Ari's blog

Codeforces Global Round 9
By Ari, 3 years ago, In English

Hi!

On Jul/04/2020 17:45 (Moscow time) we will host Codeforces Global Round 9.

It is the third round of a 2020 series of Codeforces Global Rounds. The rounds are open and rated for everybody.

The prizes for this round:

  • 30 best participants get a t-shirt.
  • 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2020:

  • In each round top-100 participants get points according to the table.
  • The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
  • The best 20 participants over all series get sweatshirts and place certificates.

Thanks to XTX, which in 2020 supported the global rounds initiative!

The problems of this round were prepared by a team of authors: adamant, antontrygubO_o, Ari, dengyaotriangle, hugopm, Kuroni, enoone, and Ynoi. We would like to thank the following people:

You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :)

To save testers the work of writing their opinion in the comments, we have compiled some of their opinions for them!

Round Feedback

Good luck!

UPD: Score distribution:

500 — 750 — 1500 — 1750 — 2000 — 2000 — 2250 — 2750 — 4000

UPD2: Editorial

UPD3: System tests have finished, congratulations to the winners!

  1. tourist
  2. scott_wu
  3. yosupo
  4. Um_nik
  5. fantasy
  6. lqs2015
  7. heno239
  8. Motarack
  9. zeronumber
  10. Itst_boyfriend
Announcement of Codeforces Global Round 9
 
 
 
 
  • Vote: I like it
  • +2693
  • Vote: I do not like it

Comments Comments (449)
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3 years ago, # |
  Vote: I like it +3388 Vote: I do not like it

As a tester, give me contribution.

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    3 years ago, # ^ |
      Vote: I like it +49 Vote: I do not like it

    You are so honest. Otherwise, most of time tester tries to gain contributions by just commenting something shit....

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    3 years ago, # ^ |
      Vote: I like it +177 Vote: I do not like it

    The only thing I remember about Monogon is that his first ever contest after being such a beauty was ruined due to long queues and finally the round became unrated. Awaiting another round from you.

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

    ok

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    3 years ago, # ^ |
    ← Rev. 2   Vote: I like it -16 Vote: I do not like it

    Sorry for that..

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    3 years ago, # ^ |
      Vote: I like it +26 Vote: I do not like it

    You are now in top 10 contributors. Cong!!

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    3 years ago, # ^ |
      Vote: I like it +29 Vote: I do not like it

    may be for the first time a tester is going to get more contribution than the setter xd
    need 247 more only :P

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    3 years ago, # ^ |
      Vote: I like it +30 Vote: I do not like it

    The most upvoted comment ever?

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

    If only herd immunity was as easy as herd behaviour...... P.S. you have my vote.....

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

    I hope Monogon prepares a round after gaining such support from the community. We will try to make the contest announcement blog the most upvoted blog on CF.

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

    You have it, >2000 upvotes :D.

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    3 years ago, # ^ |
      Vote: I like it +251 Vote: I do not like it

    As the most upvoted comment in history, I think this proves that the greedy works.

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

    Damn! Even, most of the "contest announcement" blogs have less upvotes.

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

    Would it break the tourist's global round 5 record?

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

    This has to be a record of some kind.

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

    Can monogon's comment beat tourist's rating someday? =O

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3 years ago, # |
  Vote: I like it +125 Vote: I do not like it

AC Round #3

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

    What is AC Round ?

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      3 years ago, # ^ |
        Vote: I like it +94 Vote: I do not like it

      AC is a discord server for competitive programmers. Most of the authors/testers of this round are members of the server. This is the third round made by AC members, here and here are the first two rounds.

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3 years ago, # |
  Vote: I like it +208 Vote: I do not like it

This has to be one of the best contest announcement.

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3 years ago, # |
  Vote: I like it +25 Vote: I do not like it

I am not tester, but i strictly reccomend you to participate in this contest!

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3 years ago, # |
  Vote: I like it -60 Vote: I do not like it

I'm a tester, and this round is very good.

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

    Why am I getting downvoted? I'm stating my opinions as a tester.

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

      Cause everyone saw that, you are not in the tester list :v

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3 years ago, # |
  Vote: I like it +119 Vote: I do not like it

As a participant, I need more time to recover from the previous contest.

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3 years ago, # |
  Vote: I like it +304 Vote: I do not like it

They stole my contribution =(.

