O--O's blog

Invitation to TheForces Round #4 (EZForces) [Mashup]
By O--O, history, 15 months ago, In English

Hello, Codeforces!

Here's the invitation link of our discord server for contest discussion and announcements.

We are happy to invite you to take part in our round named TheForces Round #4 (EZForces), which will take place in [contest_time:422264]!

You will have 7 problems in 2 hours.

Our team consists of 4 people: E404_Not_Found, k1r1t0, psychobot, O--O

We wish you will love this round!

Congratulations to winners!!!

  1. BurnedChicken
  2. RDDCCD
  3. oversolver
  4. wuhudsm
  5. Svyat

System tested..

Editorial

  • Vote: I like it
  • +75
  • Vote: I do not like it

Comments Comments (43)
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15 months ago, # |
  Vote: I like it +12 Vote: I do not like it

I like this kind of contests.

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15 months ago, # |
  Vote: I like it +15 Vote: I do not like it

As tester, i dont have anything to say about problems, they are nice i think

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    15 months ago, # ^ |
      Vote: I like it +10 Vote: I do not like it

    As a tester, I think they are great, and rejudging after the contest will give a realistic experience.

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15 months ago, # |
  Vote: I like it +15 Vote: I do not like it

When will the final result be published?

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15 months ago, # |
  Vote: I like it +15 Vote: I do not like it

Is it kind of a div 4 round ? O--O

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    15 months ago, # ^ |
      Vote: I like it +20 Vote: I do not like it

    You can see other contests in my blogs. It is not div 4 round. But some problems are suitable for beginners. Different difficulty problems.

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15 months ago, # |
  Vote: I like it +14 Vote: I do not like it

I loves your contests very much it is really great<3.

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15 months ago, # |
  Vote: I like it +4 Vote: I do not like it

Will be rated?

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15 months ago, # |
  Vote: I like it +1 Vote: I do not like it

Weak pretests and no hacks. What's the point?

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    15 months ago, # ^ |
    ← Rev. 3   Vote: I like it +3 Vote: I do not like it

    You can hack after the round, but it's only available for candidate master+ people because of Codeforces limits, Also the point is to make mashups closer to the Official rounds.

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    15 months ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    Don't worry bro, You can hack after the contest end.

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

is it rated ?

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Why have you hold 3 contests, but the number of the contest is # 4?

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    15 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Hi, you can see first 3 contests in my blogs.

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Contest starts...

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Contest started !

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

please open the others solutions or make tutorial blog for this contest.

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15 months ago, # |
← Rev. 3   Vote: I like it +6 Vote: I do not like it

I find sequence in the problem E from OEIS, and easily solved this problem :)

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

What is the intended time complexity for F and how to solve D?

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

    It's $$$O(n)$$$ for F.
    D: Ternary search over the touching point.

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    15 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    To solve D you can notice that the shortest distance between 2 points is the line joining them, however you also need to touch the river atleast once, so think of a geometric transformation that sends one of Alice or Bob to the other side of the river and then see if you can come up with something.

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    15 months ago, # ^ |
    ← Rev. 2   Vote: I like it +6 Vote: I do not like it

    There are two solutions for this problem, but the expected solution is like this: Reverse (multiply by -1) the width of one of the points and get the Euclidean distance of the obtained point with the other point, It can be proven that the obtained distance is the shortest possible

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15 months ago, # |
← Rev. 2   Vote: I like it +5 Vote: I do not like it

It's strange, but for me ALL notifications during and after contest were "undefined" without any text and so on. I also have nothing in "questions" section. Thus 13th test of C was really evil
After all, I liked problems despite being them relatively easy for me (D was too old and I have seen it before hundreds of time)

Notification
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    15 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    We announced in English during the contest

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      15 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I don't have any notifications (in dashboard) even if I switch locale to english one. I had only one proper notification about "only CM+ can hack". And I haven't switched language... Can it be codeforces bug? I have never had problem with notifications, even if my locale is russian and notification is in english (I think that majority of notifications are in english)

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

@O--O how i am get wrong answer after printing 1e9 instead of 1000000000 here is my submission link regreted code

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    15 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    You should print integer, not double.

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      15 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      but why double was wrong both gives the same output , for n =1 my submitted code printed 1000000000 in my ide :(

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15 months ago, # |
  Vote: I like it +5 Vote: I do not like it

For G, we can tell that the answer is $$$(n+1)(n + 1 - H_{n+1})$$$. Since we don't need to be very accurate, there's a solution in $$$O(1)$$$ where use $$$H_{n+1} \approx ln(n+1) + \gamma$$$

Submission

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    15 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Oh hey, yes I did point this out during the testing, but we decided not to make it too hard and kept the task to $$$O(n)$$$. IIRC, a similar technique is used on "Increasing Sequence Card Game" from Kick Start 2021.

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15 months ago, # |
  Vote: I like it 0 Vote: I do not like it

How can I hack a solution ?

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14 months ago, # |
  Vote: I like it 0 Vote: I do not like it

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

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