The Bundeswettbewerb Informatik is a German government-sponsored computer science challenge, "aiming to arouse young people's interest in informatics and to encourage them to become more actively involved with the content and methods, as well as the future perspectives, of informatics applications".
It is organised annually, and consists of three different rounds. I participated twice in the first round, and once in the second, and you can download my submissions here. Executable are not always available - you'll have to compile yourself where they're missing, sorry.