In the last contest, both tourist and ko_osaga copied the author's solution from the problem Matrix from Petrozavodsk Winter Camp 2013 Warsaw U contest: 123723552 and 123727448 respectively. You can easily verify that they didn't write this code themselves by looking at the comments in these solutions (written in Polish).
This is against the Codeforces rules. According to this post, we have the following rules:
Solutions and test generators can only use source code completely written by you, with the following two exceptions:
- the code was written and published/distributed before the start of the round,
- the code is generated using tools that were written and published/distributed before the start of the round.
Currently, the only reliable proof is the presence of code on the Internet and the presence of the used edition in the cache of well-known search engines.
For example, this rule accepts the use of the code from the website http://e-maxx.ru/ if the code was written and published/distributed before the start of the round. With the help of search engine caches, it can be easily shown that such code doesn't violate the rules. Similarly, it is permissible to use the code from a book/article that was published before the contest. On the other hand, using team reference code (for example, prepared for ACM-ICPC World Finals) is not allowed if there is no reliable and objective way to prove that the code was written before the contest.
This code is not available on the Internet publicly and was never published anywhere (at least I am not aware of that). There are two ways to get access to this code: either ask the author or have admin access to one of the contests where this problem is used. In my opinion, this falls into the second category (same as team reference code), as only a small number of people have access to this. Moreover, imagine if a similar issue would occur to some unknown, green or grey contestants. Their solutions for sure would be skipped. Please stop this elitism and ratism and treat all the contestants equally.
I am not saying that we should ban them or skip their solutions, but we should make sure that the rules are clear and fair and there are no exceptions. Maybe if you are using a third-party code, you need to add a comment mentioning the original source of the problem and this solution doesn't have to be widely available, but can be verified upon the request of someone investigating this potential cheating case? If that's the rule that we currently use, please add this to the aforementioned blog.