Kattis is KTH's automated testing tool for programming exercises and tasks. Users submit code as their solutions to problems and receive instant feedback if it was correct or not.
We start out by finding a suitable problem. Then we write code to solve the problem in your favourite language (or some other language, if your favourite one is not supported by Kattis). After this, you submit the code to Kattis. Kattis will then compile your code and run it on some secret input. After some careful deliberation, you will get a judgement informing you whether your code behaved as expected or not.
More information can be found at: (www.open.kattis.com)[https://open.kattis.com/]