So here’s a puzzler for today:  How can you numerically simulate two planets interacting via gravity, in a universe with infinite volume?  Of course you only have standard computing architecture available.  Once you have a guess, make gravity repulsive and see if your solution still works.

And since I’m totally an evil T.A., discuss when and how your numerical error grows “too large”.  Good hunting!

But you, my avid reader, protest “it’s a test to see how you think and reason”. Okay that’s fair, but I, for the sake of discussion, claim quicksort and other standard algorithms aren’t the right way to test an applicant’s reasoning ability. All applicants know quicksort could be asked, so we all look it up. Now, when we are sitting down during an interview, we’re trying to recall all the intricacies of a mature algorithm. Instead of reasoning through divide-and-conquer, I’m thinking “oh crap, now how to I pick the pivot to avoid those QS-attacks?”. I’m trying to remember how to get all the details right, when I should be iteratively addressing problems as they arrive.

Of course, if you’re hiring someone to squeeze out the next 1% of execution time in some DB-query, then absolutely he or she should know every damn intricacy of the standard algorithms. But for the rest of us, I think non-standard brain teasers or puzzles seem much better than reproducing a well-known mature algorithm.

IMHO =)

XKCD always getting to the heart of the matter