Just in case you didn't know already, we have a fairly new type of challenge:

I enjoy these challenges very much, but I don't know if the current format (cops post answers, robbers post comments) is optimal.

I see the following problems, in descending order of importance:

  1. Comments are limited to 600 characters and have very poor formatting, so a robber has no convenient way of explaining how he killed the cop broke the submission.

  2. New users cannot post comments, since they'd need 50 reputation for that. Newbie robbers have no choice but to post answers instead of comments (exhibit A, exhibit B) or just skip the challenge altogether.

  3. The question has to be cluttered with two leaderboards. The comment sections are a mess.

  4. Only cops can earn reputation from upvotes. There's no green checkmark for the best robber.

So, should we

  • …create separate challenges (one for cops, one for robbers) and keep things nice and separate?

  • …let robbers post answers as well? This solves 1, 2 and 4, but the clutter would be even worse.

  • …let robbers edit answers, as this challenge did?

  • …leave things as the are?
  • 14
    \$\begingroup\$ "Where should we put robbers?" In jail, obviously. :P \$\endgroup\$
    – Alex A.
    Aug 12, 2015 at 20:18
  • 2
    \$\begingroup\$ @AlexA. that comment was underappreciated, IMO \$\endgroup\$
    – cat
    Dec 26, 2015 at 23:46

1 Answer 1


Create separate challenges

I'm not saying this is the solution, but we've just talked about this in chat, and I wanted to make a meta post for this anyway. So this answer will act as a collection of pros and cons of this solution and comments and votes will certainly show the communities opinion (please add similar answers for the other options).

This really solves all the problems:

  1. Full-fledged answers with formatting and everything for the robbers.
  2. New users can answer.
  3. Separate questions for separate leaderboards. Note that the OP would still have to maintain both of them, because answers to the robbers' challenge can invalidate/crack answers from the cops' challenge.
  4. Robbers get upvotes and the best robber gets accepted. In fact, we could offer bounties for cracking very hard cop submissions.

It has one problem though: the robbers' challenge cannot be answered when there are no uncracked cop submissions. I don't know how much of a problem that is, but it should be kept in mind.

Another thing I want to mention in this context: the four existing challenges were all of the format that every cop submission had to be cracked individually. In theory, this tag could include somewhat different challenges though.

The model challenge for this is this sandbox proposal. In short, the cops write maze generators and the robbers write maze solvers. Now there's no one-robber-cracks-one-cop-answer system any more. It's more like an asymmetric . This would be ideal for posting separate questions! In this case, solvers can be written before any generators exist (even though they can't be scored yet). And cops (generators) will never be invalidated, they also just get a score, depending on how well the robbers (solvers) perform, which means once the first generator exists an arbitrary amount of robbers can participate.

So even if we decide that this model doesn't work for the type of cops-and-robbers challenges we had so far, there are certainly types where we should definitely do this. Whether the problem mentioned above is too critical to always apply this, is something I'm happy to discuss in the comments.

  • 2
    \$\begingroup\$ While I agree this would be ideal for your example challenge (maze gen/solve), I don't think it's a good fit for the current one-to-one cops and robbers challenges. \$\endgroup\$
    – Geobits
    Oct 16, 2014 at 21:30
  • 2
    \$\begingroup\$ Also, someone needs to polish/post that maze challenge. I've had most of an architect built for months now ;) \$\endgroup\$
    – Geobits
    Oct 16, 2014 at 21:31
  • \$\begingroup\$ The robbers still have to comment or edit to mark them invalidated. So in most cases, the robbers' challenge has almost nothing worth reading for other users. \$\endgroup\$
    – jimmy23013
    Oct 16, 2014 at 23:03
  • \$\begingroup\$ @user23013 That depends on the type of challenge. In many-vs-many challenges like the maze gen/solve example, their submissions would be programs just as full-fledged as the cops' ones. In one-vs-one challenges like the regex golf, the robbers' answers could still elaborate on how they solved it, what other valid keys would look like and in case they used computational methods to crack the key, they could also include the relevant code. And of course, if the challenge is split, then it's the challenge host's responsibility to keep track of cracked submissions. \$\endgroup\$ Oct 16, 2014 at 23:09

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