piaolianggg's blog

difficulty rating comparison between acm.timus.ru and codeforces?
By piaolianggg, history, 4 months ago, In English

What is the mapping between them? Timus has a lot of problems rated < 200, but they also have problems rated above 10,000. The problems also seem more chaotic. I've done some of the first problems, and even the easiest require some tricky thought, but then if I scroll down to more hard problems, some of those are easy.

Does there exist some statistics for comparing timus and cf problems? Or do anyone whos used both sites have an opinion?

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4 months ago, # |
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It's just a number, why do you care so much?

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    4 months ago, # ^ |
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    If I'm not allowed to care about stuff that can be represented by numbers, why would I even be on this website?

    More serious answer: I just like to set goals based on difficulty. Like practice on codeforces. If I try to do a 2800 problem, I give up quickly. But if its a 2000 problem, I know it will be difficult, but I should be able to solve it if I think about it for a while. Maybe this is a bad habit, but thats how my psychology works. So it'd be nice to have the same for timus (without having to spend a lot of time doing too easy and too hard problems to gain an independent intuition for how the timus scoring system works).

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4 months ago, # |
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CF problem difficulty system is broken one way, Timus is broken the other way. It doesn't really make sense to compare the two. The problem style is very different. Plus most of the problems on Timus are more than 10 years old, and while the difficulty number can change with time (unlike CF), it still has the same drawbacks as trying to practice on old CF problems, if you tried that. For some problems the main difficulty is just thinking and that hasn't changed much in 5 years. For other problems it is the algorithms or standard ideas used, which could have become more popular with time.

I would suggest you to try 2-3 problems with difficulties around 200, 300, 400, 600, 800 to find a difficulty range that is not too easy and not too hard for you, that shouldn't take too much time, and you still will be solving problems which is more useful than searching for difficulty conversion function.

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    4 months ago, # ^ |
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    What's wrong with practicing old CF problems?

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      4 months ago, # ^ |
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      Nothing wrong with that, but you might feel like the problem difficulties are broken.

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    4 months ago, # ^ |
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    Ok, thanks for the response. Separate question: do you not recommend practicing on timus? The reason I wanted to use that website was actually because you recommended it in a blog. But that blog was a while, so has things changed, or do you still think its good to practice there?

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      4 months ago, # ^ |
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      I think it's as good a place as any. My main point is to practice in an archive of problems. I used Timus for historical reasons. I guess the default choice now would be the CF problemset. Here are some points why Timus might be better:

      • On CF there are written tutorials for all the problems and you can always look at the codes of other participants. Which might be tempting to do if you can't solve the problem for some time, and I think it isn't good. On Timus there is (usually) no way to look at the editorial or at the codes of others.
      • Timus has problems mostly from ICPC-style competitions, which cover a wider array of topics. It is very rare to see geometry or some brutal implementation problems on CF.
      • While Timus has many problems (it is an archive), it has reasonable amount of problems. Like, it is somewhat realistic to solve every problem on Timus, or at least 90% of problems, and that is a cool goal. CF problemset has an insane number of problems.
      • Almost infinite amount of problems on CF can lead to you ignoring the topics you don't like and not improving, because you can always take a different problem.

      On the other hand, CF has its advantages:

      • CF is modern, has a nice design, and supports a lot of languages and compilers. It's just nicer to use.
      • The problems are more modern, so you won't miss out on some topics that appeared or became popular recently.
      • There is a lot of infrastructure built for CF. You can use Discord bots that will suggest problems for you to solve and stuff like that.
      • On CF there are written tutorials for all the problems and you can always look at the codes of other participants. I put it in the negatives, but if you can withstand the temptation to take a sneak peek at the editorial before you solve the problem yourself, it is nice to have the opportunity to read how it was intended to be solved after you do it yourself.

      At the end of the day, solving problems on one of the platforms is more productive than debating which platform is better. If you want to try Timus — you are welcome. If you want to stick to CF — it is also a good option.

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