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arvindf232's blog

Codeforces Round #822 (Div. 2)
By arvindf232, history, 2 years ago, In English

UPD: The round has been rescheduled to a different time due to a clash with a CodeChef contest

Hello CodeForces!

Me, AHappyPotato and __jk__ are excited to invite you to participate in Codeforces Round 822 (Div. 2). It will start at 23.09.2022 15:05 (Московское время). The round will be rated for everyone with less than 2100 rating. You have 2 hours to solve 6 problems. Please note the unusual start time.

We would like to take this opportunity to thank everyone who have contributed to our round:

We look forward to seeing you on the leaderboard!

UPD: Score Distribution: 500 — 750 — 1250 — 2000 — 2250 — 3250

UPD2: Editorial

UPD3: Winners!

Div 1 + 2:

  1. GOI_Official
  2. Um_nik
  3. tzc___________________wk
  4. Second_Brave_Niuniu
  5. hitonanode

Official:

  1. GOI_Official
  2. tzc___________________wk
  3. Second_Brave_Niuniu
  4. Sand_Emperor
  5. steven14414
  • Vote: I like it
  • +370
  • Vote: I do not like it

Comments Comments (178)
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2 years ago, # |
  Vote: I like it +96 Vote: I do not like it

As a co-author, the problems are nice and I recommend everyone to join this contest!

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    2 years ago, # ^ |
    ← Rev. 2   Vote: I like it +64 Vote: I do not like it

    As another co-author, I can assure that problems are great and I also recommend everyone to join!!

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      2 years ago, # ^ |
        Vote: I like it +56 Vote: I do not like it

      As a tester and not a co-author, the problemset is very amazing and you should join the contest!

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        2 years ago, # ^ |
        ← Rev. 2   Vote: I like it -56 Vote: I do not like it

        As a participant and not a co-author or tester, i will surely join the contest.

        Why are u downvoting for just no reason.

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

          If you ever ask why people are downvoting you for no reason, just know that you'll get a shit ton of additional downvotes just for that

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

        As another tester, I agree with you!

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          2 years ago, # ^ |
          ← Rev. 2   Vote: I like it +52 Vote: I do not like it

          As a newpie, Downvote me

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            2 years ago, # ^ |
              Vote: I like it +50 Vote: I do not like it

            As a non-ratist, I upvoted.

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

              I wish my contribution would be non-negative (❁´◡`❁)

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            21 month(s) ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            Holy Moly Folly Solly

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

      My translator is so bad that it translates great problems into big problems.LOL

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

Ooh, a very early announcement. This should be good news.

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2 years ago, # |
  Vote: I like it +11 Vote: I do not like it

Hopefully I will solve two problem this time. All the Best to everyone .

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2 years ago, # |
  Vote: I like it +44 Vote: I do not like it

Yaay

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

Very excited to participate, gl everybody

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

My rating is 822. tzc___________________wk

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2 years ago, # |
  Vote: I like it +128 Vote: I do not like it

CodeChef Lunchtime is clashing with this round. After a long time, CodeChef is having a rated contest for div 1. I think many of us want to participate in both the contests so could you change the date or timings of the round (if possible)?
arvindf232 AHappyPotato __jk__

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2 years ago, # |
  Vote: I like it +37 Vote: I do not like it

As a tester... I have nothing to say other than good luck.

-QuangBuiCP

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

in last div 2, i did question 1 very quickly,i figured out question 2 quickly 2 and coded it but wasted my 1 hour just coz i had a wrong value assigned to a variable, made wrong submissions many times, and question three which was very easy i could not figure it out coz i wasted my energy alot on the second one. this is me in literally every contest and im even loosing hope now.can someone please guide me how to fix these issues, i can never maintain pupil due to these sillly mistakes.

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    2 years ago, # ^ |
      Vote: I like it +16 Vote: I do not like it

    you made a mistake, and you will not do it again. Im sure that there a finite amount of doable mistakes, so just attend more contests!

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2 years ago, # |
  Vote: I like it +27 Vote: I do not like it

Hong Kong Round! Support!

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

As a participant, I will participate in this competition to improve my strength

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2 years ago, # |
  Vote: I like it -13 Vote: I do not like it

I hope reach CM after this contest ಥ⁠‿⁠ಥ

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    2 years ago, # ^ |
      Vote: I like it -7 Vote: I do not like it

    i love your graph haha

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      2 years ago, # ^ |
        Vote: I like it -7 Vote: I do not like it

      -100 +100 -100 +100 :'(

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        2 years ago, # ^ |
          Vote: I like it -10 Vote: I do not like it

        any tips for me to reach specialist , other than fast ABC

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          2 years ago, # ^ |
            Vote: I like it -7 Vote: I do not like it

          Practice 1500+ rated problems

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

            I practice 1200-1500, I thought that would help me reach specialist because I struggle with div. 2c 2/5 times during the contest, am I doing it wrong?

