Elimination Round — Bayan programming Contest 2014-2015
By BYN, 10 years ago, In English

Elimination Round will start today, 14:30 (UTC) and only contestants who have passed Qualification Round will be eligible to participate.

Score for each solved problem is calculated based on these values:

  • n = No. of accepted submissions
  • t = Contestant's submission time
  • p = Number of contestant's wrong attempts

To receive the latest news fast, follow us on twitter: @bayan

Update 1: The Elimination round is over, and let's face it: It was far from good!

Yes, we're aware of all the issues, and we know that nothing is more nerve-racking than facing those issues during a competitive contest. So, first thing first, we'd like to sincerely apologize for all the inconveniences caused.

In last hours, we thought that the contest has become too hard, so we made a major wrong decision: omitting a hard problem and adding a simple problem as our first question without enough time. Hint: never make any changes to the problem set in a hurry.

Update 2: Editorial is on the way. Source codes will also be avalible in a few hours.

Update 3: Unfortunately we have found some cheaters. As mentioned before they will be banned for ever from Bayan Programming Contests.

Update 4: The editorial is now available.

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

Comments Comments (155)
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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Who are the winners of T-shirt of Qualification round?

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

When will I see the countdown?

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

    Elimination round is going to be held on contest.bayan.ir, so you are not going to see the countdown here. Elimination will start in less than 1.30 hour.

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      10 years ago, # ^ |
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      But when will I see the countdown on contest.bayan.ir?

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        10 years ago, # ^ |
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        There is one already!

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

          I see only Available soon

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            10 years ago, # ^ |
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            I saw only Available soon

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

shouldn't it be something like t/T instead of t/500?

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

    No.

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      10 years ago, # ^ |
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      but 't' is not number — it is amount of time. Did you mean that t is I don't know.. number of minutes from start to submission?

      and will we know about WA/AC immediately or after contest?

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

        yes, t = time of submission in minutes. and yes, you will see your submission verdict immediately.

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

Hi, I'm not sure this is a good place to ask, but I've started receiving email contest announcements in Russian. Can I switch that back to English somehow?

Also: Is there a help forum somehow that I can't find or is this the only way to address you?

Best, Esuhi

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

    We are not sending Russian emails. Probably Codeforces is sending them for Russian contestants.

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

how can i submit problem

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

150logn ?
I know that O(logan) = O(logbn) regardless of a, b values (assuming they are greater than 1), but logan ≠ logbn :). Is this log2? Or natural logarithm? Please clarify.

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

To make it clear — we have full feedback, yes? I mean, immediately after submitting file, I will be informed whether is this correct output? If so, am I right that final results will be immediately available after the contest? No systests, no freezing, right?

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

    Yes. Scoreboard will be valid all the times.

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

      What a great information :)! First contest where I won't fall 500 places because of some stupid bug in a hard problem : p.

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10 years ago, # |
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in this formula n is no. of accepted submissions of this task til my submission or in whole contest?

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10 years ago, # |
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It was written solving 1 will qualify you to the elimination round .. I solved two .. Yet showing not qualified ?

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

the bottom left corner always shows:
Disconnected. will retry in X seconds

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

Doesn't it overlap with CookOff?

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

I really like the Ui of the Bayan website :)

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

Sorry to say this, but it is too slow, just like the Shortcut Round. I cannot log into the contest area no matter how hard I try.

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

I can't see any problem :(

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

Connecting =(

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

Contest has started, I could connect ("Receiving live updates"), yet the Problems tab remained empty. Are we solving 0 problems instead of 6?

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

Nothing works, can't see any problems.

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

The contest time countdown started, we're 2 minutes into the contest, but there are still no problems in the place where was the placeholder.

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10 years ago, # |
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Is it working for anyone? In theory the contest started already but i can´t see any problems... it only tells me "Disconnected, will retry in x seconds"...

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

Problems are visible now

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10 years ago, # |
  Vote: I like it +17 Vote: I do not like it

I just tried to solve a problem but it says Firefox can't find the input file.

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

I see problem but I cannot download input file!!!

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10 years ago, # |
  Vote: I like it +65 Vote: I do not like it

Instead of providing me with an input, it says "Webpage not available".

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

Can't download test input, and my time is running out. Come on guys, why are there bugs again. It's a time-penalty competition so such bugs are crucial to results :(

EDIT: Will penalty from first submission be removed?

