jinlifu1999's blog

Codeforces Round #536 (Div. 2)
By jinlifu1999, history, 6 years ago, In English

Hello, Codeforces!

It's my honor to invite you to Codeforces Round #536 (Div. 2), which takes place at 12:35 UTC, January 31st, 2019. The round will be rated for all division 2 participants (with rating less than 2100). Also we warmly welcome those division 1 participants to join us out of competition.

This is my second round on Codeforces platform, and my first round was on January 31st, 2018, which is such a coincidence that I would like to say thanks to KAN for his awesome coordination and great dedication to this round. Besides, much thanks to testers Aleks5d, cyand1317, mohammedehab2002, ---------- for their excellent testing work. Also, I would like to appreciate the Codeforces platform created and maintained by MikeMirzayanov, without which the round wouldn't be possible.

In order to celebrate the Lunar New Year (or Spring Festival) originated in China on February 5th, I proposed the round with 6 problems, whose theme is about the Lunar New Year. In this round, you are going to help Alice and Bob to solve some problems in the preparation of celebrating the Lunar New Year in 2 hours. I hope that those problems can interest you and improve your programming abilities, at the same time, bring you luckiness as well as high rating in the coming Lunar New Year!

As a convention, the scoring distribution will be announced soon.

Again, wish you more luckiness and higher rating!

UPD1: Editorial is published.

UPD2: The scoring distribution will be 500-1000-1250-1500-2250-3000. Note that there are 6 problems and you will be given 2 hours to solve them.

UPD3: System test is finished. We are sorry for that technical issue which ruined your happiness. Despite the issue, I hope you do learn something from the problem set, which might be far more important than the rating itself. Enjoy problems, and looking forward to the next contest with better problem set to learn something new, which in my opinion is what Codeforces platform wants to provide us with. Thanks for your participation and dedication even after the unrated announcement. :)

UPD4: The real Editorial is published. Thanks for your patience.

UPD5: Despite that the round is unrated, I have to announce the winners, who deserve it because of their hard work.

Div. 2

  1. developer227

  2. newbieyzr

  3. Zharaskhan

  4. I_AM_CHTHOLLY

  5. mzhmxzh

  6. radoslav192

  7. Vit.C

  8. visitWorld

  9. yycdage

  10. xuzhiyuan1

  11. zhangqingqi

  12. Crossguard

  13. gtrhetr

  14. Itst

  15. HwSh

  • Vote: I like it
  • +438
  • Vote: I do not like it

Comments Comments (279)
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6 years ago, # |
  Vote: I like it +45 Vote: I do not like it

Nobody wanna write some comments and get upvotes?

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

Does it mean,that I can still up specialist,until new year?)

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

Isn't it a bit early to celebrate Lunar New Year on Jan 31th?

I hope there is a round on Feb 5...

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

    Isn't it family time?

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

      I actually had to skip having dinner out with family... only to find out this round will not be rated :( feelsbadman

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

    I thought you might be busy when the Spring Festival is approaching, so I made it earlier.

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

      大年三十肝CF不更美妙吗？ /滑稽

      It could be more pleasant to have a CFround on Lunar New Year's Eve .....

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

You wrote "Codeforce" instead of "Codeforces" in the title. I'm pretty sure you didn't do that on purpose since you wrote "Codeforces" everywhere else in the announcement. :-)

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

Thank god. I finally dun have to wait till 22:35 to join a contest and die to wake up the day after.

Love Chinese round :)))

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

When codeforces round starts early:

if (school && codeforcesround) { gotoschool=false; participateincodeforcesround=true; }

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

    probably you must be programming with java

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

is it unrated? if its unrated i wont partisipate

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

god its contest made by chinese please no +150 lines of code implementation problems

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    6 years ago, # ^ |
    ← Rev. 4   Vote: I like it +12 Vote: I do not like it

    Check out the implementation problem in SDOI2010

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

    To be honest, 150 lines are not much. Even a segment tree requires 40 lines, let alone something like a HLD and other complex algorithms

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

      And Red-black Trees are also loads of work.

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

      No. 150 lines is definitely not friendly (at least for me).

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

Really thank you for this Chinese Round!I've never seen such a Chinese-friendly round before!

