There are some examples that there are similar problems in math contests (I can't distinguish if it's deliberately copied from math contests or just a coincidence).
317E Princess and Her Shadow, which is almost the same as a problem from Canadian National Olympiad link
618F Double Knapsack, see the discussion here
1684H Hard Cut, see the discussion here
K in Yuhao Du Contest 5. Yes, I admit the idea is from a problem in All-Russian MO link
Sometimes authors just learn the idea from MO problems. But sometimes, the problem is just identical (like 1684H).
I don't think there is much difference between copying problems from math contests and copying problems from an old opencup contest. However, the community seems much more tolerable of copying problems from math contests.
Maybe the difference is that the opencup problems are known to more participants. So copying problems from math contests has less impact.
Some updates:
For all problems mentioned above, solutions are almost the same as MO problems they correspond to.
The following are more examples that share the same setting with MO problems, but the solutions are not very similar. I feel these problems are ok.
HDU 4660, commented by MinakoKojima. It shares the same setting with IMO 2011, Q2. But this problem is asking different things.
I in Yuhao Du Contest 7. It shares the same setting with IMOSL 2009, C5. But it's much harder than that IMOSL problem. So I feel knowing this IMOSL problem doesn't help.
A Chinese problem. It's definitely inspired by RMM 2019 Q3. And they share a similar idea. But I feel it's not bad since there are still several steps (however, basically implementation issues) to make the proof in the RMM problem work in this problem.
D in Tianjin 2012. And this problem also happens in a recent Chinese team training contest. As far as I remember, there is a similar IMO problem in the 1990s. But I didn't remember the exact source.
At least it's better than taking questions from a physics competition or academic paper... The result depends on what part of the original question you have learned and extracted. Here is a positive example.
Personally, I think the above problem is pretty nice.
I think both copying from IMO or Opencup is cheating. It's just the difference of how many people can see the copied question and copy the solution.
UPD: Why did I get so many downvotes? Is there anything I said wrong?
If you clearly tell where you copied the problem, or where you were inspired at, then the organizer will decide. I guess it will be rejected from CF, though I'm not an organizer.
Btw I frequently copy problems from academic papers.... uhoh
I think you should let the authors of those CF problems speak for themselves, obviously there have been problems copied from math olympiads but the first 3 examples you pointed out don't seem to be that.
Okay, I change some words in the post. But personally, I feel the first and third examples are more likely to be inspired by MO problems.
Auto comment: topic has been updated by jqdai0815 (previous revision, new revision, compare).
In 2019, the ICPC Pacific Northwest Regional had a problem (problem H) which also considered the same process as IMO 2011 Problem 2.
The Discord server where we discussed the viability of the problem has since been deleted by the admin so I do not think I can dig up our conversations regarding whether this problem was viable. We ultimately decided to use this problem, we didn't believe knowledge of the IMO problem was meaningful to the problem we proposed. I'll let the community decide if this problem is reasonable to propose given the shared underlying process, perhaps taking into consideration that it was for an offline ICPC regional.
I personally think that the optics of such a problem are nonideal, irrespective of how well-known the underlying problem is. I do feel that a lot of problem ideas tend to be inspired from other problems so it is difficult to draw a line here, but problems which are meaningfully different feel like they should be fair to propose.
I don't mind if a programming contest problem reuses an idea from a math contest problem if it builds upon it in some way. Some of the examples meet this bar while others don't. In cases where a math contest problem was reused, it seems like there weren't any earth-shattering effects on the standings like what happened in round 810.
Here's a few more examples to add:
We shouldn't assume by default that people copy other problems intentionally. With so many problems existing, it's natural for some ideas to be rediscovered. A funny example is ARC136C = HMMT February 2022 Team/8. It just so happens that HMMT happened before ARC136 yet the problems were posted after ARC136, so the problem was independently made twice.
Also, the in the original post, the IMO problem that you're looking from that is similar to the Tianjin problem is probably IMO 1986/3.
Another example of high similarity: 840A - Leha and Function — IMO 1981/2
The 2019 ICPC Vietnam National Contest Problem I is a direct extension of IMO 2019 P5, and the ICPC problem even quoted "IMO 2019 Problems".
The discussion to solve that particular extension can be easily found online.
I am interested in the organizer's decision during that time, given that the ICPC was hosted only ~4 months after the IMO. Personally, for this case, I think this can give an unnecessary advantages to some people who closely follow the IMO community. IMO being a very well-known contest and for it to be quite recent does not help to justify that problem to be used either.
But in general, extracting, reusing, and extending ideas from existing problems is totally fine, as long as the organizer is aware of where the problems you are inspired from. I understand that inventing a novel problem is getting harder and harder nowadays, and the chances that your idea has appeared elsewhere can be very high.
In the end, you and your organizer should decide together whether it is wise for your problems to be used based on your own conscience and moral reasoning.
2020 ICPC Vietnam National Contest Problem C is also the same as IMO 2020 P4, hosted under 2 months after the IMO.
my opinion in short: it must happen more often.
I stand with learning MO ideas or even using original MO problems under the following 2 restrictions:
it is used on the onsite competition or under the offline environment or just for exercises, i am glad to see them appeared on gym or some other practicing platform but not in a rated div.1;
the problem should be related with multi computation, which means it should not only rely an O(1) formulation, i think the difference between our information games and MO is whether using computer to speed up solving problems.
BTW, i don't like math problems (since i am not good at it), but i think some of these problems really inspire our contest.
i dont have fun from any problems anymore
if the problem is directly copied from other source we should attribute/give credit to the original author of the problem.
(i don't know why you guys are down-voting, have i said something wrong? if so please explain before down-voting. i will be very thankful)
m_m