sevlll777's blog

Codeforces Round 1004 (Div. 1, Div. 2)
By sevlll777, 5 weeks ago, In English

Hello again, Codeforces!

I am glad to invite you to Codeforces Round 1004 (Div. 1), Codeforces Round 1004 (Div. 2), at Feb/11/2025 17:35 (Moscow time).

In Division 1 you will be offered $$$6$$$ problems. In Division 2 you will be offered $$$7$$$ problems. One of the problems in Div.1 will be divided into 2 subtasks. Round duration is set to be 2 hours.

Also, both divisions contain at least one interactive problem(s), so be prepared for those! Guide for interactive problems

I would like to thank,

As always, we hope you will like the problems. Have fun!

Score Distribution:

Div. 1: $$$750$$$ — $$$750$$$ — $$$1250$$$ — ($$$750$$$ + $$$1250$$$) — $$$2000$$$ — $$$3000$$$

Div. 2: $$$500$$$ — $$$1000$$$ — $$$1250$$$ — $$$1750$$$ — $$$1750$$$ — $$$2250$$$ — $$$3000$$$

UPD: Editorial

UPD2: We sincerely regret to inform you that we have discovered a bug in the interactor. A series of tests is currently underway to assess the full impact of this issue. Once we have the results, we will provide a detailed update. We deeply apologize for this incident and any inconvenience it may have caused.

UPD3: After the analysis, it was determined that this problem affected a small number of participants. There are no submissions that get AC with the correct interactor and erroneously received a non-AC verdict earlier. Therefore, the following decision was made:

If your solution worked with the old interactor, but does not work with the correct one and your rating has decreased, then the round will be unrated for you.

UPD4: Congratulations to the winners!

Div.1:

  1. Kevin114514

  2. tourist

  3. Radewoosh

  4. turmax

  5. heuristica

Also, special thanks and congratulations to rainboy for being one and only one solving problem F in division 1!

Div.2:

  1. Morisz10

  2. Wxssim

  3. Aurora14526

  4. shardulisgapryongkim

  5. igAC

  • Vote: I like it
  • +294
  • Vote: I do not like it

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5 weeks ago, # |
  Vote: I like it +11 Vote: I do not like it

As a tester, I must say, FairyWinx is so orz.

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

hmm unusual score distribution D and E are same

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5 weeks ago, # |
  Vote: I like it -227 Vote: I do not like it

As a tester, I have a proof that upvoting this comment will lead to positive delta. But the proof is too long to fit the margin.

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5 weeks ago, # |
  Vote: I like it +19 Vote: I do not like it

Good luuuck Everyone

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

Hello, could someone please tell me when Codeforces typically runs the plagiarism check? For example, how many days after a contest does it occur? Also, for round 1002 div 2 , have the plagiarism checks (and the process of skipping certain solutions) been completed, or are they still pending?

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    4 weeks ago, # ^ |
    ← Rev. 2   Vote: I like it +1 Vote: I do not like it

    they run them randomly ig. and yes they're pending since a long time

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5 weeks ago, # |
  Vote: I like it -133 Vote: I do not like it

Authors should know that many aren't participating in rounds that have interactive problems, it's not good for you.

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

    I do not think so. Always avoiding interective problems is not good for your coding ability.

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

    Just write interactor in ~5 minuts and will be happy)

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

    What's wrong with an interactive problem? It's not like they are that different from regular ones, all that really matters is that they force you to answeer queries online, opening up a lot of interesting possibilities

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5 weeks ago, # |
  Vote: I like it +18 Vote: I do not like it

Bring Reporting Option in Codeforces MikeMirzayanov , so that the community can help cleaning away cheaters.

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

    I saw some YouTube streamers providing solutions during the contest today.

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5 weeks ago, # |
  Vote: I like it -7 Vote: I do not like it

Every problem starts with Hello-World but ends with infinite possibilities

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5 weeks ago, # |
  Vote: I like it +12 Vote: I do not like it

As a tester, FairyWinx orz

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4 weeks ago, # |
  Vote: I like it +1 Vote: I do not like it

As a tester, I should say, setters made one of the best interactive problem I've ever seen

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4 weeks ago, # |
← Rev. 2   Vote: I like it +9 Vote: I do not like it

As a coordinator, instead of disliking the post, disliking my comment!

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4 weeks ago, # |
  Vote: I like it -10 Vote: I do not like it

my aim of this contest is to get rating 100+

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4 weeks ago, # |
  Vote: I like it +21 Vote: I do not like it

Div.1 A=Div2. C or E?

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

    Usually, div 1 A = div 2 C

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      4 weeks ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      But if div 1 A = div 2 C, Div.1 D should be Div2.F, but Div.2 F isn't divided into 2 subtasks.

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        4 weeks ago, # ^ |
          Vote: I like it +14 Vote: I do not like it

        Maybe they didn't just copy and shift the problem set, or used only the easy version of div 1 D in div 2.

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    4 weeks ago, # ^ |
      Vote: I like it +19 Vote: I do not like it

    I think this time Div 1A=Div 2D

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

As a tester, problems are exciting. I recommend participating, and wish you good luck and have fun.

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4 weeks ago, # |
  Vote: I like it -13 Vote: I do not like it

Finally, interactive problems are coming...

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

hello

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4 weeks ago, # |
  Vote: I like it -19 Vote: I do not like it

Wish to reach Master!

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

why there are different score distributions in div1 and div2 ?

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4 weeks ago, # |
  Vote: I like it +7 Vote: I do not like it

Hi! coders.

