I got to mark an assignment at uni that I'd also done. There seemed to be just three different versions that were "obviously" copied... then I saw one identical

I got to mark an assignment at uni that I'd also done. There seemed to be just three different versions that were "obviously" copied... then I saw one identical with mine! With just wminor differences. I hadn't copied, and I couldn't see how they could have copied mine. On reflection, there is much convention in code (this was c IIRC), loops, indices and cordinates variables are standard. And, each level of a problem only has a few obvious ways to approach it. The same underlying algorithm - especially in a uni course about algorithms - also tends to suggest particular designs. The eye of an octopus is striking similar to the human eye. Does that mean they are related, other than by objective?