I was able to answer the question. Many did not, but the process was more about how you handled yourself through the process, how you communicated with the interviewer as you walked through the problem, than it was about reaching the actual solution. I know several people, bright people, that were hired there even though they never solved the puzzle.
After I got the proper solution, I asked the person that administered the quiz "Is this an indication of what kind of code gets written here?" He just started laughing and saying "no, no no". Because I would not take a job at any company that actually wrote code like that.
That interviewer ended up being my first manager, and we had a good work relationship. It was a great few years of my career.