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10 years ago, # |
← Rev. 2   Vote: I like it +28 Vote: I do not like it

Hardest problem: how to get test input

Edit: Even after announcement all I get is a blank "Untitled" page... :/

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

This contest arena is begging me to switch to CodeChef Cook-off in 50 minutes.

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10 years ago, # |
  Vote: I like it +68 Vote: I do not like it

It's the most awful contest which I've been participated ever(

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

My ticket has expired because site was down.

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

Problem B. Is the time in minutes or hours or something else?

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    10 years ago, # ^ |
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    I think it's in second

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      10 years ago, # ^ |
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      Sent a clarification more than 10 minutes ago, still no answer. Where have you read that the time is in seconds?

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        10 years ago, # ^ |
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        because in the last testcase, the time is 28801, 8 hours = 28800 seconds

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

My solution has been pending for 10 minutes, is it only me?

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10 years ago, # |
  Vote: I like it +45 Vote: I do not like it

I don't know why problem A is so hard to get accepted, although it is a very easy one.

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

    same here, I have no idea why I keep getting wrong answer

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

    Seems easy but, I think some description is missing, so lots of WA :(....... I'm gonna participate Codechef-Cook-Off !! Bye bye BAYAN !!

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10 years ago, # |
← Rev. 2   Vote: I like it +12 Vote: I do not like it

How must lines end in my output file?

\n

\r

\n\r

Или я просто не умею решать камень ножницы бумага? =))))))

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

    Я пробовал "\n" и "\r\n", с и без перевода строки в конце, не помогло.

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

      Мне тоже не помогло. Может проблемы с кодировкой? =)

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

CookOff, there you go :D

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

A — hardest problem ever. Only 256 right answers out of 2,5k submissions at the moment. DAFUQ IS GOING ON!? That is so embarassing!!!

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

    It is getting harder and harder, now with 50 accepts.

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

    You too(, Brutus?) :D

    In fact, due to this, I harbour a deep suspicion that the system is rejecting some type of correct solutions. But that can't be checked until after the contest.

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10 years ago, # |
  Vote: I like it +79 Vote: I do not like it

If someone ever ask me about the definition of failure I will tell him "Bayan contest".

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

    I've submitted the same code 10 times....and the last time it has got Accept!
    =))

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

What's going on?

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

"Question A will be rejudge". :D

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

Problem A was rejudged in the middle of the contest, and it went down from 500+ solves to just 36. (That's a 1% success rate for submissions.) There's a crash every 3 seconds, and test data doesn't load half the time. This is probably the worst contest ever organized...

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

    I'd say, that was second worst contest ever... because of their "shortcut!" round.

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

Should I input/output to file or standard input/output ? In the qualification round I used stdin/out and still got AC. Now they say I need to use file input/output. But what file ?? For input it's probably like "A.txt" but whatabout output ? Also, sometimes it's really hard to submit/download input. And while I was writing this comment, my problem A got AC with the exact same code of 8 previous attempts :| Maybe we should hold another elimination round, on codeforces platform instead ?

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

Is there a scoreboard for spectators?

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

Thanks for the contest [already], but I'm not going to participate next time. Even after this comment it seems that platform doesn't work well, so what is the point?

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10 years ago, # |
  Vote: I like it +113 Vote: I do not like it

Making your company famous: you're doing it wrong.

If it takes place on your platform next time, I'm definitely not participating.

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

"Question A will be rejudge."why?

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

Does Problem C has a tricky solution or there is a classic way to do it?

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

    Are you seriously asking about solution during the contest -_-...?

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

      I am seriously asking during the contest, while waiting for the answer after the contest :)

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

I'm not gonna partecipate again! I spent two hours on the first because of wrong answers, but after all they were all accepted!

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

    I've spent two hours with first problem too :( I'm not implying I would have solved more tasks but it's disappointing.

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

      Well I think I were near to a solution for C, but I had no more time left:(

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

    And I gave up the contest after repeated wrong on A and went to participate in codechef cook off. Now I am knowing that I had passed A

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

    me too :|

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

how I solve problem C?!

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

    Finished.

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

    Let's try to construct the path backwards. The inverse path begins on the biggest number of the input.

    Suppose you have already stepped on some tiles, and you need to step on a next tile. Note that as we're going backwards, the final number on a tile is defined by the first time we step on it. For this reason, when going to the next tile, you can only use the tiles that you have already stepped on previously.

    So do a BFS from the tile you're on to the next tile you need to step (using only tiles already stepped) and check if you can reach the next tile in the number of steps required. If the bfs returns a smaller distance than required, you can add any multiple of 2 to the number of steps in the path by simply going back and forth between two squares.