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

This might be a round where tourist will get his badge back ||

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    4 weeks ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    +160??? awwww

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

    It is not realistic even if he gets Rank 1 !! They don't get so much positive delta at that level..

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

Also, both divisions contain at least one interactive problem(s), so be prepared for those!

After a long time, yeahhhhhh

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4 weeks ago, # |
  Vote: I like it +3 Vote: I do not like it

I'm a bit confused on how to efficiently write code for the interactive problems

From the linked post: "Input/output in interactive problems works much slower than in usual problems — try to use scanf/printf instead of cin/cout in С++, BufferedReader/PrintWriter in Java and etc."

Does this mean in Java, we should use BufferedReader/PrintWriter? Or that instead of using Bf/Pw we should use scanner?

And if the former, I guess all I need to do is write pw.flush() at the end of my code and it should behave somewhat benign?

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

    You should flush after every output you make so that your query is not buffered and the interactive checker processes it instantly. Also, I have never really had problems with the performance on interactive problems, cin/cout were enough for me

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

From the score distribution, I would guess the 2 Div. 1 750s are the same as the 2 Div. 2 1750s.

Then the Div. 1 1250 = Div. 2 2250

And then Div. 1 2000(not the (750+1250) one) = Div. 2 3000

Now I'm thinking why they did not put the (750+1250) one in Div. 2.

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

    There are already 7 scoring opportunities in Div2.

    I'm guessing they didn't want to increase it even more to 8 so put the hard version only in Div2.

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    4 weeks ago, # ^ |
      Vote: I like it +20 Vote: I do not like it

    We considered D2 and E in Div.1 similar in terms of difficulty (as can be seen form score distribution). And since D had subtask it made sense to place it earlier in Div1. However, for "dead last" position in Div.2, we thought Div.1E is more appropriate, mainly because otherwise both Div.2F and Div2G would be some dp/combinatorics, and with Div1E we achieved some sort of topic balance in Div2.

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4 weeks ago, # |
  Vote: I like it -88 Vote: I do not like it

I very like problems like "C+K+S".I want contest writer make more this problems in contest.

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4 weeks ago, # |
  Vote: I like it +7 Vote: I do not like it

facts:

  • after 15 hours, i have to hand in my winter vacation homework
  • there are still 3 writing tasks (600 Chinese characters each) to be done
  • i don't want to do them
  • if i don't finish them, my mom might not let me to use the computer in the evening
  • i just found out there is a cf round this evening, which has a great chance to give a positive delta

:(

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

I can't wait to take part in this anticipated contest!

This is my first (Div. 1, Div. 2) contest. I hope the qualities of the problems will be satisfactory.

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4 weeks ago, # |
  Vote: I like it -18 Vote: I do not like it

As a participant,I am not a tester.

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

It would be cool if everyone got their nickname as a title

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

    That would spoil the fun of competing in my opinion..

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4 weeks ago, # |
  Vote: I like it +40 Vote: I do not like it

As a positive delta, wish everyone a participant!

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

nvm

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

my target pupil.

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4 weeks ago, # |
← Rev. 3   Vote: I like it 0 Vote: I do not like it

it was an observatory problem

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

Sorry for writing this in between the contest (I solved what i can and cant do the next one)

curiously I locked my problem and went to see room (i have never hacked a problem before)

i saw a solution (ofc i couldn't hack it) and went back

will this count as an "Unsuccessful hack" ?

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

    No. Only when you submit your data or generator and the code doesn't have any errors, will it be considered as an unsuccessful hack.

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4 weeks ago, # |
  Vote: I like it +26 Vote: I do not like it

Unacceptedforces

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4 weeks ago, # |
  Vote: I like it +29 Vote: I do not like it

Div2C is some cancer.

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

    this contest consisted of problems that I'm just weak at... especially C.

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

      I looked at C and thought it would be a nightmare since I'm pretty weak at number theory. I tried brute force and it worked first try

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4 weeks ago, # |
  Vote: I like it +16 Vote: I do not like it

Is this contest an attempt at not having GPT-able problems? I enjoyed ABCD even though they kicked my a*s. Didn't really get to try E or F.

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

    Hi, what's your thinking approach for B, I literally didn't got any smart idea to solve it?

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

      after struggling a lot to phrase it in a nice way, I realised that you should try to push along as much as possible from the lowest ones to the bigger ones, of course without getting to the case where you have only one (because then you can't have it in both arrays). This approach is actually O(mlog(m)), where m is the maximum value of the elements in the array.

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        4 weeks ago, # ^ |
          Vote: I like it +3 Vote: I do not like it

        You can do it in O(m) by keeping a frequency array (arr[0] = # of 0s and so on). You can also do it in nlogn (n = number of elements), by using a sorted dictionary with a bbst implementation.

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

        My approach was also similar, but I was confused about intermediate values, like what if newly converted values will disturb parity of intermediate values 1,1,1,1,1,2,2,4 Although for TC shown below, I was able to came up with formula 1 1 1 1 1 1 1 4 (4-1)*2+1>=index(4) Like intermediate elements should occurred twice, simultaneously they should form '4'. Above check should be performed for all elements with odd frequency But didn't worked for multiple cases :(

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

          That is a decent point (about disturbing the parity). However, consider the following: If you started with an uneven amount at a low value you have to give at least 1 of the amount — 2 a higher value REGARDLESS, in hopes of finding another matching uneven in the higher values. If you started with an even, you will continue pushing an even and there is no problem there.

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

            Hi sir, thanks for the explanation.

