atcoder_official's blog

By atcoder_official, history, 2 years ago, In English

We will hold AtCoder Beginner Contest 352.

We are looking forward to your participation!

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2 years ago, hide # |
 
Vote: I like it -12 Vote: I do not like it

Yay, hope to solve E and F.

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2 years ago, hide # |
 
Vote: I like it -20 Vote: I do not like it

Good Luck!Hope F!

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2 years ago, hide # |
 
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Bad luck and low rating!

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2 years ago, hide # |
 
Vote: I like it +6 Vote: I do not like it

Good luck!- Hope to solve F and G.

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2 years ago, hide # |
 
Vote: I like it -15 Vote: I do not like it

for problem E , what's the part of my solution that giving a TLE ? is it constructing the graph ??

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2 years ago, hide # |
 
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I don't understand. Why does my code WA on 4 testcases?

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2 years ago, hide # |
Rev. 3  
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Can anyone help me why I am getting WA on 2 testcases for this solution of F?

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2 years ago, hide # |
 
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what's the idea behind F?

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Rev. 3  
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Hello! I'm just a mediocre problem setter who is wondering how to give many many many D&C NTT problems which has almost the same solution quickly. May Atcoder Beginner Contest help?


UPD: I don't know whether ironies are just unwelcomed in codeforces or it's not the right place to discuss a problem which has only 143 solves with many newbies? Please, tell me the reason if you decide to downvote me @_@.

UPD 2: Maybe next time I'll try "DCNTT in ABC G author's solution, are you retarded?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????".

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    2 years ago, hide # ^ |
    Rev. 3  
    Vote: I like it +19 Vote: I do not like it

    Of coz,ABC is a great way to improve your poly skill quickly.

    UPD:In fact I agree with _istil's opinion.I think he's not saying that D&C NTT problems are not good,but too many similar D&C NTT problems in ABC are not interesting.

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    2 years ago, hide # ^ |
     
    Vote: I like it +40 Vote: I do not like it

    They are meant to be educational for beginners, as it says in the name. ARCs and AGCs are held to (much) higher standards.

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      2 years ago, hide # ^ |
       
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      I think it's not educational to put many tasks with a same algorithm again and again. It's just a sign of lack of responsibility and lack of time to polish a contest.

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    2 years ago, hide # ^ |
    Rev. 2  
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    probably you don't know that atcoder has acl and you can just call convolution in your solution without knowing what is ntt

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      2 years ago, hide # ^ |
       
      Vote: I like it +5 Vote: I do not like it

      That is indeed helpful during contest time. But that doesn't help me learn the algorithm itself. Am I just participating in ABC only for getting a higher rank?

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        2 years ago, hide # ^ |
        Rev. 2  
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        I am trying to understand your frustration. if author's solution used std::set / std::map how much author is retarded?

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          2 years ago, hide # ^ |
           
          Vote: I like it -21 Vote: I do not like it

          Are you saying: if author's solution contains int main() how much author is retarded?

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            2 years ago, hide # ^ |
             
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            please no puzzles just answer

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              2 years ago, hide # ^ |
               
              Vote: I like it -12 Vote: I do not like it

              Am I not clear? If you don't have the ability to hold a good ABC round every week, hold it every two weeks. If you cannot educate beginners but just keep creating trashes, stop using the name "beginner contest" but "atcoder library contest". If you cannot come up with a different G-placed problem from NTTing, stop posting problems for Atcoder and leave the company. In reply to your question: std::set and std::map are STL containers, and you are sure to learn them long before you understand how a balanced search tree works.

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        2 years ago, hide # ^ |
         
        Vote: I like it +9 Vote: I do not like it

        I'd rather agree with unpopular opinion of _istil.

