I had him as a teaching assistant when I was teaching data structures at Princeton back in Fall 2013. Princeton CS has their professors rotate through as TAs ev

I had him as a teaching assistant when I was teaching data structures at Princeton back in Fall 2013. Princeton CS has their professors rotate through as TAs every so often through their courses. That semester, I made a slight mistake on the final exam where I asked students to create an algorithm that could find the second shortest path from s to every other vertex in a graph. I forgot to specify that the second shortest path should be simple (i.e. should not reuse any vertex twice). Having to deal with non-simple paths makes the problem much much harder. None of the students figured it out in the time available, and I'm sure I would also have been stumped if I had tried to solve the problem. Bob figured it out though. And then I remember he graded all 150 solutions to the problem himself, having as a blast as he went through students attempts at an effectively impossible problem.