I suspect that one of my students has downloaded his solution from the Internet as it is a very common basic task. The assignment was to write merging of sorted sequences into a single sorted sequence in C++. I would like to find the source of the plagiarism. (Just to be clear: comparing solutions inside the group is easy, that is not the task here.)
My daydream is that I paste the source code into some textarea, press the "Search" button and it displays similar source codes on the Internet. Is there any site like that?
Sounds something like what turnitin.com is meant to do. The site is intended to catch plagiarism in english, but you could read up and see what it can do for you.