        1. I completely don't understand the point of ACL. What is it designed for? I never use it and never will, because I try to improve or at least to keep up my coding skills, first of all. Also, for those who can still participate in official onsite contests, it is really harmful and, I suppose, many of real beginners will suffer from not being able to implement any specific variety of data structure adjusted to specific problem's requirements when they have no access to online resources and ACL. If they need to take a higher place and get more rating, that's completely their choice, although I don't really think it is quite educational.

        2. As for the name "AtCoder Beginner Contest", it's really misleading. Despite being not really high-rated lately, I wouldn't call myself a beginner. However on average I solve only 6 problems out of 7. Actually, at least a couple of problems are tricky and educational in almost every round, and they genuinely require a certain effort from me. And normally problem-setters should at least try to avoid similar problem ideas in adjacent contests, which may not be the case for ABC, unfortunately. I think this what _istil meant if to throw away the emotional wording.

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2 years ago, hide # |
 
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loved F, thank you for contest!

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    2 years ago, hide # ^ |
     
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    What was the method for F? I was roughly trying to brute force on all non-trivial connected components, (each connected component of size > 1), because I knew 16! would be too slow, but 16 * 8! might pass.

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      2 years ago, hide # ^ |
       
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      Yes, you can actually do brute force, but instead of factorials think about placing components.

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2 years ago, hide # |
 
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Solved D with a segtree

All I can see now are segment trees

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2 years ago, hide # |
 
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"Yes" != ("YES" || "yes").

LOL, still case sensitive on output strings.

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Randomized solution for F gave me some hope for a moment

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For E, I forgot to handle this disconnected case:

Spoiler

My submission still gets AC, even though I didn't output -1 for the above case.

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Could someone help me debug E? I've been absolutely confused for the second part of the contest and still can't understand where the WA is coming from: https://atcoder.jp/contests/abc352/submissions/53123170

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    2 years ago, hide # ^ |
    Rev. 4  
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    Fails on following testcase.

    Spoiler
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Good luck !!!

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Speedforces and Speedcoder :)

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Rev. 2  
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E Submission

What's wrong here?

Spoiler
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2 years ago, hide # |
 
Vote: I like it +28 Vote: I do not like it

When you join the contest late by $$$5$$$ minutes and get $$$F$$$ accepted after the contest end by $$$4$$$ minutes:

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2 years ago, hide # |
 
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I would like to share my solution to problem F(taking me about 90 minutes to get accepted), as follows:

  1. Divide all the nodes(people) into several connected components, and suppose that there are cnt of them

  2. For each component, compute all the feasible rankings, and denote them based on bitmasks

  3. Use dp[i][j] to denote that, for the previous i components, whether we can achieve the state of j or not, and also use set last[i][j] to store the previous states that can reach j. Here, the state means the bitmask of rankings

  4. The final state should be (1<<n)-1, and we start from last[cnt][(1<<n)-1], and check whether the current state is unique or not. If it is unique, then we have unique rankings for the nodes within this component

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2 years ago, hide # |
 
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can anyone figure out where i am going wrong in E. https://atcoder.jp/contests/abc352/submissions/53149749

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2 years ago, hide # |
 
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Can anyone give a hint on how to optimize problem E?

I did understand the part where we could build a graph from all the given weights (using DSU) and then apply Kruskal to find the MST, but I saw the limits on K and understood this solution would result in TLE.

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    2 years ago, hide # ^ |
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    Recognize that some of the edges are redundant and use minimum spanning tree algorithm, kruskal or prims. For example on ignoring redundant edges, you only actually care about joining nodes into the minimum spanning tree if they are disjoint. And you can join all nodes to just a single node representative of a connected component.

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2 years ago, hide # |
 
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Can someone help me with problem E? Why my code is giving wrong answer on some test cases, even though I have also used the same logic as most others. Submission

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to solve $$$E$$$ do I need to learn any algorithm?

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Vote: I like it +1 Vote: I do not like it

this contest was totally fixed and made me bored. abc352 is one of the boring contests ever. abc352 fixing and boring. abc353 is genuine and much interesting with sigma problems.