Programming performance/Apter K
Precise details are not known about how long it took to write this. Anecdotal evidence says 15 minutes, based on an e-mail conversation with an author's acquaintance.
See http://www.nsl.com/k/gspc/gspc.k as I do not have permission to copy the source code herein.
Note added by sa, the author of the original:
The original solution has been replaced by two contributions from the K mailing list.
No time estimates were given, but I'd expect something in the 10-30 minute range.