Ahhh, I remember my old college course on time complexity, which was effectively the professor picking on random kids and saying something like - "I have some 4 dimensional matrix multiplication algorithm which then uses a bloom filters to match on random ids... what is the time complexity of this?", and some poor kid would stutter something like, "aaaaahhhh.... O(nlogn)", only to have the professor to shout "No, wrong!" and go pick on someone else.