E869120's blog

AtCoder Beginner Contest 112
By E869120, history, 6 years ago, In English

Hello, Codeforces!

On Saturday, Octorber 6th, 21:00 JST, AtCoder Beginner Contest 112 will be held.

The contest information is as follows:

  • Duration: 100 minutes
  • The number of problems: 4
  • Scoring: 100 — 200 — 300 — 400
  • Rated: Yes (for people whose rating is 1199 or lower)

Good luck and have fun!
Let's discuss about the problems after the contest.

UPDATE
1. The contest is over. Thank you for your participation.
2. Japanese editorial is published now. Editorial — Wait a moment for unofficial English editorial.
  • Vote: I like it
  • +20
  • Vote: I do not like it

Comments Comments (21)
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6 years ago, # |
  Vote: I like it +14 Vote: I do not like it

AtCoder doesn't officially share who the writer is, but I can tell that some of the problems in this contest, are written by E869120 and square1001!

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    6 years ago, # ^ |
      Vote: I like it +17 Vote: I do not like it

    Are you sure it doesn't share who the writer is?!

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      6 years ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      Well, I think that AtCoder is not sharing who the writer is, for "ABC Only" contests. They changed the system.
      Still, AtCoder shares the writer of ARC and AGC.

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

C and D are nice problems.

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6 years ago, # |
  Vote: I like it +3 Vote: I do not like it

How to solve c?

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I just brute force the all possible cx and cy and figure out is there any possible H or not.

    Here is my code : link

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      6 years ago, # ^ |
        Vote: I like it +1 Vote: I do not like it

      Can you please explain why to check this condition 

      if (h[i] == 0) {
        mx = max(mx,a + b);
      }

      and this 


      if (mx != -1 && res > mx) return -1;

      ?

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

        Actually my solution got accepted with luckily. If H > a + b hi must bigger than 0. I want to check is there any i which hi = 0 and a + b < H.I had to check is H bigger than minimum a + b or not. I don't know how my first solution got accepted :D.

        Here is correct solution : link

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

Everyone, thank you for your participation.
Actually, problem A and C were written by E869120 and square1001. The other two problems were written by an other writer.

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6 years ago, # |
  Vote: I like it +8 Vote: I do not like it

I think a diagram can be good for explanation of problem C.

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

How to solve D ?

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

    Maximum divisor of M which satisfies (divisor * n) <= m.

    Spoiler
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    6 years ago, # ^ |
    ← Rev. 3   Vote: I like it 0 Vote: I do not like it

    Let assume answer is d. So all elements should divided by d so we can say. ai = bi.d

    1 ≤ bi So we just need to check

    Here is my code :link

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Auto comment: topic has been updated by E869120 (previous revision, new revision, compare).

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6 years ago, # |
← Rev. 2   Vote: I like it +17 Vote: I do not like it

Writer's Editorial for All Problems (in English):

Problem A: Programming Education
Problem B: Time Limit Exceeded
Problem C: Pyramid
Problem D: Partition
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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

To solve problem C i was thinking of a Binary search solution where i would binary search for the height of the pyramid and for every height iterate over all the possible values of Cx and Cy and check if the height and value of Cx and Cy satisfies the conditions. but i was not able to figure out the condition wether to move to the next smaller segment or larger segment. Can someone please help who has solved this problem with binary search.

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Before binary searching, are you sure this function is monotonic ?

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6 years ago, # |
  Vote: I like it +8 Vote: I do not like it

Hey ! Did you guys write this contest ?

This must be your sixth contest then.

Why isn't AtCoder revealing the writers. They should, in my opinion.

Here are my solutions to this contest.

Here is my editorial to D :)

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    6 years ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    Actually the 7th one (if only limiting to official contest, there are also 5 square869120Contests)! Starting from ABC 064, we've also wrote ABC 076, 088, 096, 100, 105, 106, and 112 :)
    ABC 105 was only problem B, and this ABC (ABC 112) was only problem A and C, though.

    And the answer to "why isn't AtCoder revealing the writers of ABC-only Contests (they are revealing ARC and AGC and other sponsored contests' writers) is, I think "the system has changed from some recent ABC-only and since then many people do the writer in a single contest (in other words, only one (group of) writer created one contest)".

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      6 years ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      I remember you guys had a question called Snuke's Favourite Numbers or something like that ... I didn't understand the editorial on that one :)

      When is your next contest ? :)

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