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

Ok then

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

very comedically humorous Ari

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3 years ago, # |
  Vote: I like it +39 Vote: I do not like it

Is feedback meant for frightening us?

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3 years ago, # |
  Vote: I like it +48 Vote: I do not like it

As a participant, I am already scared

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3 years ago, # |
← Rev. 2   Vote: I like it +204 Vote: I do not like it

Finally this day has came, a round with adamant as an author.

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

thanks for the meme!

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

The announcement just ensured that one more time we are gonna miss MiFaFaOvO vs tourist match.

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

    Tbh, it looks more like ecnerwala vs tourist to me. Just an opinion tho.

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      3 years ago, # ^ |
        Vote: I like it -19 Vote: I do not like it

      I don't get why you guys are more interested in tourist than yourself.

      Is that why you are green/cyan?

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

        I find inspirations seeing the success of some great coders so that i am interested about them.You better focus on your own success (as you are a colorless or a fake account).

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3 years ago, # |
  Vote: I like it -24 Vote: I do not like it

Glad a real CF round is coming,last round killed my spirit...

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    3 years ago, # ^ |
      Vote: I like it -52 Vote: I do not like it

    Hope this doesn't happen

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

      .

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

        Do you want to say anthing about this

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

          Yes I wasted a lot of time and truly it sucks . Moreover it made me realized that I should focus on solving problems instead of making memes. I had no intention of disrespecting you but only making letting you know about my mistake.

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

            Thanks for letting me know. I had no intention of disrespecting you too.

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

As a participant, I am eager for tourist vs Um-Nik

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

    That's rather as a spectator. You don't need to participate for that.

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

tags: "doomsday" oof

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3 years ago, # |
  Vote: I like it +12 Vote: I do not like it

People trying to be sarcastic in comment section Problem Setters And Testers : Say No More

Ps : Is it best announcement ever? :P

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3 years ago, # |
  Vote: I like it +116 Vote: I do not like it

amiya : " I'm happy sitting atop the CF rankings. You guys give the contest."

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3 years ago, # |
← Rev. 3   Vote: I like it +69 Vote: I do not like it

You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :)

Is this statement meaningful or is this general good advice for any round?

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3 years ago, # |
  Vote: I like it +139 Vote: I do not like it

But man, by the time I understand 9 problem statements, 2,5 hour is already gone, and I already forgot 8 of them...

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

As a russian guy, I don't understand tester's feedback.

Joke

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3 years ago, # |
  Vote: I like it -27 Vote: I do not like it

Looks like it's going to be a difficult contest.

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3 years ago, # |
  Vote: I like it +220 Vote: I do not like it

"As a problemsetter, I am sorry"
As a contestant,

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3 years ago, # |
  Vote: I like it +256 Vote: I do not like it

......

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

As a participant, I will participate.

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

Looking forward to the problems. The announcement is hilarious and I hope the problems will be as well.

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3 years ago, # |
  Vote: I like it +235 Vote: I do not like it

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3 years ago, # |
← Rev. 2   Vote: I like it +21 Vote: I do not like it

Don't worry, you guys are gonna enjoy the round :)

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3 years ago, # |
  Vote: I like it +19 Vote: I do not like it

Probably, one of the best contest announcements.

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3 years ago, # |
← Rev. 4   Vote: I like it -11 Vote: I do not like it

As a contestant, I quit.

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

i'm confused, should we be playing or not?

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3 years ago, # |
  Vote: I like it +185 Vote: I do not like it

I see that I'm going to love this round...

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    3 years ago, # ^ |
      Vote: I like it +94 Vote: I do not like it

    No, you'll say that there is another platform for such contests

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      3 years ago, # ^ |
        Vote: I like it +106 Vote: I do not like it

      To be honest, adamant and antontrygubO_o together as problemsetters give hope that we'll finally see some balance.

      But also the opposite is possible: that every problemsetter has just a position (A-I) assigned and all the problems will be chosen completely independently from the others and we'll finish having a 100% "another platform" contest.

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

Hoping to become an Expert after this round :)

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3 years ago, # |
  Vote: I like it +441 Vote: I do not like it

Do you want to get fewer participants with this anti-advertising of the problem set? If the goal is to avoid the server load, just say that there will be a lot of math in div2 problems.