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

              yes u should always pratice problems of higher rating than your current one.So donot waste time in 1200 go for 1400+ ones.

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

    Wishing you luck :)

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

lucky

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2 years ago, # |
  Vote: I like it -10 Vote: I do not like it

Plz keep the original starting time but re-schedule to a different day

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    2 years ago, # ^ |
      Vote: I like it +13 Vote: I do not like it

    No way, i think it's much better than before, but each person's experience depends on the local time zone, which is something that cannot be done perfectly ^-^

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

      In my opinion, time zone is not the main problem. What matters more is that it's preponed... And I happen to be one of the unlucky guys who missed this round because of that...

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

Oh,Very excited to participate .

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

The contest has been preponed. Do not miss it! All the best everyone!

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2 years ago, # |
  Vote: I like it +18 Vote: I do not like it

Respect++ For respecting codechef :)

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

i hope get delta >= 5

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

Good luck everyone.

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

sad for west coast :’(

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2 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Just noticed the contest was preponed.

I think postpone is far better than prepone. Many people registered the contest and back online on the time the contest was scheduled. prepone could make them miss the contest, but postpone won't.

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

    I think sending a mail to everyone who registered might be a good idea to avoid that.

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2 years ago, # |
  Vote: I like it +13 Vote: I do not like it

As a uni student who would have been unable to attend this contest due to it being during my classes, I am very grateful for this opportunity.

(Yes it would be 5am in my local time, but I literally don't care.)

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2 years ago, # |
  Vote: I like it -22 Vote: I do not like it

Can you help us ? here -- > World War III will begin D:

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2 years ago, # |
  Vote: I like it +47 Vote: I do not like it

Why is cf accomodating for codechef and not the other way around?

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    2 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    Because codeforces cares for us

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

    Codechef had postponed its previous contest from 21 to 22 Sep. So they are like its your turn now.

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

    CodeChef is holding rated round for div1 after almost a month thus many don't want to skip it. If no contest accommodates it think many will end up giving CodeChef round.

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

As someone waking up at 4:30 to do this contest, please let me solve ABCD.

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

    Only you have to solve the problem. Only way someone else can let you solve a question by giving hints or telling solution which is cheating so you are going to cheat

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

codeforces are very kind for programmer who rescheduled their contest timing because of codechef contest time at same time.

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

Codeforces Language Picker -- chrome extension to fix codeforces language picker.

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

20:05-22:05 UTC+8 is friendly to Chinese!

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

finally, the contest at 9 pm

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

3250.

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

I like this Score Distribution : 500 — 750 — 1250 so much

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

I hope I become expert in this contest... :)

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

UPD: Resolved thanks!

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

My calendar didn't reflect the time update, I am wondering whether I registered from a wrong source. If anybody's calendar works correctly pls let me know, thanks!

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2 years ago, # |
  Vote: I like it +10 Vote: I do not like it

I happen to be one of the unlucky guys who missed this round because of the prepone. I came online just to find that the contest has already started... Perhaps changing the date might be a better idea than preponing in such short notice?

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

What the hell....I missed this contest :(

Didn't even received a mail about time change.

congratulations to all who will get positive delta due to this time change, not in my wildest thought had I even thought this way of improving rating. I hear "CHECKMATE" from admin.

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

    I literally did AB first and ate dinner then do C later only because of the time change TT. If it wasn't for the time change then maybe i could finish C quick enough:(

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

      I don't know bro. Maybe we need to practice for these time changes as well here.

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

Why is Codeforces such busy today? Even m1,m2,m3 are sometimes busy. But this contest is surely pretty good.

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

Someone solved E in 3 min. That is insane

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

It was a nice contest. i am waiting for a day when i will be able to solve div2 D.

is there anyone who can tell me how to approach problem D?

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    2 years ago, # ^ |
    ← Rev. 3   Vote: I like it +7 Vote: I do not like it

    I used two pointers approach.

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

      This is what i was thinking during the whole contest.

      But wasn't able to implement it.

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

        My solution lacks the optimization to not recalculate the whole route from k to the last l I checked, so it TLE's, but the idea in general is the same, so my implementation isn't correct either. welps

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

      Alex.Svanidze I did something similar but didn't TLE. I didn't submit it in the contest thinking it'll TLE. 173232461

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

        I guess me updating the values to zero changed it? lol, dunno, didn't really dive into your code, it looks quite similar, but there might be a significant one-liner difference

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

        Looking at it now, there is a huge difference. You check for the left and right separately, for just once. I go with loops until I reach a non-valid point. If the testcase needs to run on zig-zag, I will recalculate the whole segment between l-r and my solution will go up to n^2, yours will never exceed linear imo.

