CodeCup 2024 - An online programming competition  

CodeCup 2024 - An online programming competition

Welcome to CodeCup!

We offer you a challenging programming contest. Anybody can participate; there are no age restrictions or other special requirements. The CodeCup never charges entry fees.

In 2024 the game for the contest is Sudoku. We have placed a description of the rules online. You can always watch a sample game being played.


After you login in to the CodeCup system you can submit your program. You can find the submission section under "My submissions". Your submission will be tested automatically against our sample players to ensure that it follows the rules. After passing this check your program is ready to compete! Note that your program must be capable of playing both as first and second.

We will hold test competitions every three weeks starting in August. In these competitions you will see how your program performs against other players. You can follow the complete games and use this information to improve your strategy.

The next test competition has been scheduled for December 30th 2023.

Testing at home - Caia

The CodeCup Team enables you to test your program at home. Our testing software is free and enables you to organize competitions at home without involvement of other people. The software to play at home is called Caia. It works in the same way as our contest software. By hosting your own local competition you can test and improve your program in a fast and easy way. Download Caia and start today!


[update 30 Sep] Jelmer's Rule nr 1 has been implemented in the CodeCup system, and the Caia tarballs are updated to this new rule. The next competition of 7 October will use this new version, so please adopt your program to the new rule.

If you encounter any bug, please report it in the forum.

On September 20th, we have changed the rules of the CodeCup contest Sudoku. After a long, but good discussion in the forum, we decided to implement Jelmer's Rule nr 1. For the exact formulation of the rule have a look at the updated Rules webpage. The production of the new Caia tarballs needs a little more time and we hope to have them available one week before the next test competition. If all goes well, the next test competition of October 7th will be played with the new rules. Otherwise not. The old test competitions will not be removed. As soon as we have made new tarballs and updated the contest system, we will let you know via a news item and the forum.

I made the first test competition on 16 September visible again. It will be played with the original rules.

For the third test competition on 16 September we want to add an extra rule, so that the Sudoku competitions becomes more challenging. Read about this discussion in the Forum, the thread "Sudoku is heavenly skewed". Our suggestion is to add the rule that you can place two digits in the same move and must claim the uniqueness of the sudoku. The format will be like this: "Ab2Cd3!". This idea is from contestant Louis Verhaard. We ask you to respond to this idea in the Forum in the same thread whether this is a good idea or not. If so, we will adapt the checker/referee for this and will publish that the new rule is active. The new rule is consistent with the original rules, so all submissions will remain active. If we do add this rule, we will publish the activation of the new rule in the Forum and as a news article. If not, we will let you know too.

On July 15, 2023, we published the CodeCup game 2024 called Sudoku. Yes, it's the game you think it is. The only difference is that you start with a completely empty grid. You take turns placing digits on the grid and the moment you think you've made a unique sudoku with your last digit, you can claim its uniqueness and win. But only if you're right, otherwise you lose... It's no secret that a sudoku can be unique with only 17 digits on the grid. The question is how to work towards a small unique sudoku and win? We hope you like the challenge!