aviralarpan3301's blog

What makes atcoder problems so good?
By aviralarpan3301, 4 months ago, In English

I've recently started solving problems on AtCoder and noticed that the quality of problems is exceptional. Obviously Codeforces also offers great problems, AtCoder's seem to be on another level. Does anyone know why this might be? One possible reason could be that AtCoder hosts contests less frequently than Codeforces, allowing them to maintain a higher standard for problem quality .

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4 months ago, # |
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I think less no words in Problem Statement of AtCoder makes it diff from other CP Websites

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    4 months ago, # ^ |
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    That's not what I meant. Ofc the problem statements are short. But I meant, the "idea" to solve the problems are insanely good and imaginative. They use relatively simple techniques in very clever ways.

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4 months ago, # |
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They are "so good" if you enjoy dumb math tricks. If you want codeforces to "maintain a higher standard" like this, just only accept rounds where all problems rely on invariants or variable substitutions, with statements and setups that have even less to do with the a real process you'd want to solve than on other websites.

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    4 months ago, # ^ |
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    I think AtCoder helps you get better in some important algos like Bs or DSU or the dumb math tricks as you said.

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    4 months ago, # ^ |
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    So codeforces is more preferred?

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    4 months ago, # ^ |
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    Controversial statement

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      4 months ago, # ^ |
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      Ask strong contestants (IGM or LGM), and most of them would agree, search for old blogs to see for yourself.

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        4 months ago, # ^ |
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        See for yourself

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          4 months ago, # ^ |
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          What's your point here, the guy in your linked blog was clearly promoting Atcoder

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        4 months ago, # ^ |
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        Agree on what?

        Most high rated people disagree with the guy. That is why the current meta is what it is

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          4 months ago, # ^ |
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          that's why we need more Chinese style rounds

          the first rounds would obviously be downvoted to hell but then the meta will gradually change

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    4 months ago, # ^ |
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    When have CP problems been about resembling "a real process"

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      4 months ago, # ^ |
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      It's not like people made up algorithm ideas for no reason throughout history, and there are cp problems that reflect this. However, higher rated cp people more and more actively choose to make up nonsense instead of ideas that have some resemblance to could be useful, and like to recycle the same few Olympiad combinatorics math tricks in increasingly contrived setups.

      I think good problems are usually made thinking about what is real problem you want to solve and idealizing until solveable. But many just like to mash together random ideas and ask is this setup solveable (and when they come from the same set of math constructions they usually end up recycling the same line of insights), or force a problem onto a solution while trying to hide the inspiration through contrived setup.

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        4 months ago, # ^ |
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        By your standards almost all CP problems are bad. For some topics all problems would be considered bad. It is goal of problemsetters to improve the problem solving abilities of other people. Number theory was useless for most of human history until modern cryptography became important, which was invented through generations of people coming up with new "useless" theory.

        Also I don't understand the "recycling the same line of insights" part. There are examples of those, but you can't tell me that these kind of problems occur all or even most of the time on Atcoder.

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    4 months ago, # ^ |
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    LMAO how many atcoder problems have you solved to make such a bold statement? Seems like you are just salty 'cause you are not able to do maths. I haved solved almost every problem which is <= 3200 rating on Atcoder and none of so-called math problems there require any "dumb tricks" (except for some in AGC, but they are targeted for higher red anyway). For those with 3200+ rating, well they do require some mind-boggling math tricks ... , but, we should not care about it anyway since only IGM and LGM are able to solve them during the contest (the majority of those problems were in ABC for educational purpose FYI). And what do you mean by "less to do with the real process", do you mean that 30-line problem description comprised of nonsense sentences of a bullshit story which have nothing to do with the task itself is better than those with a direct statement on Atcoder ? Though plenty of the problems on Atcoder are ad-hoc / brain teaser / maths but they are very fun to solve and most of those can be done within 20 lines of code.

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    4 months ago, # ^ |
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    I think there isn't much problem rely on invariant or variable substitution in my experience (at least ~ orange, not sure about red~ but probably not much still). And I feel most of the problems from ARC and old AGC can be solved by just proper reasoning and basic combinatoric skill rather than you said "weird math trick".

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    4 months ago, # ^ |
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    AtCoder is just better than Codeforces.

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4 months ago, # |
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i never gave atcoder a real chance only tried afew ABC problems and 1 ARC and left is it really that good ?

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4 months ago, # |
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The problems are straight-forward and are written formally, so you skip the part where you "translate" the statement. I think that's the most significant reason why they are so good.

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4 months ago, # |
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They steal from codeforces

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4 months ago, # |
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Referencing Zhtluo's blog, I think Atcoder is really good because it combines problems of all three types — there are some niche observation based problems, some problems requiring knowledge of particular data structures and some requiring plain heavy implementation. Codeforces is more biased towards observation but Atcoder maintains a fine balance among all "aspects" of problem solving. (This might not be true for Div1Fs and AGCs though, I have never tried those).

Edit: Whoops, I guess that's true for ABCs only.

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    4 months ago, # ^ |
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    This is.....totally wrong.....

    Atcoder has predominantly observation based problems while CF has more implemention/data structure (still a lot of observations problems in CF too, but definitely less than Atcoder)

    It is well known that maroonrk likes problems a certain way and he regards thinking >>> ds as a crucial aspect of any good problem

    I agree with him, and it is the reason Atcoder is so good.

    (This is assuming you dont count abcs as atcoder)

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      4 months ago, # ^ |
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      these new ABCs are total bs, imo ABCs where also "atcoder", in the 100-200 contest ids

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4 months ago, # |
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I think since their problems are very concise. But sometimes it is overdone and you must decipher their use of notation to figure out something that could be more clearly described using language.

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4 months ago, # |
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the same reason anime is better than cartoons

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4 months ago, # |
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I don't know but I recently noticed some problems already appearing in some OJs before the contest.

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4 months ago, # |
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Aoki and Takahashi instead of Alice and Bob

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    5 weeks ago, # ^ |
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    another sad case of affirmative action taking jobs

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4 months ago, # |
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Actually ABC problems are much worse than CF Div3 problems, but ARC problems are really great.

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    4 months ago, # ^ |
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    I thought ABCs were good as someone suggested me if you wanna improve in fast solving then solve ABCs of atcoder they will improve your fast solving. But I haven't solved much ABCs but they are generally easier than div2 can't compare with div 3 though bcz I feel sometimes C of ABCs are pretty good compared to div3 ones

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    6 weeks ago, # ^ |
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    Div2>ABC>Div3

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4 months ago, # |
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