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

Very good for Chinese programmers. I don't need to buy a box of coffee this time:)

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

Hope that those who are praising the Chinese round will also keep praising after the contest! :P

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

Again, wish you more luckiness and higher rating!

luckiness??? Most of the time I am so unlucky.

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

Nice to have a good timing for South and South East Asian programmers! Thanks for organizing the contest.

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

I hope the author was trained in the school of GreenGrape

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

Your former contest problem set is really awesome. I think this time also we get some awesome problems.

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

Incoming game theory problem ;)

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6 years ago, # |
  Vote: I like it -28 Vote: I do not like it

i hope the chinese are nice and don't mix math and programming like other people do. i couldn't partisipate in the last contest because of this and it was a smart move. if this doesn't have math i will be guaranteed a one-way ticket out of expert to candidate master.
i hope you won't crush our dreams with useless math, jinlifu1999 !

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

    Just interested, what do you call math? Is for loop like for (int i = 0; i<5; i++) also too complicated for you as it contains a plus sign which is obviously math?

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

      I think that even when the problem asked to print "Hello World", it's still a math problem with him.

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

codeforces admins are imposing censorship among the members of the community

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

why no one has taken the Bob handle yet?)

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6 years ago, # |
← Rev. 2   Vote: I like it -17 Vote: I do not like it

Will there be a translation into Russian? Sorry for bad English.

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    6 years ago, # ^ |
    ← Rev. 2   Vote: I like it -24 Vote: I do not like it

    learn English, it is the universal language and it will stay the universal language for a really long time. if you can't understand English you shouldn't be here. how do you code if you don't understand English? how do people like you exist?

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

      humble

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        6 years ago, # ^ |
          Vote: I like it -32 Vote: I do not like it

        you have anime profile picture and are from india and you expect me to take you seriously?

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

          It's not like the entire Codeforces community take you seriously either, you know.

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6 years ago, # |
  Vote: I like it +62 Vote: I do not like it

memefeb

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

Lunar New Year ,Alice and Bob ! The names and question story looking pretty much interesting ! Hoping for a great round ahed <3

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

oops seems like i cannot partisipate i have stuff to do whata bummer cout<<"poponar"

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

    wise decision because as it seems it will most probably have math and you don't want to trash your rating...understandable

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

Awesome Editorial jinlifu1999

Hope this Helps :P

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

What happened to The Editorial??

UPD1: The editorial is published.

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

Alice and Bob means game theory A or B

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6 years ago, # |
← Rev. 2   Vote: I like it +27 Vote: I do not like it

"Editorial" is up guys! haha

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

je veux devenir pourpre

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

Alice and Bob...

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

zici

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

Seems that hacking is important in this round... It's a challenge to us without doubt. Also...more funny will come.(maybe) I think it might be a special round.

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

So fast editorial!! XDDD

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

What a nice and brief editorial!!!

Just awesome.

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

Wow... what a nice contest time for koreans! (9:35pm over here :D)

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

I think it should be unrated.

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

rip contest :(

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

Contest should be unrated

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

I hope they fix it soon and the contest doesnt go unrated.

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

An OI contest....

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

all the submissions that I'm doing are in queue for the past half hour... is it happening with just me?

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

Semi-rated?

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6 years ago, # |
← Rev. 2   Vote: I like it +78 Vote: I do not like it

Seems strange. The author remembered to thanks MikeMirzayanov and bad thing still happens.

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

thx for very interesting and hard problems, none of those can't be solved in a minute, also I'm very glad to see a 228 hours queue so everybody can show his true skill.

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

Make it unrated, unfair to people waiting in queues for like half an hour and then getting a wa on a pretest.

Sad :(

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

Will it be rated?

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

Hope this turns out to be unrated. Submissions not getting judged since last 30 min. How to know "in queue" is "AC" / "WA" !!!

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

The contest was turning pretty good. But then long queue happened.

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

An extremely bad experience because the “in queue”！！

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

World's shortest horror story: "The round will be unrated because of technical issues".

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

Finally. Long live the contest!

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

Reminder: in case of any technical issues, you can use lightweight websites m1.codeforces.com, m2.codeforces.com or m3.codeforces.com

How to use m1.codeforces.com to resolve In Queue issue??

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

    It can be useful only if there's a problem with internet connection. Today using m1/m2/m3 couldn't help as the problem was with judgement system, not the website itself.

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

Well it could be a good round.

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

I think It should be rated or semi rated...all faced the same problem..so I hope it won't be unrated

or the round should be extended

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

I think it must be unrated :( Because we can't see a clearly result of our solution.

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

There's still an hour left! Hope the round will be rated

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

Help me find a word for this...

queue-forces? servers-down-forces??

WTF-is-happening-forces?!?!?!

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

Semi-Rated please !!

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

    How can it be semi-rated? What does it mean?

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

      In semi rated contest the rating change is applied only to the participants with positive change(increase) in their rating. It has been done in past contests.

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

        Thanks for explanation, I didn't know. Yes, it could be a quite good idea.

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

Can't see my submissions, is this my problem? If I submit again, it says "You have submitted exactly the same code before" But I can't see any of them, they're all empty, not even in queue!

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6 years ago, # |
← Rev. 8   Vote: I like it 0 Vote: I do not like it

Just make it fcking semi-rated

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

    It would be unfair for the candidates who solved questions in first attempt to make it unrated, as they deserve their ratings. So better make it Semi-Rated.

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6 years ago, # |
← Rev. 3   Vote: I like it +27 Vote: I do not like it

30 minutes after I submitted my solution, it gave wrong answer verdict. Site is also too slow. Contest must be declared unrated.

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

Such Long Queue !!!!! What the hell :(

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

Is it rated?

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6 years ago, # |
← Rev. 3   Vote: I like it +28 Vote: I do not like it

If the contest goes rated, it would be unfair to those who made a silly mistake in their first submission, and got non-AC verdict more than thirty minutes after the submission. In normal Codeforces round, they would have quickly patched and resubmitted, but now they can't, and the points they would get for resubmitting the problem would be much much lesser than what they could have got generally.

Edit: even after the contest got extended, the above point still holds, and I believe quite a several number of people would be affected by such a situation.

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6 years ago, # |
  Vote: I like it +32 Vote: I do not like it

WTF, make it unrated ..

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

After such a long queue, I don't see any point in keeping this round rated anymore. Even increasing time duration doesn't make any sense.

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

    Also problems C and D are much easier as compared to B.

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

What's the point extending the contest, I've never realized....

How come it would do justice with the inconvenience caused?

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

the problem C lookes just like NOIP2018 Day1 T1 when I hadn't gotten it's meaning

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

Looks like queue is moving. Wonder if it will clear before end of contest.

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

Is the contest extended? It still shows 1hr 15min remaining?

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

QueuedeForces

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

Maybe it should be semi rated that people who waited the queue and got any verdict other than AC it should be unrated for them..and people who waited the queue and got AC it should be rated for them.

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

Man, I got a 'WA' due to long long problems and waited for 30 minutes and received it ! Argh!

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6 years ago, # |
  Vote: I like it +134 Vote: I do not like it

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

Should be unrated. Makes no sense to just extend the round.

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6 years ago, # |
← Rev. 19   Vote: I like it +4 Vote: I do not like it

WA on test case 1 after waiting for like 20 mins xD

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

Extended??

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

Let's not hate on jinlifu1999 too much, he made very interesting problems and the technical issues weren't his fault.

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

    The problems were not interesting! C, D were easier than B which was just a dumb implementation question.

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

unrated. :(

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

The round is UNRATED....

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

I bunked my class for this contest :'(

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

Another emotional story within 15 words . "Due to technical problems, the round will be unrated. We're really sorry about that"

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

    It's a horror story for one who wants to be over a rating of 1600 like me ;-;

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

    this is so sad!!!! :3

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

It's down again...

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

i will never become green :(

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

Anyone remembers round 485? The queue froze down. The same story like in this contests. The round was rated that time. I don't know why don't make it rated too. Codeforces should make these decisions consistently. If that was rated this should also be rated.

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

Story of today's Contest: 1) Submit solution till D in first half hour 2) Wait for verdict on B,C,D 3) Get a wrong/tle 4) Submit a better solution. 5) Be happy because predictor shows increment. 6) Contest goes Unrated. cries in corner

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6 years ago, # |
  Vote: I like it +146 Vote: I do not like it

Guys, sorry about the failed round :( Please, do not downvote the post if you liked the problems. The writer is not responsible for the incident.