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

          I'm not quite sure whether it'll exceed linear or not. But if I'll divide the slimes into groups as mentioned in the editorial then I can be sure that it'll be linear because we on 2 checks at least one pointer will move, if it'll not move then it's impossible. There is no overhead of reiterating on the already seen indices. But in case of my solution without groups we are reiterating on some sets on points again and again.

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

How to solve E?

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

    I solved it like this. I'm not entirely sure why this worked. 173206034

    Edit: See Shisuko's post below. That's why this worked.

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    2 years ago, # ^ |
    ← Rev. 2   Vote: I like it +33 Vote: I do not like it

    For this proof, we assume that the matrix is $$$0$$$-indexed, i.e. $$$0 \leq r < n$$$ and $$$0 \leq c < n$$$. Also, note that this is exactly the same as OleschY's solution shown above with the really nice visual diagram. So just read this if you're interested in a proof of correctness haha

    Note that the condition is equivalent to saying a[r1][c1] - a[r1][c2] != a[r2][c1] - a[r2][c2] (mod n). Let d_{c1, c2}(r) = (a[r][c1] - a[r][c2]) mod n; for a fixed (c1, c2), we want d_{c1, c2} to be distinct for different input values of r. But now we can see that we are very limited---there are n possible values of r, but also n possible different outputs of the function. So we want this d_{c1, c2} to be some permutation of 0 to n-1.

    Let's set the matrix such that a[r][c] - a[r][c+1] = r always holds. Then, note that this implies (by induction or whatever) that d_{c1, c2}(r) = (c2 - c1) * r mod n. But if (c1, c2) are fixed, then (c2 - c1) is just some nonzero constant, and because n is prime, we know that d: r -> kr mod n is a permutation for any nonzero k.

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

In problem C, why can't we just choose k=1 every time? S must contain a number multiple of k=1 and this/any number can therefore be removed with cost k=1.

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

    You are required to remove the smallest multiple.

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

    u can only remove smallest multiple of k.So if 2 is there in T then if u select 1 twice then the second time 2 will also be removed.Which is wrong.

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

      Thank you! So we can just delete all multiples up-to a multiple that is in the target T. example if S={1,2,3,4} T={3} with k=1 we can delete just {1,2} because the smallest multiple remaining is 3 and that has to stay in T.

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

    what if lowest multiple of 1 needs to remain?

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

    you delete smallest multiple of K present in S.

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2 years ago, # |
← Rev. 3   Vote: I like it +22 Vote: I do not like it

Problem D has the same idea with Circle Eating in Codechef. But in codechef contest, only 8 people get AC in contest, otherwise there are over one thousand people pass pretests in Codeforces Contest! It's amazing.

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

    How to solve D?

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

      If I don't misunderstand the meaning of problem, you can see the editorial in Codechef to get the main idea.

      P.S. update the link of editorial. P.S.2 it seam the solution of the two problems are quite different...

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

        Editorial is a Pro feature now on Codechef............

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    2 years ago, # ^ |
      Vote: I like it -36 Vote: I do not like it

    This contest should be unrated!

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

Thank you so much for problem E! I (don't) wish you good health, love, high esteem and respect from loved ones, achieving your dreams to infinity, happy life, have magical moments and memories, and obtain what you really want, because that is the only way to fulfillment, realization and happiness!

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

Why is My Submission to D failing test case 10 :( . Can anyone explain? Thank you!

Code : 173206067

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

I don't know why Codeforces is really laggy today, even m1.codeforces. By the way, can somebody tell me a case where I got the wrong answer on Problem D. I got WA on 3rd pretest. Thanks alot <3 <3 <3 Here is my submission: 173222229

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

    Try this test:

    1

    5 3

    -3 -3 5 -5 1

    It should give "YES", but your code gave "NO"

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

Why my code of problem D wrong answer on Test #3? Can someone tell me? Thanks!

173220801

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

    try this case 1 5 4 1 200 -100 1 -100

    the answer should be NO, but your code gave YES

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2 years ago, # |
  Vote: I like it +42 Vote: I do not like it

Dear MikeMirzayanov, Why are we penalized with a -50 for resubmission when the site goes down? I got -150 due to unwanted resubmission when the site went down.

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

    Same here, I have submitted 4 exactly identical codes due to CF lagging and got -150 for that.