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    3 years ago, # ^ |
      Vote: I like it -15 Vote: I do not like it

    LOL ! People will still try out of courage and for rating ! If it goes well they will be commenting like Best ProblemSet ever ! and if not they have their cliche MathForces

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    3 years ago, # ^ |
      Vote: I like it +431 Vote: I do not like it

    There are a lot of math in div2 problems.

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

    Errichto It's been a long time since we saw you setting problems ! Come Back ! Soon ! :)

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    3 years ago, # ^ |
      Vote: I like it +35 Vote: I do not like it

    Even better, just say the whole round is Geometry

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    3 years ago, # ^ |
    ← Rev. 2   Vote: I like it -16 Vote: I do not like it

    When you khow people scared with math then do you do something like tutorial on how to get well in math? Errichto

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

      I doubt that abundance of tutorials is going to cure aversion to "math".

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    3 years ago, # ^ |
      Vote: I like it -14 Vote: I do not like it

    I think. they r going for reverse psychology here....!!

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

First time, I see meme in contest announcement.There must be a reason behind it. We should be aware of that.Good luck to everyone. :p

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3 years ago, # |
  Vote: I like it -34 Vote: I do not like it

How pupils become tester? :D

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3 years ago, # |
  Vote: I like it +34 Vote: I do not like it

As a contestent, I want rating.

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

xd

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

Same story, again and again, my smoll pp skills and big pp problems.

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

Best CF Round invitation ever =P

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

as a participant, i am also scared and i don't want to participate!)

GL&HF to everyone!!!

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

....

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

    As a tester, My advice is to think 1 more day, because problems are more scarier than you are thinking...XD

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

I don't know why but it is giving me vibes of an amazing round.

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3 years ago, # |
  Vote: I like it +167 Vote: I do not like it

.PicsArt_07-02-02.16.38.jpg****

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3 years ago, # |
  Vote: I like it +7 Vote: I do not like it

9 Problems with an army of testers and 8 writers. Excited

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3 years ago, # |
  Vote: I like it -27 Vote: I do not like it

IT IS TAGGED DOOMSDAY!!!

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

New here, it is going be my first Global Round and the comments already scare me. Is it a good idea for a new guy to take part in it? or will it be discouraging?

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

    If you are new dont think of rating from the beginning try giving as many contest as you can. Thats what i learnt

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3 years ago, # |
  Vote: I like it +12 Vote: I do not like it

9 problem that's huge. I appreciate the hard work to make a contest.

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

    Yes appreciate problem setters for these kind of contests

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      3 years ago, # ^ |
        Vote: I like it +41 Vote: I do not like it

      "You will be given 2 hours and 30 minutes to read all of them." I think that's what he is trying to say.

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3 years ago, # |
  Vote: I like it -41 Vote: I do not like it

Links of previous global rounds:

Codeforces Global Round 5

Codeforces Global Round 6

Codeforces Global Round 7

Codeforces Global Round 8

Hope this helps!

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

    Appreciate your work but we can directly search any round and go to contest link in the announcement.

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      3 years ago, # ^ |
        Vote: I like it -8 Vote: I do not like it

      The reason why it is not useful is probably not that "we can find it ourselves" but that this list was also shared in the previous global round. In fact, link to a web app was shared which can do this right away.

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3 years ago, # |
  Vote: I like it -16 Vote: I do not like it

This global round seems to be very special among all previous global rounds because of its awesome announcement!!

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

I was going to make a century of losing rating in last contest...I think,this is another opportunity to complete the century...Shouldn't I be happy!!! SENTY_EMO

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

how is global round different from other rounds???

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3 years ago, # |
  Vote: I like it +12 Vote: I do not like it

As a contestant, I will take part in the contest. :)

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3 years ago, # |
  Vote: I like it -16 Vote: I do not like it

Can someone tell me what happened to static a2oj? I used to solve problems from there difficulty wise and now, instead of that a different website with that names comes and all the problems of the ladder are locked there.

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

Finally, memes are on Contest announcement blog post :v

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3 years ago, # |
  Vote: I like it -11 Vote: I do not like it

Explain me the difference between Educational round and Global round in div 2 like contest there is time penalty what about Codeforces Global Round .Thank you.

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

    In Global round also every problem score decrease with time . It's almost like Div-2.