            Understood your point 1, that if we keep passing uneven amount of values then it will match at some point as per below example Example-1 1 1 1 2 2 3 4 4

            1 1 2 2 2 3 4 4

            1 1 2 2 3 3 4 4

            Also understood your point-2, that we can keep passing even amount as well, we would still end up achieving, even parity of elements Example-2

            1 1 1 1 2 3

            1 1 1 2 2 3

            1 1 2 2 2 3

            1 1 2 2 3 3

            Just one more clarification?

            Can we say we can push element only when at least 3 identical element available in an array?!

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

    how did u solve B, I used the idea that If I want to form k ns then I need k+2 number of (n-1)s. sub Id:305692767

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    4 weeks ago, # ^ |
      Vote: I like it +9 Vote: I do not like it

    there were no intentions to make contest "anti-GPT".

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

      Bro, it was an awesome contest! We want more like this, ones that aren't solvable by ChatGPT

      Thanks for this one :)

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4 weeks ago, # |
  Vote: I like it +26 Vote: I do not like it

trash contest

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

D seemed like such an interesting problem, I wish I had more time to solve it. B was super tricky for me and I'm surprised brute force worked on C

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4 weeks ago, # |
  Vote: I like it +11 Vote: I do not like it

Thank you FairyWinx for delivering me to my coveted Grandmaster title in my two consecutive rounds.

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

who else ask for "? 1 n" instead of "? i j" such that x[i] == 1 && x[j] == n in div2 D/div1 A xD

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4 weeks ago, # |
  Vote: I like it +11 Vote: I do not like it

I miss the days when problem C used to be DP..

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4 weeks ago, # |
← Rev. 3   Vote: I like it +38 Vote: I do not like it

Report a cheater: byteplay_studios solved A~F and published them on https://www.youtube.com/watch?v=8249xj-tyS0

Now I get a surprise because I saw too many newbies solved D, E, F very fast......

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

In B, why the seventh test case is 'No' ? You can make the bags 244 and 244.

pass a 2, pass two times 4, increase two times one of the 2's in the first bag and done. What i'm not seeing? im dumb?

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

    You need to have 3 in second bag to increase 2 second time.

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

    i had same idea, but it is incorrect

    when you increase 2 to 3 .. you can't increase it again.. because you can only increase a number which is in first bag.. the new number 3 is not in the bag now.

    hope this helps

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    4 weeks ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Choose a number from the first bag that is also present in the second bag and increase it by one

    Once you increase the 2 by 1, it is no longer in the second bag.

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4 weeks ago, # |
  Vote: I like it +12 Vote: I do not like it

Is this contest actually harder than usual or I am just very bad?

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    4 weeks ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    it was not just you

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

    I feel the same way. At this rate, I should change my name to MaybeSpecialist (T_T).

    Was this contest AI-proof or human-proof? (Not blaming anyone, I'm just here to vent...)

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

Problem D looks easy and inviting but I bet I am missing something.

  1. Sort the array
  2. query arr[0] and arr[n-1] this value can not be smaller than arr[n-1]-arr[0] in case of manhattan
  3. query arr[n-1] and arr[0] this value should be equal to previous value
  4. graph is a tree with 1 extra edge so maximum/minimum pair for 2 cannot be the same value so has to be manhattan

But this is WA so what am I missing?

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

    x = [1,1,2,2] y = [2,x,x,1] //hidden treat this as a graph y = [4,x,x,4] // hidden treat this as manhattan

    both queries return 1, in both cases.

    your idea is on the right path. However you can have this case, where you have a cycle from u -> v -> u, where u->v and v->u have the same length

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      4 weeks ago, # ^ |
      ← Rev. 3   Vote: I like it 0 Vote: I do not like it

      What do you mean by y = [2,x,x,1]? Could you give a concrete example with x and y values?

      I interpreted it as the 2nd and 3rd values in y are the same. I think you meant they can be any valid values.

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

        yes, any values. it doesn't matter for our queries.

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

    Sorting the array messes up the indices. You wanna query the index of 1 and index of n.

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

    Thanks tiojuan and bramar2 I misread the problem about query values and if its arr[i] the index or the value. Pretty easy now that I read the question careful got AC. Thanks I had to read the comment again to rethink about my queries.

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4 weeks ago, # |
← Rev. 3   Vote: I like it +87 Vote: I do not like it

Can anyone confirm why my hack on Div1A/Div2D is unsuccessful? Am I hallucinating? 305640270

My test is

2
4
1 2 3 2
2 1 2 3
A
4
1 2 3 2
2 1 2 3
B

Cannot distinguish A and B by querying (1, 3) and (3, 1); since the shortest paths are 1->2->3 and 3->2->1; both are lengths of 2, and manhattan distance is |1-3| + |2-2| = 2

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

    But why query that? I just query 4 1 and see that there is no path leaving 4

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      4 weeks ago, # ^ |
      ← Rev. 2   Vote: I like it +3 Vote: I do not like it

      Haven't you tried hack once?

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

        I didn't read the question properly. Tested it locally and it seems to answer B in both cases.

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

    I have tried it by using test:

    1
4
1 2 3 2
2 1 2 3
A

    And the program's output is B. I want to know why as well.

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

    I also had an unsuccessful hack against 305657749 with a similar test case, it seems like there's something wrong with the interactor.

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

      Thanks for confirming! Now I think I can sleep well for my work tomorrow...

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      4 weeks ago, # ^ |
      ← Rev. 2   Vote: I like it +23 Vote: I do not like it

      Also, this submission 305637703 should pass test 1, as it is correct when tested locally. However, the interactor returns WA on test 1.