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

    Same with me !!

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

    Same, although I've submitted identical codes, I got -100.

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

Can anyone give me a failing case for https://mirror.codeforces.com/contest/1734/submission/173197473

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

Good round but I didn't manage to write D:( can someone please give the failing testcase? I will be glad if someone could help me

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

Dumbass me trying to use Fenwick tree for D...

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

Because of the Website issues, In problem B the same code got judged twice and I got -100 so is there any solution or anyone got the same problem? 173177338

173176654

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    2 years ago, # ^ |
      Vote: I like it +11 Vote: I do not like it

    Yes, I faced the same issue while submitting solution for problem A. it got submitted twice.

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

    Same, i got -150 for unwanted resubmission of B.

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

    I faced the same thing while submitting a I got 8 WA in 1 second.

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

      sad:'( I hope this issue will be solved ISA

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

i've done the solution for D and it passed the sample tests but i ran out of time and couldn't submit , i hope it gets WA after the system tests because i'd be so mad if it got AC

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

    How you did C ?

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

      it is the same idea of sieve of eratosthenes , iterate over the string and if the current number (let it be num) needs to be deleted the the i should iterate over the multiples of that number (let it be j) and take the minimum cost to delete that j which is min(mnCost[j] , num) i should break when j is multiple of num but j cannot be deleted from the set as i won't be able to do this deleting operation using this num in the future look at my code for more clarification

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

        It feels like C was much easier than B, it was so direct question...

        I felt like some data in B was missing they should have mentioned if the current room where we have reached is having torch than it will be counted too.

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          2 years ago, # ^ |
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          Yes it should have been mentioned, but you just have to see the test case and you will understand that the room is counted too

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

https://youtu.be/bOizr3O0elA

This channel posted correct solutions of A & B during the contest and many participants would have seen this. Due to this, the rankings would be skewed and would lead to an unfair contest, please do something regarding this.

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

    Plag check wouldn't be reliable in problem A & B to eliminate those who copied either. Probably making it unrated should be considered as those videos have 500+ views.

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

      Eh bad for you that the video was published after the contest

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

estimated rating of C?

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

    maybe 1100-1300

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      2 years ago, # ^ |
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      understandable, did u know why your E works before submitting?

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

        Nah, I do not have proof of why it works, I am not sure, even now why it is working

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          2 years ago, # ^ |
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          then how did it strike u that that could be the solution lol?

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            2 years ago, # ^ |
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            Actually i dry run this on sample test cases and it is working fine, but I do not have the exact idea why it works for every test case. it is a kind of hit and trial.

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

Can this submission for problem F be hacked?

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

I am a shit and I didn't solve C,though C is very easy.

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

This Ame-wiki guy were in my room-213..

when I was going to see his/her code at contest time. I was shocked!! Just try to unserstand what those line indicate.... Submissions are:

1734A

1734B

1734C

1734E

I think to makes code unreadable to others is nothing but scam..

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2 years ago, # |
  Vote: I like it -47 Vote: I do not like it

I get very angry because of the time of this round.

I turned on my computer at 22:15(utc+8) and it is already over.

It's a good idea to put off it. But U chose to make it earlier. That's one of the worst decisions U can make.

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    2 years ago, # ^ |
      Vote: I like it -18 Vote: I do not like it

    it's unrated for you, what's your problem?!

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

      It doesn't matter. I don't care whether it is rated. I only want to enjoy the process of competing. But I can't today.

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        2 years ago, # ^ |
          Vote: I like it -13 Vote: I do not like it

        There's an option which is virtual participation, You can do it any time in the year !!!!!!

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

    I thought someone would comfort me. But just downvotes.

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2 years ago, # |
← Rev. 2   Vote: I like it -45 Vote: I do not like it

:/

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

    Well you also cheated in D so why are you so angry?

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

    So you cheated in this round Right? If so you have no qualification to complain it bro（I just think your code of D is very suspicious,if you didn't,I'm sorry.)

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2 years ago, # |
  Vote: I like it +14 Vote: I do not like it

nice problems! orz arvindf232, AHappyPotato and __jk__

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

why the fuck am I missing D by an inch every single contest !!!

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

    same. I didn't submit my D in contest thinking it'll TLE, now submitting the same gave me AC.

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2 years ago, # |
  Vote: I like it +10 Vote: I do not like it

May I ask why the data range of problem C is $$$10 ^ 6$$$, but $$$O(N \sqrt{N})$$$ time complexity can pass? I can't understand it.

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2 years ago, # |
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Why did this brute force code get AC after the system test? Is it wrong or right?

