Looking at http://stackoverflow.com/faq I see the requirement that, You should only ask practical, answerable questions based on actual problems that you face. There is no way that the question fits that criteria.

I've had personal interaction with moderators over that exact issue. I personally enjoyed answering algorithm questions. However it came to my attention that any time moderators notice that type of question, they close them for exactly that reason. (No matter what the wishes of people who ask and answer that type of question might be.)

As for the historical accident - I agree. I'm amazed that an answer given years after the question was asked got as much attention as it did.