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

        Yes, we find bug in interactor, but this submission fails on tests

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          4 weeks ago, # ^ |
            Vote: I like it +11 Vote: I do not like it

          This submission is wrong. I'm complaining because I looked for format error for about 20 min due to this submission and the lack of interacting process for the sample.

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            4 weeks ago, # ^ |
              Vote: I like it +11 Vote: I do not like it

            I'm really sorry about this, and now we're thinking about what to do and how many people it affected

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              4 weeks ago, # ^ |
              ← Rev. 3   Vote: I like it +20 Vote: I do not like it

              Funny thing is, after the rejudge my two WA 1 become WA 2, got another -100 and I would probably lose more rating than I already did.

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

                Retesting is currently underway(

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

                Btw, your solution is correct

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                  4 weeks ago, # ^ |
                    Vote: I like it +24 Vote: I do not like it

                  I mean originally the two WA 1 don't count as resubmit but now they do. The change is minor but this whole thing is just hilarious.

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          4 weeks ago, # ^ |
            Vote: I like it +10 Vote: I do not like it

          What was the bug in the interactor?

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            4 weeks ago, # ^ |
              Vote: I like it +18 Vote: I do not like it

            We skip edge x_n -> y_n

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              4 weeks ago, # ^ |
                Vote: I like it +8 Vote: I do not like it

              Wait... If we ignore an edge, the graph will not exist any cycles. Does this mean that many incorrect solutions that do not check for cycles could pass this problem?

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

                Wait, can't you still have smaller cycles anyways?

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

                This is false, 1->3 2->1, 3->2, 4->1

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

      Hack correct :)

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

        this is not fair to the contestant since he wasn't hacked in contest, i think you should keep the contestant's points (or in general take a bigger look at what is fair, such as giving an option to unrate people whose verdicts might change).

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          4 weeks ago, # ^ |
          ← Rev. 4   Vote: I like it +34 Vote: I do not like it

          It's not the final decision or anything. We are still investigating how much impact this issue dealt to a contest. I guess we certainly will not reject people who had AC in contest, only because of interactor bug, since it is similar to "weak tests" situation.UPD: no,sorry:( .An announcement will be made eventually, when investigation is complete.

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

    I think that the interactor have some problems which make the system has given the wrong shortest paths. But I trust this test can really make the submission give the wrong answer.

    I don't know if the problem's author can upload the interactor of this problem and it may give the actual reason.

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      4 weeks ago, # ^ |
      ← Rev. 5   Vote: I like it -8 Vote: I do not like it

      And the interactor hiding the interacting process makes this mistake totally unbearable.

      Edit: To clarify, if the interaction process had been visible, the bug in the interactor could have been found and fixed immediately. The bugged interactor incorrectly calculates the shortest path in the sample, and many contestants could have noticed the bug right away.

      However, due to the lack of interacting process, these contestants gets WA 1 with misleading information from the interactor. As a result, they wasted time debugging the sample for a non-existing problem, making this mistake somewhat unbearable.

      In my opinion, contestants whose submission initially got WA 1 during the contest and later changed to WA 2 after the bug was fixed were also affected by the bugged interactor, not just those who gets WA after fixing the bug. To the best of my knowledge, there are several such cases.

      Edit2: Softened my tone in Edit section a little bit ^w^ (original version in Rev. 4)

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

I used BFS for C and kept getting a Time Limit Exceeded (TLE) error. Can anyone suggest the correct way to solve this task? here is one of my sub: https://codeforces.net/contest/2067/submission/305699504

tysm btw ^-^

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

How do I even begin to solve problems like this one's B? One hour of thinking only to give up because I'm totally clueless.

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

    Same

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

    What helps me solve questions like B is going through the testcases. We have an operation and we need to figure out when should we use that operation.

    One question I got while going through testcases was: Suppose you have 4 1's: 1 1 1 1, should I leave it as is, as it is balanced or should I increase two of 1's to 2's: 1 1 2 2?

    The following sample testcase made me realize it is always best to increase whenever possible as the incremented nos. might help in the future.

    8

    1 1 1 1 1 1 1 4

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4 weeks ago, # |
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Couldn't even solve B, have to go back to the drawing board now. How's B becoming a pain to me is beyond my understanding.

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

    welcome pupil

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

      I felt terrible after the contest for solving only A, but am starting to feel better now after seeing others having the same struggle

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      4 weeks ago, # ^ |
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      Not able to solve problems in contest is way painful to me than loosing some rating. Rating means nothing to me.

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

        youre right you can gain the rating you lost if you study

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

C is one of the worst problems ever, why would you put a bruteforce problem as div2C? Problem B seemed weird too, I think this is what they meant when they were talking about anti-GPT problems. On the other hand I really liked problem D, unfortunately I didn't get further than problem E because I spent too much time on B and C.

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

guessforces

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4 weeks ago, # |
  Vote: I like it +12 Vote: I do not like it

This is a contest that you thought was inexplicable before knowing the solutions, but felt extremely foolish after knowing them.

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4 weeks ago, # |
  Vote: I like it -73 Vote: I do not like it

Wtf Kevin114514? Explain yourself please.

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

My submission failed pretest 1, even though it passes on my local machine.

https://codeforces.net/contest/2067/submission/305693896

Any idea why this happens?

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

    i must be strictly less than 10 as you only have 10 elements in the array, but you were iterating up to 10, which means you accessed an 11th number that's a garbage value.