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    3 years ago, # ^ |
      Vote: I like it +24 Vote: I do not like it

    1. Global round is rated for everyone, educational round is rated for people who have rating less than 2100

    2. Global round has some fixed points for each problem which reduces slowly as time goes on, all problem has equal points on educational rounds.

    3. Hacking runs parallel with contest in global round, there is hacking phase in educational rounds after contest finished.

    4. Wrong submission on finally accepted solutions will cost you 20 points in global round, in educational rounds it will cost you additional 10 minutes time penalty.

    5. On global round last pretest passed solution will be judged and resubmission will cost you 50 point and in educational rounds all pretest passed(accepted) solution will be judged and 1st solution that passed system test will be considered.

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

      How do you compare 20 points vs 10 minutes of penalty? What is the exact relation (if there exists one)?

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

        I compare in sense of what will happen one submit a wrong solution.

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

thanks to all of them for frequent rounds

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3 years ago, # |
  Vote: I like it +7 Vote: I do not like it

Next round after the global round is one week later.Are we not going to have any round before that?

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    3 years ago, # ^ |
    ← Rev. 2   Vote: I like it +10 Vote: I do not like it

    There are almost 2 educational and div3 rounds in every month.So probably we will be having both also if a contest is added for date x it does not mean mike can not add a contest which has date strictly lesser than x.

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

A meme in the announcement .. you got my upvote

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    3 years ago, # ^ |
      Vote: I like it -8 Vote: I do not like it

    Hey Boss how to get like your meme idea.. I want to make my contribution 0.

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

      the idea just flashes in my mind and I search for photos that can present the meme and edit it on paint
      I can give you an advice some of my memes goes this way you just compare 2 completely opposite situations like this one
      it's how I used to be when I started and how I'm like now this meme is actually sad for me XD
      or like this one
      it starts with someone asking them to be quite while it ends up with a party so there should be an element of surprise if it's something expected or usual then this is a bad boring meme and it should be about codeforces and competitive programming not jokes about html that's out of the context

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3 years ago, # |
  Vote: I like it +179 Vote: I do not like it

You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :)

Problem I.

You are given two integers a and b. Print a+b.

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

I am excited for the round..hope for the best

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

dude that feedback gave me chill more than any meme xD xD

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3 years ago, # |
  Vote: I like it -24 Vote: I do not like it

WTH to me. i was going to attend the contest today at 20:35..

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3 years ago, # |
  Vote: I like it +87 Vote: I do not like it

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

I like this meme!

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

I love the announcement """""D

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3 years ago, # |
  Vote: I like it -48 Vote: I do not like it

In problem B,can anyone explain this formula => a+(a+1)+(a+2)+...+b=(a+b)∗(b−a+1)/2 and what is it called

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

I hope there are a few or no problems based only on observation

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    3 years ago, # ^ |
      Vote: I like it -26 Vote: I do not like it

    I hope a problemset like that of the previous round doesn't happen again. Problems A-D: Observation. A-C are 1 liners. D is two nested for loops which can be written with 3 lines. Problem F: Think for half a second, implement for half an hour.

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

In China, there is a well-known serie of huge datastructure problems called Ynoi.... Is it gonna have huge datastructures like ctholly tree?

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3 years ago, # |
  Vote: I like it +54 Vote: I do not like it

As a stupid American, I don't get the testers' jokes.

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3 years ago, # |
  Vote: I like it -21 Vote: I do not like it

As a participant, I have a hunch that I should hide my brain during the contest

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3 years ago, # |
  Vote: I like it -8 Vote: I do not like it

Excuse me. Can someone tell me how the round is rated? I mean: is it rated like div.1, div.2, or div.3? I'm not very familiar with the contests of CodeForces (as you can see I'm a Newbie). Thanks for helping!

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    3 years ago, # ^ |
    ← Rev. 3   Vote: I like it -20 Vote: I do not like it 
    Sorry for wrong...
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      3 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Alright. Actually I thought that it is rated in a way like div... but it seems that it's different. Thanks anyway.

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3 years ago, # |
  Vote: I like it -16 Vote: I do not like it

so here comes the DOOMSday

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

For the first time, I am feeling nervous that something bad is going to happen with me in this round :(

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

    and what are the good things that happened to you in any round till now

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

Codeforces contests are like a sport for me . I enjoy the problem mostly without noticing my rating .