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    2 years ago, # ^ |
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    I don't think that is brute force cuz it's pretty same as my code and I can prove it :vv

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      2 years ago, # ^ |
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      I optimized this code and proved the new one was right, so I think this is brute force. So how to prove this code is right? Thanks a lot.

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        2 years ago, # ^ |
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        The code is way too long and complicated so I just view it fast and get the main idea (hope it not gone wrong :vv)

        Just start from k and then go left until got a better choice than the current then update to that point, if it invalid then do the same to the right and if it invalid then print no otherwise if get to 0 or n + 1 then yes

        (Sorry for my bad English and knowledge :<<)

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          2 years ago, # ^ |
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          Oh, I know its correctness, but I wonder if it's time complexity is right (Why didn't it get TLE?).

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            2 years ago, # ^ |
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            Because you start at k and then go for a better choice, if it exist on the left then update if not check the right and update (pretty same as 2 pointers but instead of pointing from the outer to k now we spread from k to the outer) so the time complexity is just O(n)

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              2 years ago, # ^ |
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              But while it go to the left, the right also cost time. If there is a situation that every time it go to the left one step and need to check the right in $$$\mathcal O(n)$$$ time, it will cost $$$\mathcal O(n^2)$$$ time.

              (Sorry to my poor English)

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2 years ago, # |
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How can I view the 2839th token of problem D test 3?

Or could someone tell me where's wrong in my solution :(

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

    keep track of each testcase and print the respective testcase in string.

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

Why my code of problem D wrong answer on Test #3 [60th token] ? Can someone tell me? Thanks! https://mirror.codeforces.com/contest/1734/submission/173229017

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

Can Someone explain me the time complexity of problem C? What will be the expression in big O notation?

I thought it will give TLE but it didn't ╰(*°▽°*)╯

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

Problem D video Editorial

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2 years ago, # |
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Estimated rating of D anyone?

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2 years ago, # |
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I didn't play well in this contest, so I hope I can cheer up in the next consest. ^_^

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

I’m leavin' my name here 'cause it’s the first contest I participated in. And I even got a rating rise!

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2 years ago, # |
← Rev. 2   Vote: I like it +60 Vote: I do not like it

Is it confirmed that GOI_Official is an individual participant? I find it quite incredible that they solved ABCDE all within a span of fifteen minutes. This includes a submission at 9m12s for D (WA test 3), followed by the first submission for C at 9m50s (AC) and then a second submission for D (AC) at 10m41s. This really gives me the impression that it likely involved at least two programmers coding in parallel.

There is also a slight inconsistency in their submission formatting. Submissions for A and D (173165060 173171017 173172113) include a header with the problem names and links, but these are missing in the submissions for B, C, E, and F (173169227 173171420 173175699 173185632). All submissions have the following two lines:

//author: wuge with noi2022 cu
//https://www.luogu.com.cn/team/48234

I would guess that noi2022 refers to a National Olympiad of Informatics (CU might be the institution?), which generally involves a team (wuge might be the team name?), and the link below (which seems to be inaccessible in my region) has "team" in its url.

If it is the case that this user is actually representing a team, where different members of the team were able to code in parallel, I don't think this is within contest regulations (which required the user to register "as an individual participant"), so they should not be included in the official standings then. Of course, I don't know for sure that the user represents a team, but I think this should be investigated.

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    2 years ago, # ^ |
      Vote: I like it +22 Vote: I do not like it

    In fact Wuge seems to be a CPer's name,And in NOI2022,he actually got the bronze medal.

    I agree on your guessing,I think two CPers worked together,and one solved AD,another solved BCEF.

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

    U R probably right. It's imposisible to code at such a speed.

    They may share something, including read() and main() and the name of function meyi(). But A&D have a header. That is different. The time is also strange.

    GOI is a team. They hold a contest in luogu(a famous OJ in China), and it turned out to be a mess.

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    2 years ago, # ^ |
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    Luogu is an OJ in China, and that url is a team of it.NOI is the Olympaid contest of China (Its whole appellation is National Olympaid in Informatics.) and cu is the symbol of copper, it means copper medal.

    That code and the time is quite strange, but the code mentioned a code editor called CP editor. There are also some strange variable names like shaya and wugecu. They look like Chinese Pinyin. Is that the editor's feature?

    Also, CP means couple. So is CP editor an editor that allow two persons code together? I think it is NOT individual, too.

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2 years ago, # |
  Vote: I like it +10 Vote: I do not like it

Why do we care for codechef:(

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

Why not unrated?

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

asghar dar kamin ast!!!!! asghar is lurking!!!!!! Асгар в бегах!!!!!!

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