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4 weeks ago, # |
  Vote: I like it +7 Vote: I do not like it

Problem setters took AI a little bit seriously :)

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

I've managed to properly think only about ABC.

  • A: a bit complex A, I had to write smth down on paper to solve it.
  • B: lol, I got stuck on B for 90 minutes, 3WAs and it seems that I solved it in the end.
  • C: requires guessing a "small observation", I don't really like such problems;

Personally, it was a very great experience to not back down after such a failure at B (huge bad luck + small skill issue), keeping emotioins at bay, and then figuring out C (good luck). Enduring such a variance in one contest is amazing if you don't give up.

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    4 weeks ago, # ^ |
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    what is observation in C . please tell

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

      If you add nines then you only add fixed number of nines. Then just bruteforce.

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

        oh thank you for sharing your idea.

        I did something similar but couldn't prove anything .. fingers crossed for system test

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

          Can you tell an approach about a i tried making some pattern like x should be equal to y-1 and when x is divisible by 9 check for 1 and something like that but it failed can you tell me your approach?

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            4 weeks ago, # ^ |
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            I am sorry I don't have a concrete proof but this is what I did

            I was hoping that imagine one of the digit 'x' in the input will be converted to 7 ... so we just put 9 for that digit ... meaning if we are targetting 3rd digit.. we can keep adding 999 till 3rd digit become 7...

            and I did this for every digit

            so first keep adding 9.. then keep adding 99, 999, 9999 , till you cover all digits .. and find the minimum among all these digits

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

B and C felt very tricky to me .. hoping to pass system test because I didn't prove them much rigorously and just went with intuition

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    4 weeks ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    I cannot even prove correctness of my solution to A

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

      ha ha LMAO.

      I google plot of sum of digits graph and was able to make an observation from there.

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4 weeks ago, # |
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Am I the only one who couldn't solve A even tho solved B-C?

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    4 weeks ago, # ^ |
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    whoa thats crazy, did you struggle with the case where after 9 the sum gets decreased ?

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      4 weeks ago, # ^ |
      ← Rev. 7   Vote: I like it 0 Vote: I do not like it

      I did a little mistake.. My code :

      int tc; cin >> tc;
while (tc--) {
    int x, y; cin >> x >> y;
    if (abs(x - y) == 1) {
        cout << "Yes\n";
        continue;
    }
    bool ans = false;
    if (x > y and (x - y + 1) % 9 == 0) {
        ans = true;
    }
    cout << (ans ? "Yes\n" : "No\n");
}

      I didn't check that x have to be smaller then y when check abs(x — y) == 1.

      -_-dump..

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        4 weeks ago, # ^ |
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        oh no, I am sorry to hear that.

        wishing you all the best for upcoming rounds

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

    I only solved A, Brute from 1 to 1e9 and found pattern :)

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      4 weeks ago, # ^ |
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      actually I googled for sum of digit graph and I got idea from their.. ie I got the pattern observation from there.

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    4 weeks ago, # ^ |
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    me too couldn't solve A :(

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    4 weeks ago, # ^ |
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    lol me too

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4 weeks ago, # |
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i tried doing c by adding 9's and incrementing ans , whats going wrong in this? Can anyone explain.

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    4 weeks ago, # ^ |
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    May not be optimal. Did you just try with 9s or even tried 99, 999, ... which can go TLE but not wrong?

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      4 weeks ago, # ^ |
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      I just kept adding 9s only and for each addition I check for the sevens

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

The contest was a little too hard for me- Gotta grind more I guess...

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4 weeks ago, # |
← Rev. 2   Vote: I like it +16 Vote: I do not like it

I want to report a cheater... pasit used AI in many contests... Including this contest (Div2) (I think he uses AI in problem E and F. He used AI to generate the code, then change the variable name.)

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4 weeks ago, # |
  Vote: I like it +1 Vote: I do not like it

I can not believe C is brute force. I spent the whole contest trying to come up with some crazy rules and they kept failing every time.

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4 weeks ago, # |
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I have no idea how I passed B and C lol. I just guessed something, and it passed.

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

I want to know c problem is Once you've chosen the 9 form, can't you change it anymore?

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    4 weeks ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    In C, the maximum answer which can we obtain is 7 operation, so you write (10!*6) and it worked. It took 1800ms. But it passed.

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4 weeks ago, # |
  Vote: I like it +2 Vote: I do not like it

I am sorry if this is dumb but how is the brute-force solution of problem C faster than the BFS solution. Cant people just make a very big testcase for which bruteforce solution reaches max time.

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    4 weeks ago, # ^ |
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    Smart Brute force will not fail in any case !! People just need to figure out that minimum operations would never exceed 10 (I guess it should be 7, but doesn't have a formal proof) and even if they go for all 9999....999 till 1e18 that would take 18 iterations and for all the iterations at most (say 10) operations :- in total 180 operations for a single testcase !! 180 * 1e4 = 2e6 (won't fail even if you add log factor for digits) !!

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    4 weeks ago, # ^ |
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    and in BFS solution which I did and got TLE; we are checking for all 18 numbers or whatever at each possible number which is not a good choice.. It's better to use a same number (999...999) and keep on performing operations until it contains 7 !!

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4 weeks ago, # |
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Why is pretest 1 failing on CF but not on my laptop?!

It passes on my local machine. But the output shown on CF is totally different, causing pretest 1 to fail. Please let me know why this happens. Some other test might fail, but how is pretest 1 failing?!!

https://codeforces.net/contest/2067/submission/305693896

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

    Your vector v only contains 10 elements, but you are accessing v[i] with i up to 10, so it causes undefined behavior.