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

is this one as easy as div 2?

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3 years ago, # |
  Vote: I like it -74 Vote: I do not like it

tourist after reading round feedback

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

As a participant, I am scared.

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

how the contribution is calculated.

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

    It works like the hippos, you have to effectively shed your territory.

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

Ari Hey, I understand that you want to make a point, but don't you think tagging them is unnecessary? I believe noone likes to be tagged just to see themself being thanked every week.

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

GOOD LUCK TO EVERYONE!!!

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3 years ago, # |
  Vote: I like it +19 Vote: I do not like it

Out of curiosity, What's the record for the most downvotes? (Can this comment break that record? xD)

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3 years ago, # |
  Vote: I like it +149 Vote: I do not like it

gamegame and dorijanlendvaj, for their help in improving the humor of the round.

During round :

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3 years ago, # |
  Vote: I like it +7 Vote: I do not like it

Honestly, Is this contest suitable for a newbie????

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    3 years ago, # ^ |
    ← Rev. 2   Vote: I like it -14 Vote: I do not like it

    Don't.

    tbh tho A and B solvable.

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

      Need to learn a lot. Couldn't solve even 1 ques. :(

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

        If you want easier problems to try on, i personally think the first few problems on AtCoder Beginner Contests are quite suitable. Have fun!

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

    Yes, AB should be easy enough. Go do it!

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3 years ago, # |
  Vote: I like it +194 Vote: I do not like it

10 minutes delay, sorry. I'm trying to fix Ruby installation.

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    3 years ago, # ^ |
      Vote: I like it +31 Vote: I do not like it

    No problem sir. Codeforces is such a good platform that these types of delays doesn't hurt if contest go on smoothly

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

    Contest smoothness >>>>> 10-15 minutes delay

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3 years ago, # |
  Vote: I like it +94 Vote: I do not like it

My adrenalin just got wasted

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

Delayed by 10 minutes :/

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3 years ago, # |
  Vote: I like it -264 Vote: I do not like it

What the fuck? Why is CF so bad in punctuality? -_-

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    3 years ago, # ^ |
      Vote: I like it +31 Vote: I do not like it

    you should write the words carefully.They are doing hardwork for us

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      3 years ago, # ^ |
        Vote: I like it -52 Vote: I do not like it

      Agreed but they can't just play with our time? Can they? :)

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        3 years ago, # ^ |
          Vote: I like it -17 Vote: I do not like it

        They don't force you to play this.. are they ?

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          3 years ago, # ^ |
            Vote: I like it -42 Vote: I do not like it

          Did someone force you to comment here? XD

          No hard feelings brother!

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

            Did someone force you to reply here?

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

              Did someone force you to make an entry? :3

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

        Try to compete in virtual contest then.

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

        Did codeforces questioned you ever ? or did they ever ask you to pay for such an amazing platform? Be patient.

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

          Tell me the day you need to pay to codechef or topcoder or any other site that exists!

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

            True, but be patient at the same time.

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

              Yeah bro absolutely! All the best to you for the round! Have a large delta!

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

            Someone is talking about codechef , LOL. Can you please deactivate your codeforces account? And enjoy codechef. All the best :)

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

              Can we deactivate it ? :/

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

            Do we need to state the difference in the quality of Codeforces and Codechef?

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

    A delay of 10 minutes is much better than an unrated contest or queueforces!

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

    Calm Down,man. We all are human, we all make mistakes.

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

    Don't thank MikeMirzayanov if you can't, But please don't hurt the sentiments of the fellow codeforces users.

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3 years ago, # |
  Vote: I like it +28 Vote: I do not like it

Oh shit! Now I'll have to listen to Twice once again.

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

    Oh shit! You had to listen Twice twice, it's two squared)

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

This ten minute extension is ruining the moment :(

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

my precious time....22:35->22:45

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

Delayed??

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3 years ago, # |
  Vote: I like it -8 Vote: I do not like it

Is today's contest suitable for newbie and lower pupil?

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    3 years ago, # ^ |
      Vote: I like it -8 Vote: I do not like it

    Yes...I think by solve a,b we can increase our rating easily !!

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

    A and B should be solvable by everyone, I think. But even if they weren't, participating in a contest is always suitable.

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

    Even if you couldn't solve any problem during the contest, you will learn something from the editorial afterward.

