Er... is it just me, or is this a terrible interview question? Assuming no external storage, I can imagine spending a few hours working out this problem for fun

Er... is it just me, or is this a terrible interview question? Assuming no external storage, I can imagine spending a few hours working out this problem for fun, but to do it in 45 minutes on a whiteboard seems exceptionally difficult if you're not familiar with it already. (Or is this one of those "let's talk it through, you don't need to arrive at a perfect answer" deals?) I could be wrong. Maybe I should just sit down and try it, but timed problems stress me out in general, even if nothing's at stake.