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

      thanks a lot.

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

      you can add any multiple of 2 to the number of steps in the path by simply going back and forth between two squares.

      Provided two suitable squares exist.

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

        If you are checking in order of increasing values using BFS, two suitable squares will always exist unless it is the last one(which is the same condition as two highest values on the grid must differ by 1).

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

      Explicit BFS is not really needed. You just need to prove that a backward path exists, you don't need to find it. The solution to the problem is "YES" if and only if the following 4 conditions hold: - (1) All numbers are different - (2) Every pair of neighbors have different parity. - (3) Every tile, except the MAX, has a larger neighbor. - (4) The MAX tile has a MAX-1 neighbor.

      Condition (3) ensures you have a backward path from any tile other than the maximum, and condition (2) ensures this path is of the right parity.

      UPDATE: Forget this... it's wrong... BFS is needed, because otherwise the path may be too long. Example: 1x4 grid with values 2 3 4 1.

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

        Consider following grid

        1 200 101

        300 301 2

        All your conditions are true, but answer is NO

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

one positive fact:

problems were interesting.

Hope for a better platform.

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

Considering the amount of problems with the platform(slow, those rejudges etc..), the number of participants receiving t-shirts should be increased by 10-20 :D

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

    Your comment will get 20 likes, and I'm one of them giving! ;)

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10 years ago, # |
← Rev. 2   Vote: I like it +41 Vote: I do not like it

Why don't you hold off the contest on Codeforces?!
When such a great system like Codeforces is available what's the reason to don't use it and instead, use a weak, slow and totally bad system like yours?
I really hated the delay, the file input output, your slow system and many times not loading, you had file input output but still you had problems with your judging for problem A, you didn't answer too clarifications and ...

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

Can people who won a T-shirt before (in ShortCut, Qualification, WarmUp Round) win T-shirt again in this contest?

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10 years ago, # |
  Vote: I like it +36 Vote: I do not like it

http://codeforces.me/blog/entry/13542#comment-184595 — here I said that according to weird (ans stupid) rule "one country — one finalist" I think I got higher chances to qualify than without it, but it turned out, that I was in TOP20, but Eryx was better, so it is exactly the opposite -_-. This is my first time I ended in TOP(number of finalist) in qualifications to some onsite competition, but I didn't qualify, because of that ridiculous rule :(!

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

In problem C — GridHistory — Can anyone show me a path that is compatible with the first sample? (2x2 grid, first row 4,11; second row 7,12), because even after computing an exhaustive search I haven't been able to find any... I don't know what I've done wrong...

UPDATE: I misundertood the problem completely :( I interpreted it as "When he enters a cell, he erases the number written in that cell and writes the last number he has written ON THAT CELL plus one", rather than "the last number he has written ANYWHERE IN THE GRID :_(

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    10 years ago, # ^ |
      Vote: I like it +13 Vote: I do not like it 
    a b 
c d

c->a->c->a->b->d->c->d->b->d->b->d
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    10 years ago, # ^ |
    ← Rev. 4   Vote: I like it +5 Vote: I do not like it

    In steps:

    0 1
0 0

4 1
3 2

4 5
7 6

4 9
7 8

4 9
7 10

4 11
7 10

4 11
7 12
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    10 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    You can go over a grid space more than once. So starting from the top right square the sequence of operations is: DLUDUDRUDUD. (Where D = down, L = left, etc.)

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

    on 1-based index : starting at time t=4: t=4: 1,1 t=5: 1,2 t=6: 2,2 t=7: 2,1 t=8: 2,2 t=9: 1,2 t=10: 2,2 t=11: 1,2 t=12: 2,2 basically each cell can be visited any number of times(the last visited time is its final value :P )

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

    I misunderstood the question. I thought it said he rewrites the number with the original number on that cell plus one....

    Looks like you made the same mistake.

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

    I made the exact same mistake and lost top 20 because of it. This is why contests usually have explanations of the sample input.

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

Ranked 4, but I can't go to final. What a sad story. Congrats to hos.lyric and sillycross. And I think Hiroto Sekido is much more unlucky than me. T_T

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

    I think because hos.lyric had made it to finals using Shortcut round, laycurse has also qualified for the finals.

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

Question to organisers. In case someone from TOP-20 country-wise doesn't accept onsite invitation, do you offer this place to somebody else or no? The reason I'm asking is because my country seems to be TOP-21 if I calculated it correctly.

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

The platform is less terrible than for the shortcut round, still terrible.

The problems are interesting, except the straightforward implementation tasks A, B and E.

Apologies for having the wrong flag next to my name on the scoreboard, I only now realized that the nationality is relevant, not the residence.

About the onsite finals, https://www.gov.uk/foreign-travel-advice/iran/safety-and-security does not sound very reassuring. What is your opinion?

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

    What is your nationality? Again, the reason I'm asking is that because it may move my country from TOP-21 into TOP-20 :)

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    10 years ago, # ^ |
      Vote: I like it +46 Vote: I do not like it

    Let's take a look what this site says about your own country: https://www.gov.uk/foreign-travel-advice/serbia/safety-and-security ;)

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

      Sounds accurate, and slightly less worrying than Iran. It's not my intention to offend anyone.

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

        This phrase "Kosovo’s independence remains an emotive issue for many Serbs." doesn't sound accurate to me because Kosovo is not independent country. Moreover, it's an interesting question — organizers didn't specify what nationality means in profile settings and didn't specify what country means — for example, Hong Kong and Chinese Taipei are Chinese provinces in my opinion so do people from those regions need additional spot in the final?

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

          Not to start any fights or offend anyone, but in my opinion Taiwan and China are different (I think most people who were on this year's IOI would agree) so they should get different spots in my opinion. However the question what exactly does nationality mean is still valid.

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

            For the purpose of this contest, a nation is what appears on the dropdown list on Bayan's website. If it's not on the list, it's a province.

            For the purposes of everything else, this is a complicated question and this is not the place to discuss it.

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

How to solve D? Did anyone prove it this time? :)

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

    The visible surface is at least the sum of the highest towers in each column, plus the highest towers in each row, plus the top surfaces.

    For each k, you want to minimize the number of columns and rows that contain a tower taller than k. Put the k highest towers in the smallest (by perimeter) rectangle that can contain them. This rectangle is either a square, or has sides that differ by 1, or has one side length equal to min(n,m). So, this is the lower bound for the area, and since we can actually do that for all k at the same time, it's also the upper bound.

    To calculate the number of ways, let's say you have the number of ways to pack the tallest a*b towers in an a*b rectangle, with a<=b, and want to calculate the number of ways to pack the (a+1)*b tallest in an (a+1)*b rectangle. You can extend the rectangle in either 2 or 4 directions (4 when a=b<min(n,m), 2 otherwise), and arrange b towers along the side in 2^(b-1) ways.

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

      About the number of ways, how to handle the part where the a*b rectangle lies on one of the edge (therefore only 3 directions to extent)?

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

        Don't even consider the n*m grid. Imagine just extending the rectangle (which is floating in space) until it has size n*m, and then placing it on the grid in the end.

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

          Aw I just found out that. Looks like I lack creativity :c...

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

how to solve E?

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

    Do the steps n-1 times: find out the edges that connect a new tower(toweres not yet filled with water). Choose the lowest cost, let the cost be x, then we make all other towers that is filling with water height at least x. The time needed is the total volume of water at that moment.

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

Who are the winners of T-shirt?

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

Will another additional Elimination Round?

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10 years ago, # |
  Vote: I like it -23 Vote: I do not like it

nerve-racking -> nerve-wracking

first thing first -> first things first

apology -> apologize...

BTW so happy that I didn't participate.

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

    But somehow you still care writing here...

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

    I think either racking or wracking works.

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

Will there be any editorial? I'm really curious about F.

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

Was this contest organized by same people as 2 years ago? I have a feeling that this is coming from completely new group of people which have too much ambition without anything to back it up.

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10 years ago, # |
← Rev. 2   Vote: I like it +16 Vote: I do not like it
  • Submitted B.
  • Solution pending for > 20 minutes.
  • Asked clarification.
  • Judge told me to just resubmit.
  • Resubmitted.
  • Both solutions were immediately judged as WA.
  • Slept immediately.
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    10 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it
    • Submitted E
    • Wait for pending
    • WA(expired)
    • Resubmitted
    • AC

    T_T

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

when you send T-shirts to winners?

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

    Did they announce t-shirt winners ??!!

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

I think I didn't make a mistake, that I didn't participate in this contest again :) ( http://codeforces.me/blog/entry/14185#comment-191632 ).

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

When are you exactly going to announce the T-Shirt winners? cause today is about to finish and according to twitter you'll be announcing it today.

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

    It seems that not only the platform is slow...

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

    Some duplicated accounts and a few more cheaters detected. Final rankings and tshirt winners will be announced soon.

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