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3 years ago, # |
  Vote: I like it -49 Vote: I do not like it

What the fuck! Another 10 minute wasted. 10 min wasted before starting by waiting.

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

    Codeforces is doing hardwork for free. You should not say these 10min wasted. Its way much better than an unrated contest due to long queues.

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3 years ago, # |
  Vote: I like it -16 Vote: I do not like it

Ok, all set, 5.4.3.2.1 let's start..........not now, come again after 10 min xd

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3 years ago, # |
← Rev. 2   Vote: I like it -16 Vote: I do not like it

[deleted]

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3 years ago, # |
  Vote: I like it +52 Vote: I do not like it

An interesting observation: all the people complaining about adrenaline being washed out etc. are below blue and below.

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    3 years ago, # ^ |
      Vote: I like it +31 Vote: I do not like it

    Interesting observation: all the people always having problem about something and not taking a joke as a joke are purple and above

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

Codeforces Global Round Exists:

meme.jpg

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

As a contestant, I just read the questions

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3 years ago, # |
  Vote: I like it +12 Vote: I do not like it

This was the Hardest A i have seen till now.

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

    Not at all :| Hard but not hardest !!

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

      How can you tell me on my behalf.i said i have seen till now,read the comment again.

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

        Cause you attend 62 more contest..it is not so hard.

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

          I think i got horrified from the contest announcement.XD

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

    For me A was harder than B and C. Took me a while to reach the solution

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

      Same here solved A in total 1:30 hrs and C in 10 minutes. xD

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

        But C's logic was beautiful though, i was scared that am i missing some case here.

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3 years ago, # |
  Vote: I like it +12 Vote: I do not like it

As a tester, I am very happy that I can enjoy others suffering in the contest. This line become true lol. But really awesome problemset

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3 years ago, # |
  Vote: I like it +58 Vote: I do not like it

i should have taken those feedbacks seriously :(

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

Very good contest nice problemset

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

hope mifafaovo gets dethroned by umnik this time!

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

[*] rating

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3 years ago, # |
  Vote: I like it +138 Vote: I do not like it

As a participant, this round gave me PTSD. XD

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

    I gave this contest in the hope for specialist but it seems that still specialist is far away from me...

    BTW logic for 3rd one is

    "NO" if(a[0] > a[n-1] ) , else "YES"

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    3 years ago, # ^ |
      Vote: I like it +25 Vote: I do not like it

    I think I need more IQ to solve problem like these, not algorithm knowledge. :)

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

Arggg. Tough round. Great problems, though!

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3 years ago, # |
  Vote: I like it +161 Vote: I do not like it

Ari: how many constructive problems do we need?

Other setters: Yes

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

Great round with difficult problems. Hoping for a fast editorial.

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3 years ago, # |
  Vote: I like it +241 Vote: I do not like it

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

I wonder who did created problem D.

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3 years ago, # |
← Rev. 2   Vote: I like it +185 Vote: I do not like it


Never again.

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

    Thus, hocky went and made a catfish farm instead. He is now known as the catfish farmer.

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

Is there anyone else who could solve D in like 10-15 minutes and has no idea about solving C? Bad day!

Anyways how to solve C?

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

    The last element must be greater than the first

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

    how to solved D ?

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

    arr[0] < arr[n-1] => YES else NO

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

    if(a[n-1]>a[0]) cout<<"YES\n"; else cout<<"NO\n";

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

    if $$$a[0] < a[n - 1]$$$ then "YES" else "NO"

    Consider this example

    5 6 7 4 8 9 10 13 11 12

    This can be visiualize as

    $$$[increasing] [increasing] [increasing]$$$

    5 6 7 4 8 9 10 13 11 12

    But How we are breaking this sequence ?

    We are considering $$$first$$$ and $$$last$$$ will remain in the end of the process. So our focus is to remove all the element in between.

    See,

    4 $$$<$$$ 5 $$$(first element)$$$, this will insert break in our sequence, from this index we will start making new increasing sequence.

    Similarly observe, 13 < 12 $$$(last element)$$$, this will insert a breaking point.

    Now, if you think a little about it, you will see we can merging first increasing sequence and last increasing sequence like this

    5 6 7 4 8 9 10 13 11 12 ==> 5 6 7 4 11 12 ==> 5 6 7 11 12

    So the sufficient condition would be $$$a[0] < a[n - 1]$$$ for answer to be exists.

