Just read the lecture notes for a CS course that covers this already. It will almost always be a course that also covers the sorting algorithms and basic data structures(what is a linked list, tree, graph, etc.) It won't take that long. As for coming up with the Big-O omplexity for a routine on the spot, most job interveiws will throw something at you where it should be intuitive if you know the canonical algorithms. I have yet to read about someone having to solve a recurrence relation on the spot(everyone's already forgotten the cook book approach they learned in school, if they ever learned it at all). It's not a lot to remember, so no big deal if the only thing you use if for is to impress someone. If you want true "Who gives a shit?" material from academia, try Automata Theory, or whatever the course where you learn about the pumping lemma is called. Never read about that coming up in an interview.