maroonrk's blog

AtCoder Grand Contest 069 Announcement
By maroonrk, history, 5 weeks ago, In English

We will hold AtCoder Grand Contest 069. This contest counts for GP30 scores.

The point values will be 900-1000-1200-1200-1200.

We are looking forward to your participation!

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5 weeks ago, # |
  Vote: I like it -76 Vote: I do not like it

Hope tourist can get rank 1 to stay on the sit of king at Atcoder! P.S.:Sorry for my week English.

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5 weeks ago, # |
← Rev. 5   Vote: I like it -69 Vote: I do not like it

PS: I'm just say problem A. The other problems in this contest are creative and I really like them.

I don't think it's very interesting to take a common problem, dualize it, and then present it as a new problem.

What I meant to say is that I am not against the method of taking a common problem, dualizing it, and then presenting it as a new problem. This is feasible and can be a good way to write questions. It can also reduce the workload for the person writing the questions. However, I do not think that the duality method should be written in the solution, as it shows the writer's lack of care and casual attitude towards the problem.

The solution provided by the question writer should guide the contestants from one point to another in the most straightforward and efficient way possible, rather than using the duality theorem to take a long, roundabout route (even though it might reduce the workload for the writer).

I saw another way to solve this problem in the editorial: I believe this method should be the better solution to the problem because it is easier to think. The original approach should have been an 'alternative solution'

In summary, using the duality theorem to create a problem is acceptable, but I do not find it very interesting to include it in the solution. The "Alternative Solution" is the more interesting approach.

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    5 weeks ago, # ^ |
    ← Rev. 3   Vote: I like it -53 Vote: I do not like it

    What I meant to say is that I am not against the method of taking a common problem, dualizing it, and then presenting it as a new problem. This is feasible and can be a good way to write questions. It can also reduce the workload for the person writing the questions. However, I do not think that the duality method should be written in the solution, as it shows the writer's lack of care and casual attitude towards the problem.

    The solution provided by the question writer should guide the contestants from one point to another in the most straightforward and efficient way possible, rather than using the duality theorem to take a long, roundabout route (even though it might reduce the workload for the writer).

    I saw another way to solve this problem in the editorial: I believe this method should be the better solution to the problem because it is easier to think. The original approach should have been an 'alternative solution'

    In summary, using the duality theorem to create a problem is acceptable, but I do not find it very interesting to include it in the solution. The "Alternative Solution" is the more interesting approach.

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    4 weeks ago, # ^ |
      Vote: I like it +68 Vote: I do not like it

    0 — Don't worry about downvotes. You said something, people didn't agree or didn't like it, whatever, move on.

    1 — You have no way of telling that the problem was constructed as "take a dual of a common problem". I don't even know how you arrived at such a conclusion. The statement sounds very natural, I think it is much more likely that the author came up with a problem and then solved it using duality.

    2 — What is wrong with duality in your opinion?

    3 — "The solution provided by the question writer should guide the contestants from one point to another in the most straightforward and efficient way possible". Why? What does that even mean? "The most straightforward" and "the most efficient" ways are usually different. It is usually very hard to show that some way is the most efficient. So what's wrong with the duality solution? And why do you think that it is not the most straightforward or the most efficient in the eyes of the author?

    To sum it up, I think your comment sounds arrogant and nonsensical. It looks like you just don't like the particular solving method or you didn't like the problem or something, and you are trying to invent some reasoning to justify your opinion. Plus, sorry, but your rating is way too low to have an opinion on AGC problems. I would glide past it, people always whine about the problems they didn't like for any nonsensical reason here. But then you decided to attract more attention by continuously changing the comment and even writing a second one. Now I have downvoted both, you are welcome.

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5 weeks ago, # |
  Vote: I like it +30 Vote: I do not like it

Wonder how many people failed to realize that N-2 is enough, not N-1 on B. TT

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    5 weeks ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    Could you please provide your proof ?

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      5 weeks ago, # ^ |
        Vote: I like it +13 Vote: I do not like it

      You can read their official editorial. My "proof" is obviously wrong since I proved something that is false.

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        5 weeks ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        I noticed that and passed lol. However the sample of the 2x2 grid full of 1s is misleading. I first thought that the real method is just a corner case!

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    5 weeks ago, # ^ |
      Vote: I like it +46 Vote: I do not like it

    same here! It is quite hard to think out of the box, literally :(

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5 weeks ago, # |
← Rev. 3   Vote: I like it +39 Vote: I do not like it

Thanks a lot for yet another great round!

My screencast, even though there is not much going on :)

In B, I have thoroughly proven the n-1 solution on paper :) And in D, I was iterating by adding more cases to my DP (with the same state as in the editorial) based on stress test discrepancies, but the connected component constraint did not occur to me. Maybe I would get it with one more hour :)

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5 weeks ago, # |
  Vote: I like it -36 Vote: I do not like it

Can someone explain TaskB solution in more detail.

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4 weeks ago, # |
← Rev. 6   Vote: I like it -18 Vote: I do not like it

I have discovered a cheating behavior. Please refer to this post for details.

https://mirror.codeforces.com/blog/entry/136473?#comment-1221400

Undoubtedly, he also cheated in the same way in this contest.

upd: This comment received so many downvotes, does it mean that everyone is encouraging cheating? Maybe I should keep silent when I find cheating.

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4 weeks ago, # |
← Rev. 2   Vote: I like it +13 Vote: I do not like it

for problem A i dont know a single thing about duality , primality , linear programming or anything related to the point where i dont understand a single sentence in the editorial not sure how i ended up being 2200 but anyways suggest where to even start learning them

edit : the solution should make sense even without knowing alot about linear programming but looks like iam way too dumb for AGCs

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    4 weeks ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    I think most of the contestant solve it using slope trick though (alternative solution in editorial)

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