I participated in ABC 250 last night, and there is something really makes me sad.
I didn't solve the problem G and problem Ex, but after the contest someone told me these two problems are exactly the same as two previous problems on Codeforces.
Let's compare:
And recently I often hear others talking about ABC that has a lot of problems are exactly the same as some old problems on Codeforces or other platforms.
Is this normal and fair enough? I know the meaning of ABC may be more educational, but it's still quite sad to hear someone say some words like ‘I find the same problem on Codeforces and got AC by learning the solution during the contest’ .
Sorry for bothering.
As a real beginner, I think it's very difficult to practice problems with 2000+ ratings like 1253F or 865D. Even I have never challenged these problems (or similar).
May feel unfair sometimes, but "Have you practiced this kind of problems?" I think it's okay to give a problem with a focus on.
I'm worried that ABC will become AtCoder Back-problems Contest. (just a joke)
Some other problems in ABC — similar problems appeared in other platforms (maybe some in Chinese, use translate software then):
ABC248G — CF990G (Share the same trick, but not exactly the same. The one in ABC is a bit harder.)
ABC246G — Luogu P3554 (Almost the same. Just change a bit.)
ABC242F — Luogu P3158 (The one in ABC is weaker. The original problem can choose to 10 colors.)
ABC241G — UVA1306 (Share the same trick, but not exactly the same. The one in ABC is a bit harder.)
ABC239G — Luogu P4662 (Almost the same.)
ABC238G — Luogu P5071 (Both of the problems can be solved in Mo's algorithm. In this case, the ABC one is weaker.)
ABC237G — Luogu P2824 (Almost the same. Share the same trick.)
ABC236G — Luogu P2886 (Almost the same.)
All in all, most of ABC rounds is really nice and educational. Hope ABC will be better in the future.
It's because that the problems in ABC are often very 'classical', and as we all know,classical problems have more probability to be created by others before.
Well, the ABC problems are very typical and there're usually some ingenious, frequently-used tricks in it. I think CF865D (ABC250G) is a very nice problem which made me learn more about greedy algorithm. Certainly, it is not good to post previous problems. But rating is not the most important thing. We can learn something through the contest, that's enough!
Yes, it would be much better to think that way. I just hope that the writer can make enough effort writing the description that it can hardly be searched, then it seems will become more fair.
I totally understand where people are coming from wrt to not wanting repeat problems. After all, people who have seen the problem before have an 'unfair' competitive advantage. Personally, I'd prefer no repeat problems, all entirely novel.
However, I really don't mind repeat problems, so long as they are sufficiently interesting. I do CF for fun: as long as the problem is fun, it's a good problem :). It's okay to have some overlap. Obviously, too much overlap makes a problem boring...