Questions from Facebook Puzzles, Project Euler, UVa, SPOJ, and the like do not expire, unlike Google Code Jam or TopCoder. Therefore, in order to be able to discuss such problems without ruining the challenge, we need some guidelines on how far we can discuss them.
This post is for discussing what these guidelines should be.
There are three reasons why I think Project Euler etc. questions shouldn't be posted here.
The first is copyright. The question submitter
... represents, warrants and agrees that it will not contribute any Subscriber Content that (a) infringes, violates or otherwise interferes with any copyright or trademark of another party ...
(StackExchange Terms of Service).
The second is that Project Euler strongly discourages people from seeking help elsewhere: the correct place to compare solutions to PE problems is in the forum which you unlock by submitting a correct answer. See Will Jagy's report of discussion with PE about questions posted on math.stackexchange.com.
The third is common courtesy. Ripping off other sites isn't nice.
I am of the opinion that if people cheat by Googling for help, then they're only hurting themselves. Sometimes though, I even myself give up on a challenging question and want to read up on the answer. Therefore I don't think we should be too restrictive. The one policy I think we might want to enforce is no full coded solutions, although we should still allow snippets which explain something like a DP solution easier than using mathematical notation would.
I don't think there should be a difference between puzzles that do expire and puzzles that don't expire. In the former case, posting a full solution ruins the contest for the participants, and in the latter it ruins the puzzle for the puzzlers. I don't think one is preferable to the other. I also don't think we ought to be the morality police; cheaters gunna cheat.
Some of the questions found on codegolf.com challenges are really great and I think worth replicating here. The advantage to this site oppose to codegolf is that all solutions are open so you can see the creativity of fellow golfers. I suppose the negative side is that it will allow for unscrupulous people to take advantage of this site and cheat at other competitions.
As Andy brought up there is another similar question which relates to competitions. I agree with the top answer that we should assist non-terminating contests with pseudo code. However, I think this question should directly relate to non-competition questions. I think this site is ultimately about having fun. The advantage of code-golf is that we can share our answers and learn from one another as code-golfers.
One last addition question. As it is possible that stackoverflow questions may be eventually be migrated, should we only allow non-stackoverflow questions?
Here are a few of the duplicates I found off hand:
CodeGolf.com:
Stackoverflow:
