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antontrygubO_o's blog

By antontrygubO_o, 22 months ago, In English

We will hold Codeforces Round 794 (Div. 1) and Codeforces Round 794 (Div. 2).

The point values will be:

Div2: 500 — 1000 — 1500 — 2000 — 2500 — 2500

Div1: 500 — 1000 — 1500 — (1500 + 1500) — 3500

We are looking forward to your participation!

UPD 1: Thanks to NEAR for supporting this round, details can be found in this post.

UPD 2: Editorial

UPD 3: Congratulations to winners!

Div1:

1. Rewinding

2. jiangly

3. ecnerwala

4. gamegame

5. maroonrk

Div2:

1. lmqzzz

2. Teating_

3. lunchbox

4. Nida1097

5. demacia

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

| Write comment?
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22 months ago, # |
  Vote: I like it +250 Vote: I do not like it

As VIP tester, good luck to all east Asians competiting until 4am

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    22 months ago, # ^ |
      Vote: I like it +118 Vote: I do not like it

    As a Japanese, when the contest ends the sun will rise... (btw why so late unusual time?)

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      22 months ago, # ^ |
        Vote: I like it +12 Vote: I do not like it

      I think it is to prevent clashing with codechef starters 40 which is from 10:30pm — 1:30am GMT +8

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        22 months ago, # ^ |
          Vote: I like it +97 Vote: I do not like it

        You are right. And we think that it's generally not bad to have a late time round once in a while (for people from other time zones).

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          22 months ago, # ^ |
            Vote: I like it +92 Vote: I do not like it

          why is it necessary to care about codechef?

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            22 months ago, # ^ |
              Vote: I like it +31 Vote: I do not like it

            Maybe because he is a problem admin at Codechef

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            22 months ago, # ^ |
              Vote: I like it +123 Vote: I do not like it

            Because Codechef is a good platform with good problems

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              22 months ago, # ^ |
                Vote: I like it +45 Vote: I do not like it

              Noice!!

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              22 months ago, # ^ |
                Vote: I like it +61 Vote: I do not like it

              Yeah, but sadly no one recognizes it.

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

              The only drawback is their bad plagiarism checker. Ratings of the fair contestants drop because of the massive cheater base and their plagiarism checker failing to detect them. But their problems are noice no doubt.

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              22 months ago, # ^ |
              Rev. 2   Vote: I like it +20 Vote: I do not like it

              Me: "I'm going to propose $$$20$$$ problems on Codechef."

              antontrygubO_o: "Codechef is not a rubbish bin!"

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                22 months ago, # ^ |
                  Vote: I like it +11 Vote: I do not like it

                Harder problems on codechef like medium/medium-hard are quality problems in general. I don't think you can so easily throw $$$20$$$ mediums to the so-called "rubbish-bin".

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                  22 months ago, # ^ |
                    Vote: I like it +16 Vote: I do not like it

                  In fact, I have proposed no medium/medium-hard problems.

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              22 months ago, # ^ |
                Vote: I like it +59 Vote: I do not like it

              With good loyal employees

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            22 months ago, # ^ |
              Vote: I like it +11 Vote: I do not like it

            even that is down now during the contest

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          22 months ago, # ^ |
            Vote: I like it +23 Vote: I do not like it

          Does that mean that there won't be any contests on cf(even if div1) at usual time or close to that on Wednesday?(since CC starters is held every Wednesday)

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            22 months ago, # ^ |
            Rev. 3   Vote: I like it +73 Vote: I do not like it

            also the point is that if time clashes it makes more sense to change the time of cc contest rather than cf contest because certainly cf is a better platform than cc with larger amount of interested participants

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              22 months ago, # ^ |
                Vote: I like it -45 Vote: I do not like it

              funny to see cyan judging which site is better, when he can't even solve medium level problems on any of the sites.

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                22 months ago, # ^ |
                  Vote: I like it +105 Vote: I do not like it

                Funny to see low-rated expert judging cyan with 50 rating difference between them.

                TimDee

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                  22 months ago, # ^ |
                    Vote: I like it +25 Vote: I do not like it

                  that's why I didn't said anything about website like which website has better problems :)

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                  22 months ago, # ^ |
                    Vote: I like it -17 Vote: I do not like it

                  I think you have weakness in reading texts,I said better platform not better problems

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                  22 months ago, # ^ |
                    Vote: I like it +9 Vote: I do not like it

                  it should be better if we do debate in dm instead of spamming announcement blog xD. Also what is the other thing in coding platforms other than problems, As much as I recall it was long ago when codechef contest goes unrated!

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                  22 months ago, # ^ |
                    Vote: I like it +11 Vote: I do not like it

                  oh okk,try visiting cc now then

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                22 months ago, # ^ |
                Rev. 5   Vote: I like it -17 Vote: I do not like it

                If I am an asshole in problem solving ,you are as asshole as me ,our rating difference is 55...also you may never reach things in future that I will do + it doesn't require to be red to understand which platform is better,,,also If I can't solve medium level prblms ,you can't also, it's funny to see someone who is just above 1600 out of nowhere insulting someone who is just few ratings less than him

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                  22 months ago, # ^ |
                    Vote: I like it -10 Vote: I do not like it

                  I never said I am better than you :)

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

                  I don't think being higher rated ( no matter the difference ) allows you to insult anyone.

                  -- A non-alt account.

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                  22 months ago, # ^ |
                  Rev. 2   Vote: I like it -30 Vote: I do not like it

                  Fuck you, shut up, gitgud

                  Marinush

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                  22 months ago, # ^ |
                  Rev. 2   Vote: I like it -28 Vote: I do not like it

                  Success makes so many people hate you. I wish it wasn't that way. It would be wonderful to enjoy success without seeing envy in the eyes of those around you.

                  bleahbleah

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                  22 months ago, # ^ |
                    Vote: I like it -8 Vote: I do not like it

                  Learn how to troll with getting upvotes

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                  22 months ago, # ^ |
                    Vote: I like it -7 Vote: I do not like it

                  Thanks for the advice rotavirus :)

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          22 months ago, # ^ |
            Vote: I like it +6 Vote: I do not like it

          Two back to back contests

          Two back to back contests!!
          :)
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          22 months ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          That is right! Just like sometime there are round which is from 17:35 — 19:50 GMT+8.

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

        turns out badly, the CodeChef servers are down

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

        codechef keeps contest according to codeforces (it is much smaller)...(see now contest is postponed..)

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

      Land of the Rising Sun

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

    why so late

    ⚫⁔⚫

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    22 months ago, # ^ |
      Vote: I like it -6 Vote: I do not like it

    Bro I hacked someone on C.

    but there are other people also , who will get WA on C due to that testcase.

    When will they rejudge.

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

Amazing Unusual Time

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22 months ago, # |
Rev. 2   Vote: I like it +26 Vote: I do not like it

As a tester and an Anton-problem-enjoyer, I can confirm that the problems are very beautiful. I'd say some of the problems are probably the best I've seen this year, but I won't jinx the round by saying that

Spoiler
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    22 months ago, # ^ |
      Vote: I like it +45 Vote: I do not like it

    Nice

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    22 months ago, # ^ |
      Vote: I like it -6 Vote: I do not like it

    Bro i hacked somenone on C

    when will other people get testted on that testcase for C problem.

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22 months ago, # |
  Vote: I like it +70 Vote: I do not like it

:o atcoder announcement format

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

Div2: 500 — 1000 — 1500 — 2000 — 2500 — 2500

Div1: 500 — 1000 — 1500 — (1500 + 1500) — 3500

The last two Div2 tasks are worth the same, but there aren't two tasks in Div1 that are worth the same.

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    22 months ago, # ^ |
      Vote: I like it +77 Vote: I do not like it

    The last problem in Div2 will be the first subtask of the fourth problem in Div1.

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22 months ago, # |
  Vote: I like it +110 Vote: I do not like it

Thanks to antontrygubO_o for rejecting all of the problems of himself for creating this contest.

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22 months ago, # |
  Vote: I like it +26 Vote: I do not like it

It's really an unusual time, so I can't attend :( hope others enjoy it

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22 months ago, # |
  Vote: I like it +11 Vote: I do not like it

WOW!, Contest Announcement itself is neat, clean and precise. Looking forward for my first MIDNIGHT contest

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22 months ago, # |
  Vote: I like it +31 Vote: I do not like it

I finally get a excuse to wake up till 1 in the night for actual reasons

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22 months ago, # |
  Vote: I like it +45 Vote: I do not like it

"Rated range: (−∞,1899] for Div2, [1900,∞) for Div1", means "Rated range: (−∞,1899] for Div2, [1900,tourist] for Div1"?

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22 months ago, # |
Rev. 2   Vote: I like it +33 Vote: I do not like it

.

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22 months ago, # |
  Vote: I like it -19 Vote: I do not like it

very unusual time

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

All hail our emperor anton

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

Unusual start time: Thursday, May 26, 2022 at 01:35UTC+8

Aha

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    22 months ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    Unusual start time: Thursday, May 26, 2022 at 00:35UTC+7

    Aha

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22 months ago, # |
  Vote: I like it +12 Vote: I do not like it

Rubbish time for Chinese users.

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22 months ago, # |
  Vote: I like it -21 Vote: I do not like it

I think in this contest, the record would set up for the lowest number of participation.

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22 months ago, # |
  Vote: I like it -29 Vote: I do not like it

Timings are not unusual , but absurd.

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22 months ago, # |
  Vote: I like it +21 Vote: I do not like it

I think most of Americans can participate now, And also I am wondering that people in Los Angeles always participated in CF contests at 4 or 5 A.M

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22 months ago, # |
  Vote: I like it +62 Vote: I do not like it

As a tester I should say: Don't even think about skipping this round. Just look at how many testers lost their opportunity to participated in a rated contest(that takes place once in eternity). Show some respect

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    22 months ago, # ^ |
    Rev. 3   Vote: I like it +7 Vote: I do not like it

    Wish I could bro. But start time is same as my sleep time. I'd be sleepy entire contest.

    How about shifting by 1 day and have usual timing

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

    I don't want to skip it, but look at the time. I believe most East Asian competitors have to withdraw. Anyway, that would be a good time to American participants.

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22 months ago, # |
  Vote: I like it +13 Vote: I do not like it

how far is it (−∞) possible???

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

Indian night owls there you go...

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

Hoping for strong pretests this round. Suffering from weak pretest syndrome since last few rounds.

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22 months ago, # |
  Vote: I like it -8 Vote: I do not like it

what is -∞

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

    The rating which is not achieved by anyone till now..

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

Best of luck!

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22 months ago, # |
  Vote: I like it -10 Vote: I do not like it

Can you change the starting time, It is not suitable for most users! It would be better if the contest is held as usual, I mean at 19:35 (UTC+5) More specific time: (14:45 UTC+0)

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22 months ago, # |
  Vote: I like it +58 Vote: I do not like it

wow, i thought that i'm on codeforces, not on atcoder

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

I hope my pupil friends will contribute to stock up my lost ratings, in this round despite the unusual start time.

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

Time can be usual?All the eastern asian countries people is sleeping.

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22 months ago, # |
  Vote: I like it -10 Vote: I do not like it

what ! 2:35 AM?!??

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

Honestly, with 420 problems solved, a (timezone dependent) leftover max streak of 69 from last summer (a summer of failure tho), and a new peak rating (+175 delta: you know, for kids!), I was thinking of retiring from cp on a completely middling note.

That and I still don't know if I'll be able to clear out enough time in the middle of the afternoon on a weekday tomorrow...

Buuuut, it's mildly annoying that my 'actual' peak rating was on account of the april fools contest... so, screw it, I'm in (as long as daycare doesn't crap out randomly (again)).

Place your bets on how this choice will age, but you'd probably be right to think of rancid dairy more than fine wine :P

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22 months ago, # |
  Vote: I like it +48 Vote: I do not like it

omg ukrainian round

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22 months ago, # |
Rev. 2   Vote: I like it +18 Vote: I do not like it

Hope to see brilliant problems, hope new colors for all

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

What a pity that I'm unable to take part because of the too-late time. I have class to attend the next morning

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22 months ago, # |
  Vote: I like it -9 Vote: I do not like it

Can someone please tell what's wrong in this solution of mine , its problem D from last contest . I got a WA on test 192

Solution link

Thanks !!

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

    You r using map<pair<int,int>,int> in place of map<pair<long long int,int>,int> AC Code

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

It would be funny for CF to schedule contests with time table evenly distributed among 24 clocks, this way we may have a rough statistics about each timezone's skill distributions (or non-primary account distributions, even the cheater distribution)

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22 months ago, # |
  Vote: I like it -23 Vote: I do not like it

Anton orz

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    22 months ago, # ^ |
      Vote: I like it -13 Vote: I do not like it

    Thanks for taking some of your very precious time to delight us with this highly intelectual comment.

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22 months ago, # |
  Vote: I like it +27 Vote: I do not like it

sleepforces

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22 months ago, # |
  Vote: I like it -11 Vote: I do not like it

Contest should be shifted to next day.

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22 months ago, # |
  Vote: I like it +16 Vote: I do not like it

start the contest now, codechef servers are down lmao

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

When you want to codeforces contest on its regular time and then it is postponed for 3 hrs , then you move to give a codechef contest and that site is down. Its like u have water but u cant drink it

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

well hello to everyone from codechef

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22 months ago, # |
  Vote: I like it -6 Vote: I do not like it

Is anyone going to attend it after delay also?

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

LOL.. Now this round needs to be postponed by an hour as well!

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

GG CC postponed and cf unusual timing, Now I can watch rcb batting with peace

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    22 months ago, # ^ |
    Rev. 3   Vote: I like it +1 Vote: I do not like it

    what to see they are rubbish as always

    upd: my bad patidar on fire

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

    It was a perfect show boom boom patidar

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22 months ago, # |
Rev. 2   Vote: I like it -18 Vote: I do not like it

bad time for Indians now ig :(

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

I hope i'll get my rating back)

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

Hopefully, with unusual time comes unusual performance and I get mad positive rating points :)

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

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

The timing is perfect for me XD

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22 months ago, # |
  Vote: I like it -129 Vote: I do not like it

Hi antontrygubO_o! Could you ban all r*ssians from participating? Thanks.

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22 months ago, # |
  Vote: I like it -96 Vote: I do not like it

Will the day finally come when Codeforces stops giving problems about subarrays, substrings, subsequences and bracket sequences? Come on guys, the problems are so boring that it's even not worth competing in such contests.

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    22 months ago, # ^ |
      Vote: I like it +131 Vote: I do not like it

    No

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      22 months ago, # ^ |
        Vote: I like it -10 Vote: I do not like it

      sir, please stop giving problems about anything, including subarrays, substrings, subsequences, bracket sequences. Come on guy, the problems are so boring that it's even not worth competing in such contests

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22 months ago, # |
Rev. 2   Vote: I like it +9 Vote: I do not like it

Looks like a Div3 Round by seeing A, B, and C.

Anyways the problem was very good and I enjoyed it though I made a Wrong submission on C due to a silly mistake.

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

done with ABC, should I even try D?

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

Speedforces?

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

The best round for me. But I think I'll have TL in C((

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22 months ago, # |
  Vote: I like it +49 Vote: I do not like it

The worst round in recent times

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22 months ago, # |
Rev. 2   Vote: I like it +84 Vote: I do not like it

A, B, C -> DIV. 3 | D, E, F -> DIV. 1. There was no DIV. 2 today.

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

Free Advice: 30mins left in contest, even if you start solving now, if you could do D you'll be on top 200 :)

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22 months ago, # |
  Vote: I like it +29 Vote: I do not like it

Any way to report people like him?

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22 months ago, # |
  Vote: I like it +41 Vote: I do not like it

Thanks dario2994. Without you, the contest would be unbalanced... orz

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22 months ago, # |
  Vote: I like it +13 Vote: I do not like it

why so unbalanced?

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22 months ago, # |
  Vote: I like it +26 Vote: I do not like it

If you don't have enough problems on your hand make less rounds. But please make quality rounds. Anything you can assume and make a problem based on some constructions is the worst problem idea.

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22 months ago, # |
  Vote: I like it +24 Vote: I do not like it

How to solve Div1B cleanly without a ton of if statements?

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

    split to 4 types of sequences 1)ABAB..ABA 2)BAB...ABABAB 3)ABA...BABA 4)BABA...BABA so split to substring without duplicates of letter. 1 and 2 contribute len/2 to c or d. 3 contribute x to c and len/2-x-1 to d. 4 contribute x to d and len/2-x-1 to c.

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

      This is the bad solution I am referring to. It frankly feels like awful bunch of cases (with a touch of greedy) and nothing else.

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

      I did the same but got WA on 3 :( may be wrong implemented :(

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22 months ago, # |
Rev. 2   Vote: I like it +1 Vote: I do not like it

How to solve Div2 D? T_T

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    22 months ago, # ^ |
    Rev. 3   Vote: I like it +16 Vote: I do not like it

    Warning — this solution is bad, there is hopefully a better one.

    Two consecutive same characters can never be part of the same word, so split on this. This leaves 3 patterns:

    1. Single Character (A / B)
    2. Repeating Interchangable (ABAB...BABA / BABA...ABAB) which becomes any combination of AB and BA + 1 remaining character (the first / last one)
    3. Repeating Non-Interchangable (ABAB...ABAB / BABA...BABA) which requires us to delete an A and a B from somewhere to use the opposite type.

    Try to fill required number of AB and BA from Type 3 directly first. Then use Type 2 if required. If we have excess of one and a deficit of the other even after this, then convert Type 3 pairs. Greedily use larger strings first since we'll always lose 1 A and 1 B during this interconversion, so we can get $$$\frac{|p|}{2} - 1$$$ copies of the opposite word from a Type 3 string of length $$$|p|$$$

    If you have a deficit of As and Bs, get them from any extra AB / BA after this.

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      22 months ago, # ^ |
        Vote: I like it +12 Vote: I do not like it

      I arrived at the exact same solution, but rage quitted while implementing, thinking there might be a better way as it is a Div1 problem.

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      22 months ago, # ^ |
        Vote: I like it +25 Vote: I do not like it

      You can check the number of A and B at the beginning and ignore it later on. The problem basically reduces into checking if we can create enough AB and BA.

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      22 months ago, # ^ |
      Rev. 3   Vote: I like it 0 Vote: I do not like it

      Oh, i tried doing it the other way, from Type 2, then type 3 smh

      Actually, tried both ways, some impl bug...

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

what is the approach behind the D, Please mention if you know Thanks,

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

    If my solution passes the system test, then D's solution is just a heavy implementation of some case analysis.

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

    This is how I did , Look For continuous blocks of A and B if the size of continuous block is greater than >=3 then all the middle characters must count only in a (if block is of A's) or b (if block is of B's) for example using 0 based indexing if if from i to j all are A's then all A's from i+1 to j-1 should definitely contribute of a because they are not proceeded or succeeded by B if(i==0) the first A should also contribute to a if(j==(n-1)) the last A should also. Now We are left with multiple strings of type ABABAB... or BABABA... and these strings are separated from each other by when we detect consecutive A's or B's. Now we sort these string in ascending order of size and check if it is possible to get c AB's and d BA's from them. Also if the leftout strings are odd in size then it must contribute atleast one character to a if it starts with A else to b.

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

      i had same idea, but it still seemed kind of stupid solution to me lol

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

ABC (DIV2) speedforces D (DIV2), are you kidding me?

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22 months ago, # |
  Vote: I like it +35 Vote: I do not like it

This is still an unbalanced round. For div1 users, your ranking will depend on how fast you solve div1B. For div2 users, your ranking will depend on how fast you solve div2C. Problems are good, but either too hard or too easy.

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22 months ago, # |
Rev. 2   Vote: I like it +42 Vote: I do not like it

Oh yeah, another shitty speedforces round, more like ABBEFF, not ABCDEF (div 2)

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22 months ago, # |
  Vote: I like it +26 Vote: I do not like it

How do you solve Div 1C? Spent the last hour and a half and I still can't think of a good solution :(

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    22 months ago, # ^ |
      Vote: I like it +16 Vote: I do not like it
    Hint1
    Hint2
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      22 months ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      Wait, how does hint 2 lead to $$$answer \leq 2$$$.

      What if we also have large peaks and large troughs in the the region we fold? Isn't it possible to require upto $$$\log(n)$$$ folds in that case?

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

        Find the peak of the prefix vals, then 2 operations: 0, peak and peak, n is enough. When you choose 2 endpoints with different values to rotate upon, only the values outside the range will 'flip' sides. So when you choose 0 and the highest value, there will be no higher value to 'flip' to the negative side.

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

          What about ()))((((())))((())? Isn't solution to flip 2 16.

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

            Of course, you still need to handle cases where just picking 1 reverse suffice, but at least you know that you can always solve in at most 2 reverses.

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              22 months ago, # ^ |
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              I see, makes sense, thanks!

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

Avengers Interviewer: What's your superpower? Me: I can solve problem D.

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

15min solving and rest just staring at the screen :)

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22 months ago, # |
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Reminded me of Round 728. Similar gradient lol.

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22 months ago, # |
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Anyone pls tell that what was the approach to solve c:*

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

    1.Sort the array 2.Check if length of array is odd or even 3.If Odd then output NO as you will not be able to form a circular array if length is odd, you can check this on your own. 4.If its even, then put the elements like [A[0], A[N/2+0], A[1], A[N/2+1], A[2], A[N/2+2], ...]. 5.Now check if its circular by doing if else example if (a[j]>a[j+1] and a[j]>a[j-1]) or (a[j]<a[j+1] and a[j]<a[j-1]) continue else return False, for the 0 element check it with 1st element and last element and for the last element check it with (last-1)th element and 0th element. 6.At last if all the things go correctly then output the array along with a yes else no.

    Hope it helped!

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

      pls tell that why we can't create circular array in this manner that , res[ind++]=arr[i]; res[ind++]=arr[n-1-i] why we need to take element from the mid

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

        Try for this sample 1 2 3 4 4 4 7 8 9 10.

        Spoiler
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22 months ago, # |
Rev. 2   Vote: I like it +4 Vote: I do not like it

Is there a clean way of doing div 2D/div1B or is it just horrible implementation?

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

So sad, that cuz of debug stuff left, i lost +-800 places :( It could be an easy +175, but still +60, so i am fine with this :)

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

I'd really appreciate if anyone could enlighten me with an idea or hint for D?

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    22 months ago, # ^ |
    Rev. 2   Vote: I like it +7 Vote: I do not like it

    I don't have the solution, but i was able to make the following observations:

    Take a string: "ABAABBABAB" Since we don't have to create AA and BB, we can effectively split the above string as [ABA][AB][BABAB] now the task has been reduced to satisfy the number of a,b,c,d (a: count of A, b: count of B, c: count of AB, d: count of BA) using these sub-strings, which are strictly alternating.

    Again for strings of odd length:

    ABABA: we can take out single A and reduce count of a by 1.
    BABAB: we can take out single B and reduce count of b by 1.

    but taking out first character or last character causes problems: A+BABA or ABAB+A A decision has to be made to either remove first or last character. (I wasn't able to figure this out)

    For strings of even length:

    ABABABAB notice removing AB or BA doesn't really affect the identity of string, what i mean by that is: ABABAB remove either AB or BA last 2 remaining characters will always be AB for this string. For BABABABA remove either AB or BA last 2 remaining characters will always be BA. So you can use them to satisfy c and d.

    In the end you must have some AB and some BA with you and you can easily determine what to satisfy with them, AB or BA or A or B.

    Hope this makes sense.

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

guys I want to ask you, I have submit problem A late say, then get AC, after time i resubmit again does it mean i will lose points or no, or it depend if it the second submit AC or WA, please tell me about it, and sorry for the stupid question, and if the announcement don't say it will be hack duration, then if i get AC no one will hack me or I will get WA after contest by adding pretests, thanks again.

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    22 months ago, # ^ |
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    if you resubmit problem, you lose all points and get as much as it costs now

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

Everyone is competitive Coder, Until D arrives Just joking don't take it serious

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22 months ago, # |
  Vote: I like it +72 Vote: I do not like it

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22 months ago, # |
  Vote: I like it +9 Vote: I do not like it

Why was the difficulty in div 2 like AABEEF

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22 months ago, # |
  Vote: I like it +29 Vote: I do not like it

GreedyForces

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22 months ago, # |
  Vote: I like it +12 Vote: I do not like it

This is my first codeforces contest where I solve exactly $$$0$$$ problems and guessed how to solve $$$3$$$ (with pretests passed).

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

i noticed that you can divide the string into blocks creating a new block once you reach two consecutive equal letters and the problem can be reduced to finding a way to get at least c ABs and at least d BAs only. Can this be done with dp or greedy?

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22 months ago, # |
  Vote: I like it +22 Vote: I do not like it

Who knew giving the contest this late would result in a bad outcome.

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22 months ago, # |
  Vote: I like it +44 Vote: I do not like it

Why so few construction problems? xD

In div1D, we can make a smaller answer than "choose one element from each cycle in $$$P$$$, take their max-min multiplied by 2"? I have a solution that gives exactly this minimum but it gets WA.

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    22 months ago, # ^ |
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    It is possible to archive answer: 2(#CYCLES-1). Consider p={1,3,2,4} -> cycles {1}, {2,3} {4}. One of the optimal solutions with score 4 is: {1,3,4,2}.

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    22 months ago, # ^ |
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    Came up with the exact same minimum, got tricked by the samples.

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22 months ago, # |
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Good contest, enjoyed it!

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22 months ago, # |
  Vote: I like it +18 Vote: I do not like it

This contest was super unbalanced, A-B-C was like easy problems(for my level). Solving D was Like solving E

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

How to correctly split the last sample from (div2) 1686D - Linguistics?

1 3 3 10
BBABABABABBBABABABABABABAABABA

I thought you have to at least split into B, BABABABAB, B, BABABABABABABA, ABABA and then I can see how to fulfill 1 3 2 11, but I haven't found a valid split for 1 3 3 10, yet.

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

    B = 1 B

    BABABABAB = 3 ABs, 1 BA, 1 B

    B = 1 B

    BABABABABABABABA = 7 BAs

    ABABA = 2 BAs, 1 A

    Total: 1 3 3 10

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

      Of course! Thanks. Found the bug in my ugly solution 158469628...

      Spoiler: The Bug
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22 months ago, # |
  Vote: I like it 0 Vote: I do not like it

thanks for great contest !!!

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

    Wow, you've done incredible job! Congrats on winning this contest!

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22 months ago, # |
  Vote: I like it +118 Vote: I do not like it

ACD1 are nice problems, but overall I dislike the round because all of the problems are purely ad-hoc :(. Would be really nice to have some data structure, DP or algorithmic problems.

It might be that D2 or E fits those categories, but it doesn't really help when those two problems get 5 solves total.

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

Div 2E / 1C Problem Title is very relevant to summarized participants' feedback

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22 months ago, # |
  Vote: I like it +21 Vote: I do not like it

Y div2D so ugly.

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    22 months ago, # ^ |
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    weren't there just 4 cases?

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      22 months ago, # ^ |
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      3 cases, the odd-length alternating islets are interchangeable regardless of their starting letter.

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22 months ago, # |
  Vote: I like it +43 Vote: I do not like it

'D'epressing Contest

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

Why hacks aren't added yet? so many wrong got ac.

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22 months ago, # |
Rev. 2   Vote: I like it -10 Vote: I do not like it

looking for problems [D: F] div2 I think we are talking about the tourist S contest version

however, great contest with great ideas am waiting for the Editorial for Upsolving

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22 months ago, # |
Rev. 4   Vote: I like it +14 Vote: I do not like it

people start downvoting the contest, What was the reason ACC to you?

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

I hacked someone on C

when will my testcase added in question C , waiting...

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22 months ago, # |
  Vote: I like it +32 Vote: I do not like it

The problems I solved are really boring but the problems I didn't solve seem pretty good so overall 6/10 good round oomfie

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

I miss good div2D pblms.

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

I was waiting for this for a long time, since it probably is my last round before summer. Turns out I was waiting for a speedforces with a huge rating loss for me because I'm not good at solving problems fast. Wow, I feel so betrayed(( i mean that's my fault but I'm sure there is something wrong.

also, why didn't Anton invite other people apart from masters or gms to test the round? Why only 1 specialist from div2? I think that was his mistake, nobody could give appropriate feedback to div2 set, and it ended up being this.

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

Ratings updated preliminarily. We will remove cheaters and update the ratings again soon!

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    22 months ago, # ^ |
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    What about adding Hack test cases? There are so many wrong submissions who got ac on C.

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22 months ago, # |
  Vote: I like it +24 Vote: I do not like it

Might have benefited from having more than one div 2 tester, just my thoughts.

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22 months ago, # |
  Vote: I like it -154 Vote: I do not like it

This round is complete shit but heavily upvoted. The round 792 had usual problems — and it was heavily downvoted only because the author was not as famous as the author of today's round.

Guys, stop praying for your idol Anton — he might be a good contest coordinator and a good contestant himself but he is not a good problem writer. If you also didn't enjoy this round as much as I did not — hit the downvote button.

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    22 months ago, # ^ |
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    Is the round complete shit if you don't like it?

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    22 months ago, # ^ |
      Vote: I like it +17 Vote: I do not like it

    For me at least, having adhoc problems that require algorithmic thinking is better than having 5 Li-Chao Tree problems with heavy constant optimization with very tight TL, but I have to admit that the difficulty curve for this round could have definitely been better, but I still think the problems were good.

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

I tried to solve Problem D with DFS, and it worked well.. until I got Time Limit Exceeded on a pre-test.

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    22 months ago, # ^ |
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    and what's wrong with it?

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    22 months ago, # ^ |
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    I feel like counting A B AB BA and ABA is enough.

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      22 months ago, # ^ |
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      Break string into substrings till 2 consecutive has not come... For example ABABABABBABAA Break down:- ABABABAB BABA A

      Now you can see...

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

I'm getting; wrong answer Jury found the answer but participant didn't (test case 1435) 158465505 not getting why is it so?? can anyone help

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    22 months ago, # ^ |
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    if(t == (number of testcases)) print test case 1435.

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      22 months ago, # ^ |
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      Giving same error,, not working

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        22 months ago, # ^ |
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        it is the way how you can see what's wrong.

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

5400 ACs for div2 C. Totally seem legit to me.

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

Hi can someone tell me that why does this solution fail the test cases in div2 C while this works fine, I mean we are doing the same thing in both of the solutions just by changing the order of fill up why is this causing an error. I can't understand what's going wrong with the first solution that the second one is taking care of.

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

    In line 35, you first filled in by 1, 3, 5, .... Then in line 38, you filled in by 0, 2, 4, ....

    This means the first element filled is NOT in the leftmost slot. The first element (which is the largest one) is begin sandwiched between 2 elements.

    The test case of 1 2 3 3 4 5 will cause your code to fail. You will try to fill in the array as: x 5 x 4 x 3 first, then 3 5 2 4 1 3. The first 3 and the last 3 will cause the array to fail.

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

Why do we need to check the array after creating in $$$\text{DIV 2 C}$$$, isn't it enough to check whether any element came more than $$$n/2$$$ times ?? (if $$$n == even$$$)

Can anyone please help why this code gave WA??

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

    1 1 2 3 should return YES. 1 2 2 3 should return NO.

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22 months ago, # |
Rev. 2   Vote: I like it +26 Vote: I do not like it

Thanks for wasting 135 minutes of my day. What's the point of only having one Div. 2 tester? Do coordinators truly believe they are some all-knowing beings whose judgement can't be flawed and thus they don't want to deal with feedback for problems they wrote?

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    22 months ago, # ^ |
      Vote: I like it -16 Vote: I do not like it

    What happened?

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      22 months ago, # ^ |
        Vote: I like it +24 Vote: I do not like it

      The Div. 2 round was incredibly unbalanced. ABC had almost the same amount of solves, while D had much, much fewer. I remember at the 50 minutes to 1 hour mark, the solvecounts for ABC were all above 5000, while D had 20 solves. Such issues can be avoided if there are a variety of testers.

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22 months ago, # |
Rev. 2   Vote: I like it -26 Vote: I do not like it

Please can anyone tell why my overall ratings is deducted by 13 ...though I was able to submit 2 accepted and one wrong code...my rank was around >7k.

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

    Because you performed worse than you were expected for your rating. It's not like you get rating from solving anything

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

When will the editorial be out?

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22 months ago, # |
  Vote: I like it +22 Vote: I do not like it

This contest was really fun!..what do you guys think

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

Hi, sorry if this is not the place to comment about something I'm going to write.

I think I've been falsely flagged by the system for rules violation, you can read its (system) message here:

Message from system

Basically, it says that my solution for problem C 158431590 significantly coincides with superMAXX's solution 158426434 and dhruvrathi04's solution 158452721.

I guess the system flagged because of this part in the code

My solution
superMAXX's solution
dhruvrathi04's solution

But isn't it a pretty common implementation for checking whether each element in the constructed array is a local minimum/maximum? what do you guys think?

MikeMirzayanov and any other Headquarters, can you take a look on this?

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

    MikeMirzayanov and other Headquarters.

    Regarding: I got a message from the system that my solution for 1686C - Circular Local MiniMax 158452721 significantly coincides with solutions superMAXX/158426434, Andyoshino/158431590, dhruvrathi04/158452721

    I want to inform you that this can only be a coincidence and that you should look into the system again and rectify this error.

    I had made 5 submissions for this problem during the contest and all of them had this part of the code which looked similar.

    My first submission 158433352 Second Submission: 158436773 Third Submission: 158442044 Fourth Submission: 158448587 Fifth Submission: 158452721

    All the codes are written by myself and I have not done any violation. I used my local system for writing the programs during the contest and did not use any online IDE.

    I request you to please look into the matter once again and do the needful.

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

It was really a nice round .

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

why the graph is not showing rating of this contest now?

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

    Removing cheaters and recalculating the rating change accordingly. It happens after every round

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      22 months ago, # ^ |
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      but this time there was no warning message about it...

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      22 months ago, # ^ |
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      but my ranked increased by 100 it should be reduced when cheaters are removing

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

is this round unrated?

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

Nice contest! Thanks!

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

why contest has become unrated?