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      4 weeks ago, # ^ |
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      It worked on my local machine. I dont know how! :)

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        4 weeks ago, # ^ |
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        try to add #pragma GCC optimize("Ofast") before all your code in local and delete it before you submit your code.

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

        My guess is that the 8 bytes in memory after v on your machine were all 0, so it didn't affect your answer, while on CF they were some big number with a 7 in it, so the answer is always 0 or 1 because you can just add this big number to get a number with a 7.

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      4 weeks ago, # ^ |
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      On making this change, the all the tests pass. I got AC. But it is still weird how the original solution passed on my local machine.

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

        No, it's not weird, you can read some C++ documentation about undefined behavior. Basically when it happens, you cannot predict what your program will behave, it will give you any kind of unexpected results, even different results on the same machine.

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

        Some compiler or environment sets default value as zero for debugging mode. maybe this can impact to your case. Uninitialized variable may dependent to your machine and can behavior different with CF server

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

    Thanks to all for replying. Is there any way to detect such overflows in my local machine? I have tried #pragma GCC optimize("Ofast"), but it doesn't solve the problem.

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

I tought like every time A was see and do and wasted minutes.....

NOW I FELL LIKE I AM EVERGREEN.......(hope less).

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

I choose to continue to believe Codeforces Round Div.2 after participating this exciting and interesting round. Thank all problemset designers & testers.

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4 weeks ago, # |
  Vote: I like it +38 Vote: I do not like it

Nice contest. Enjoyed the problems despite being a complete brick. Dont get the point of D1 though (mine trivially solves D2)

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    4 weeks ago, # ^ |
      Vote: I like it +20 Vote: I do not like it

    For me D1 was easier than A (and maybe B), and my solution to D2 approaches the problem from a different direction (for D1 I went from higher to lower, and for D2 from lower to higher and had to check a lot more things).

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      4 weeks ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      i guess i got lucky that my approach generalizes easily then. About difficulties, it seems all of us have very different experiences (after talking with others). Personally I found C < D1 ~ D2 < A < B which is quite funny

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4 weeks ago, # |
  Vote: I like it +65 Vote: I do not like it

Screencast

I always like your problems. Totally went insane on C, but that's obviously my issue, not the issue of the problem.

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

E was very easy, spent all my time on C. leaving would have been a good decision

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4 weeks ago, # |
← Rev. 3   Vote: I like it +8 Vote: I do not like it

Can someone please explain why my code fails for problem B

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4 weeks ago, # |
  Vote: I like it +8 Vote: I do not like it

Finally, specialist!

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    4 weeks ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Can u help me with the second problem I don't know why its giving wrong answer please

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

      My observation- If freq(x) >=3 then we can always convert freq(x)-2 x to x+1 ex- consider (3 3 3 3 3 5) () (3 3 3 3 5) (3) (3 4 4 4 5) (3) (3 4 4 5) (3 4) (3 4 5 5) (3 4) (3 4 5) (3 4 5) Thus its partition can be done This is my code-

          void solve(){
        int n;cin>>n;
        vi a(n);
        for(int i=0;i<n;i++) cin>>a[i];
        map<int,int> count;
        for(int i:a) count[i]++;
        for(auto [a,b]:count){
            if(b>=3){
                count[a+1]+=b-2;
                count[a]=2;
            }
        }
        bool ans=true;
        for(auto [a,b]:count){
            if(b&1){
                ans=false;
                break;
            }
        }
        if(ans){
            cout<<"Yes"<<nl;
        }
        else{
            cout<<"No"<<nl;
        }
 
 
 
    }
     
    int main(){
        int t=1;
        cin>>t;
        while(t--){
            solve();
        }
        return 0;
    }

      PS- I know I'm really bad at explanation

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

        I did something similar What I did is I started Iterating from the largest number possible and I said If that number appears odd number of times I need to have 3 x-1 numbers right ? I maintained a Required array and checked whether actual freq and required are same or less or greater But, if req> freq then I require rer-freq+2 times x-1 . I thought its correct why is it failing I can't get it

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

FairyWinx round = be ready for WA2

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4 weeks ago, # |
  Vote: I like it +44 Vote: I do not like it

Nice problems, Div1B is too nice that I couldn't solve for hours.

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

NICE contest and Problem DIV2E just nice

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

...

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4 weeks ago, # |
  Vote: I like it +69 Vote: I do not like it

We sincerely regret to inform you that we have discovered a bug in the interactor. A series of tests is currently underway to assess the full impact of this issue. Once we have the results, we will provide a detailed update. We deeply apologize for this incident and any inconvenience it may have caused.

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    4 weeks ago, # ^ |
      Vote: I like it -30 Vote: I do not like it

    Also comment for dislike

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    4 weeks ago, # ^ |
      Vote: I like it +7 Vote: I do not like it

    oh hell nah

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    4 weeks ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    Mistakes do happen, and I respect your decision. Can you tell me a bit of information about the following things?:

    • How many people are affected?
    • Is getting WA on the example (while the code should get AC in the example regardless of failing full tests anyway) considered not affected?
    • What happens to the hacks submitted during the contest?
    • How many people with negative deltas are unrated, and caused rating inflation?
    • Does this delta consider initial offset, which for (# contest) < 6, a rating is displayed decremented some?

    Also, regarding weak data:

    Uphacks in 24 hours are happening over and over for the contest for Educational Codeforces and Div. 3 contest. In that case, some AC submissions that passed the pretest during the contest finally fails in system testing.

    The final decision seems somewhat "These submissions finally fail on system testing, and if your solution got WA on the system test, you can make your round unrated. (So only positive deltas are applied)." Why should it be the only case of rounds with uphack? I know good things are good, and asking this kind of question to the problem-setters who made small mistakes seems harsh or blunt in some sense, but I want to know the thoughts behind the decision; it's fine if the thoughts are "good things are good." Because as I wrote in the first place, mistakes do happen.

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

      • ~140 participants received an incorrect answer after correcting the interactor

      • There are were ~5 hacks in total, and apparently they were very unlucky.

      • ~100 maybe

      • don't understand question(

      After all, the mistake is on our side. The format of educational rounds and regular rounds is different.

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

        On detailed explanation of question: You can refer this blog post for detailed rating display. Suppose you are the second time participating codeforces Round and got 500 -> 800 (+300). The internal rating actually went down from 1400 -> 1350 (-50). What about this case?

        About the unlucky ones — why aren’t hacks rejudged just like submissions?

        Format of regular rounds — The point is that even in the regular rounds, you can get pretest passed and systest failed, and this is the current case.

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

LOL, I guess all the solutions have not been judged yet and the rating changes happened XD

An example

MikeMirzayanov is it a bug?

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4 weeks ago, # |
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what about ratings on a problem?!

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4 weeks ago, # |
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can anyone please tell me why this fail on test case 4 i will be gratefull if someone can find the error for me SUBMISSION

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

In problem B of div2 the test case 6 2 2 2 4 4 4 we can make the first bag as 2 4 4 and second bag as 2 4 4 but why the answer is not "YES"

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

    how you convert 2 to 4?

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

      I got it . I forgot that 3 must also be there also bro i need to ask one thing if this problem really belong to 1200 range i saw on clist ?? And how there are more than 7k ac on this problem this is surely more than 1400 range

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

rejudge 305643299 plz, I think it is not a mistake

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

will the ratings be recalculated after judging problem A again?

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    4 weeks ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    I write in the upd3 decision

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

      Sorry, it's not explicitly mentioned and I'm not really sure I understand it correctly. Ratings will be recalculated after the rejudge of A, and then people who get WA on A and have negative delta will become unrated, right?

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        4 weeks ago, # ^ |
          Vote: I like it -20 Vote: I do not like it

        Current standing correct. And if in the current standing you have negative delta and your get non-AC after rejudge for you round will be unrated

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

          So this is not relevant, correct?

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

            Yes(((

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              4 weeks ago, # ^ |
                Vote: I like it +8 Vote: I do not like it

              My solution worked with the old interactor, but does not work with the correct one and my rating has decreased.But why the round still rated for me?

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                4 weeks ago, # ^ |
                  Vote: I like it +8 Vote: I do not like it

                I am sure that my solution was accepted during the contest.

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

                Same here, I'm now receiving RE on pretest 2 due to a wrong assertion in the code. The code I submitted during the contest (and that got accepted during the contest) should fail basically all reasonable test cases. If I had received the RE during the contest, I would have easily fixed the problem. I'm not sure whether the policy also holds for RE or only for WA, but in my opinion it would be fair if it also applied here. Maybe, they'll just make the round unrated for us later.

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          4 weeks ago, # ^ |
            Vote: I like it +35 Vote: I do not like it

          Finally, the situation is as follows:

          1. Rejudge your submission. If it now receives WA instead of AC, it is given the WA verdict.

          2. Now, with the updated contest scores, everyone's rating has been recalculated. If 1) affected you and your rating decreased, then the round will be unrated for you

          This feels wrong to me. Why does 1) hold place? Currently, it is treated as if the 'good interactor' was only available during system tests, but not on pretests. Though it is factually not true – the test that makes the wrong codes fail is actually in pretests.

          Also, if we still treat this whole situation as 'weak system tests', it still feels wrong: Ahmed_Salah7 tried to hack me during the contest using this test. The test should have successfully hacked my solution, but it didn't since the interactor was wrong.

          So if we treat the 'good interactor' to be the part of system test, then in reality, some users like Ahmed_Salah7 should've received their +100 hack points instead of -50, and some others should've been hacked during the contest and should've gotten the time to change their solution so that it handles the wrong case.

          I feel this is kinda unfair. I believe that we can't really do anything great in this situation, but maybe there's another solution: for example, if it affected only a handful of people, why don't we just leave it as it was? ;)

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

            Yes, the situation turned out to be extremely ugly and we tried to find some way out (

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4 weeks ago, # |
← Rev. 3   Vote: I like it 0 Vote: I do not like it

Fun fact: In the Div.2 contest yesterday, there are 19 cheaters in the top 50 contestants.

This is especially unfair to me because I happened to be the rk50.

According to this blog.

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

    Hey could you please tell me are only the last round's ratings rolled back, or are all pending contest ratings rolled back?

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4 weeks ago, # |
  Vote: I like it +21 Vote: I do not like it

My solution worked with the old interactor, but does not work with the correct one and my rating has decreased.But why the round still rated for me?

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4 weeks ago, # |
  Vote: I like it -8 Vote: I do not like it

Oh, the process of solving Div. 2 C for me was strange.

Firstly, I found the answer is small, and then I tried memoization search, but TLE.

Then I found $$$ans\le 7$$$. And I tried to use DFS with numbers $$$9\sim 9999999999$$$, but TLE again.

Then I shortened the DFS range to $$$9\sim 999999999$$$, getting AC.

This process wasted much time, which made me unable to think about the rest of the problems with a clear mind.

