I don't think you can; in my experience that's a feature of various code-golfing sites, as seeing others' solutions would give you a rather unfair advantage.

Past Perl golfing contests often (always?) had a deadline after which solutions would be revealed and a post-mortem prepared so everyone could compare their solutions, learn, and improve on them still. (I remember a very nice and rather huge PDF collecting all these, from various contests/sites.) Unfortunately this appears to have fallen out of style.

AppleFritter is right - there's no such option.
You have to write your own code, not shorten other ones. If there was an option to view codes after the deadline, problems would have to be added constantly.

For that, you can visit Anarchy Golf.
More problems, more languages, more users. And there are 2 types of problems: endless and post mortem. From what I understand, you'd be more interested in post mortem ones.

Sorry for such late answer but I wasn't notified.