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    3 years ago, # ^ |
    ← Rev. 3   Vote: I like it +5 Vote: I do not like it

    34 people (and 2 in under the next such question) have replied to this comment but no one has even slightly explained why this is true. What's the use of such responses?

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      3 years ago, # ^ |
        Vote: I like it +52 Vote: I do not like it

      Many of them don't know. :p

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

      I proved it first before solving it. PLease Correct me If I go wrong any where. Let me explain the proof very clearly. if the minimum element of permutation that is '1' is last element of the array then plainly answer is No because no matter which ever operation you performed.the last 2 elements after operation will have minimum element that is '1' on RHS which means it is not possible to satisfy the condition that is a[i]<a[i+1].

      Now if 1 is in a[0] that is in first place then the answer is always "YES" , just converse of I said above.

      Now when '1' is in middle , things become nontrivial. For example 1 is in middle and after applying some sort of operation we reached a state where we have 3 elements and '1' lies in the middle of these elements , then lets say these elements are a 1 b.

      then if a<b then we can delete 1 from the middle and at the end we will have two elements a b since a < b then we can achieve a single element but when a > b we cannot.

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

    Observation 1: you can't make any operation that decreases the 1st element Observation 2: you can't make any operation that increases the last element If the 1st element is greater than the last elements, then in the best case you'll end up with 2 elements [a1 a2] where a1 > a2. Otherwise there is an easy method to eliminate all but 1 element.

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

    You have to remove the greater element in permutation while you can. If this element become the last in sequence, print YES, if you cannot remove the greater element, print NO. This is the key idea

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3 years ago, # |
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Can someone tell how to solve problem C?

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

    If v[1] > v[n] print "NO"

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

    Check if the first element is smaller than the last element

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3 years ago, # |
← Rev. 3   Vote: I like it +107 Vote: I do not like it

Problem setters and testers to all the participants rn:

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3 years ago, # |
← Rev. 4   Vote: I like it +21 Vote: I do not like it

G is a good problem for Div2D?

I guess a subsegment of the problems is reversed before the contest...

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

You will be given 2 hours and 30 minutes to solve 9 problems, and we highly encourage you to read all of them :)

Did they want us to suffer? There is no gap only between A and B, E and F

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

I really need to start thinking in multiple directions before coding. Had I done that I could have solved A much much earlier :(

Leason learnt.

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

Probably should've listened to the Round Feedback.

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

I am pretty much impressed that a trivial thing can be stated in such a difficult way (problem E).

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    3 years ago, # ^ |
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    I haven't done anything trivial in E.

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

    Imo the thing not THAT trivial either

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      3 years ago, # ^ |
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      I'm not saying solving this problem is trivial, of course. I can accept the opinion that the bubble sort might be non-trivial.

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3 years ago, # |
  Vote: I like it +91 Vote: I do not like it

Why did you put the easiest problem as G?

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

E killed my will to live, how to solve that?

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

    Transform the array into a permutation by considering pairs ($$$a_i,i$$$). Use bubble sort on the inverse of that permutation; each swap of elements which differ by 1 only remove that inversion.

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    3 years ago, # ^ |
      Vote: I like it +35 Vote: I do not like it

    In a non-sorted permutation there is always a pair of consecutive numbers which are in wrong order. You can swap them and it doesn't affect any other inversion.

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

      I tried to implement this for like an hour or more :/ Need to study the solutions.

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

        Hi, I'm still a little confused with the statement that "it doesn't affect any other inversion".

        In eg: 3 1 2, when we swap (3,2) we get 2 1 3, but here we created a new inversion (2,1).

        Can someone explain this please? Thanks.

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

          With 3 1 2 there are two inversions. Positions (1,2) and (1,3). We swap (1,3) because of the min diff of those two inversions. Then we swap the other inversion (position 1 and 2) resulting in 1 2 3.

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

            Why can't we perform swap of positions (1,2) and then (2,3). The value array will transform as follows : 3 1 2 -> 1 3 2 -> 1 2 3

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

              No. 3 1 2 swap positions (1,2) -> 1 3 2 swap positions (1,3) -> 2 3 1

              Note that we do not swap "the positions of..." or something like this. We swap the positions as given in the inversions.

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