x! - A Programming Problem
26 Nov 2009 16:00
This was originally posed to me sometime last year by a group who'd been given it in some test or another. It's quite a simple problem, with a reasonably simple solution, but it's still worth having a go (unless you've seen it before). Basically, you have to write function(s) which calculate n factorial in less than factorial time. The only arithmetic operation you may use is +. Solutions as a comment, or on a postcard of somewhere nice.
Good Luck!