My solution, performs all the extra credits. http://members.iinet.net.au/~removed_email_address... tate.rb It's basically: get a stack of 2d arrays, chop them in half, rotate them around and plonk them on top. The key bit was probably figuring out that you could just rotate the entire piece of paper, fold one way and then rotate it back, so you don't have to deal with the headaches of figuring out how each fold will mutate the arrays. I also added in an optimisation to keep track of the previous rotation so I didn't have to burn cycles constantly rotating it back to the original orientation. Once I was done I sat down and wrote out each fold individually, but it ended up being slower than rotate and fold (I eventually optimised it to be slightly faster, but I preferred the simpler code of the rotate method). Unfolding wasn't very hard either, once you'd had a look at some stacks just prior to the last fold. If there was a difference of one between one of the rows on either side it was a left or right fold, otherwise it was a top or bottom fold (depending on which layer had the higher numbers). Did the same rotation magic to prevent headaches on figuring out the unfolding algorithyms.
on 2006-01-24 07:29