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4 weeks ago, # |
  Vote: I like it +38 Vote: I do not like it

According to upd3 I should be unrated. Then why my rating decreased. :(

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

    I meet the same problem.

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

    I meet the same problem. sevlll777 please check it. :(

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

    I meet the same problem.

    In Contest:

    After System Test:

    Nevertheless, I admit it's my fault not to check whether the graph form a cycle, but IMO I should be unrated according to the announcement.

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

    I meet the same problem.

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

    Me too ;(

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    4 weeks ago, # ^ |
      Vote: I like it +29 Vote: I do not like it

    Hello, yes, it must be unrated, apparently there was an error, I'll pass it to Mike

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      4 weeks ago, # ^ |
        Vote: I like it +18 Vote: I do not like it

      When will the rating be fixed. I mean it's already 2 days.

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

what's wrong in my div2 E/div1 B 305690629

please help

UPD : if(arr[i]==0){ zero--; if(zero!=0)continue; }

added this to get AC (skip all 0 other than first 0 )

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

Can someone try to hack my submission for Div1C/Div2F? Feels like it should overflow at 3 * dp[vec[i - 1]] % mod but it somehow passed all tests

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

I think this contest should be unrated. It is extremely unfair to make the participants bear the responsibility for the problem setter's mistake in writing the interactive system.

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

    According to the announcement your submission would be incorrect with both the wrong and fixed interactor, so how does it make a difference?

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      4 weeks ago, # ^ |
        Vote: I like it +23 Vote: I do not like it

      In fact, my solution was correct and should have passed the test cases. If it didn't pass during the contest, I could have spent more time fixing it. However, my rating was not corrected.

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        4 weeks ago, # ^ |
          Vote: I like it +18 Vote: I do not like it

        if your submission passed pretests with wrong interactor but failed with the new one then it should be unrated for you. They must have made a mistake...

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          4 weeks ago, # ^ |
            Vote: I like it +28 Vote: I do not like it

          Maybe rating hasn't been updated yet, because I think many people have encountered the same situation as me.

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    4 weeks ago, # ^ |
      Vote: I like it -33 Vote: I do not like it

    Yes, the situation is extremely ugly, but it affected quite a few people, so the following decision was made

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      4 weeks ago, # ^ |
        Vote: I like it +7 Vote: I do not like it

      Does it include those who got WA 1 during the contest but should be WA 2?

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4 weeks ago, # |
  Vote: I like it +73 Vote: I do not like it

What about the "-50" points for unsuccessful hacks that should have been successful and should have earned +100 points in the contest (+150 points now)? Is this fair?

I also tried to clarify within the contest to check if there was an issue with the hacks in problem A, but no one seemed to care to look into it.

So, can you please FairyWinx either add +150 to my contest score (if that's possible) or make the contest unrated for me?

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4 weeks ago, # |
  Vote: I like it -15 Vote: I do not like it

include

using namespace std;

void solve() { int x, y; cin >> x >> y;

if (x + 1 == y) 
    cout << "YES" << endl;
else if (y == 1 && (x % 9 == 0)) 
    cout << "YES" << endl;
else if (x - y == 8) 
    cout << "YES" << endl;
else 
    cout << "NO" << endl;

}

int main() { int t; cin >> t; while (t--) { solve(); } return 0; }

Your code here...

what is wrong in this? for Problem A)

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4 weeks ago, # |
  Vote: I like it +11 Vote: I do not like it

Wxssim Orz

Been following him since his Blog.

Way to go man! Road to red starts <3

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4 weeks ago, # |
  Vote: I like it +36 Vote: I do not like it

sevlll777 My Div. 1 A passed pretest during contest but failed on pretest after contest, so please unrated the round for me.

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4 weeks ago, # |
← Rev. 2   Vote: I like it +8 Vote: I do not like it

Thanks for taking away my first GM performance in div1. It took me 1 minute to repair my solution to A.

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4 weeks ago, # |
← Rev. 2   Vote: I like it +8 Vote: I do not like it

sto sto Wxssim orz orz

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

why there are different score distributions in div1 and div2 ?

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

Really simple solution for problem B // this is the code ~~~~~ void solve() { int n;cin>>n; vi a(1001,0); FOR(n){ int x;cin>>x;a[x]++; } int extra=0; FOR(1001){ extra+=a[i]; //if extra spend if(extra==1){ cout<<"No\n";return; } else{ if(extra>1){ extra-=2; } } } if(extra&1)cout<<"No\n"; else cout<<"Yes\n"; } ~~~~~

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4 weeks ago, # |
← Rev. 2   Vote: I like it +82 Vote: I do not like it

Excuse me, but why the round isn't unrated for me yet?

As you can see in the contest, I submitted problem A pretty early (after about 14 min), and the reason I only submitted 1 time is I passed the pretest with the old interactor (and also I got an Accepted verdict after the contest too). But my code wasn't correct, so I had a Wrong Answer on pretest 2 verdict after the bug was fixed.

I thought the contest would be unrated for me after a few days, but it has been almost a week already, so I'm curious if the round will be unrated for me in the future or not, and what's the reason for the long delay

Thanks for reading my comment

(Sorry for my bad English skill, I'm not a native English speaker)

(Edit: fixed some grammatical mistakes)

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

Sorry for the mistake in problem 2067B of Codeforces Round 1004 (Div.2). I was using ideone as well and wasn't aware that it had public or private mode. I regret the mistake and will take care not to repeat this in the future. I humbly request you not to block me or issue any penalty. Sorry for any inconvenience caused.

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