, the test data, and some spoilers for all problems to the official website in the near future.

With this we say goodbye and look forward to CEOI 2024 in the Czech Republic!