This time we faced with the direct actions to break down the testing process. Somebody found an issue in the judging process and exploited vulnerability to make it really slow. I'm working on the fix.

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

    is it related to queues which were there in today's morning?

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

    Why not semi rated??

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

    I know it's not easy at all to keep the system intact especially with the increasing number of participants day after day but it has become very demotivating to play well without any results. We must solve this problem once and for all

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

Why on earth is that there is no hacks?

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

Maybe the problem should be ACDBEF?

I submit a code for problem B in 0:34, and get a Wrong Answer 7 in 1:14.

Then I found that I forget use long long.

Submit and Accept in 1:18.

Wrong Answer = 40min + 50point.

Hope Codeforces will be better.

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

I left codeforces some 2 years ago due to 80% of rounds being declared unrated back then. It was quite unwise to come back and expect something else I suppose.

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

I want to be candidate master In fact. I failed

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

为什么 Codeforces 会在中国春节前出现问题？如果是黑客攻击的话，我感受到了黑客深深的恶意 另外，我本来能涨60分。。。。。。

Why does Codeforces always have problems before the Chinese New Year? If it is a hacker attack, I feel the hacker's deep spite What's more, I could have a rating change for +60

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

    同感! 差這場就紫了 結果... I was about to become purple :(

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

    看老爷子的说法好像是黑客攻击

    According to MikeMirzayanov, Codeforces has(have?) been attacked by a hacker.

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

    傻逼黑客

    shabby hacker

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

I'm really really really sad to face this unrated contest...

It is farther for me to be a master...

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

what's your opinion about not to be rated ?

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

    If it's rated I will -18.

    But if I can get the WRONG ANSWER on time. Maybe I will get a better result?

    who knows.

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

    I will also -18 if it is rated.

    I forgot to add "1ll * " in just one branch of my function in problem B, so maybe I would have better performance if I see WA right after submission.

    It is a really awesome round, seeing it to be unrated is sad, but seems that there's no other choice :(

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

Hello. I can not understand why the round will be unrated? What's the reason?

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

I heard this round is unrated. Is that true?

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

What is wrong with my B. code? Its running fine in PC but showing WA in TC 1 ? How ? I m stuck..

This This This

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6 years ago, # |
  Vote: I like it +23 Vote: I do not like it

When first time solved 5 tasks during contest (if they will pass final tests, of course, but anyway!) and.. it is unrated :D

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

    it was my first time to solve 4 problems within less than 1 hour... sad unrated

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

ALL of my friends had gave up this contest as soon as they got the message that the contest would be unrated.

I lost the only chance to be orange before the Spring Festival.(because if I want to join in other contests I must stay up late.)

I think Codeforces can build an extra judgement system in reserve since this happened more than once.

Sorry for my poor English.And hope Codeforces can become more and more nice.

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6 years ago, # |
  Vote: I like it +97 Vote: I do not like it

.

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6 years ago, # |
← Rev. 2   Vote: I like it -39 Vote: I do not like it

Thanks for contest.

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

Bad day, I stay up late till 22:44(local time). And tell me unrated? However that's alright, I'm in bad state today. So Happy Chinese NEW YEAR everyone!

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

    is 22:44 late?

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

    Lol, you stay up LATE till 22:44 ? What if I say you that THE MOST of the contests for me starts in 00:35/01:35 ? But yesterday round started just in 22:35 :D That is why I took part in it, and... it is unrated :(

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

Problem C was nice, but now I can't stop thinking how could the problem been solved if n could be odd. Any idea?

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

    i think you need only to marge to int then n will be even , but i don't know what is the best two number to marge them maybe it's the two largest number

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

      Try merging the largest number with each of the other number and run the greedy process, then you have an N^2 kind of brutal algorithm, that’s the best I could come up with...

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6 years ago, # |
  Vote: I like it -28 Vote: I do not like it

im so relieved i DDIDNT partisipate ikn this contest... Ive asked multiple times like usual: is it rated is it rated everyoine say IT IS RATED BITCH READ and i say sorry i cant read and then pfaaa mama im actual intellect because now its unrated as i exepcted

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

If its ok to discuss problems now, has anyone else faced WA on pretest 23 for problem E? I can't seem to figure out what might go wrong with the logic.

Upd: Never mind that, silliest implementation mistake. Really worth my handle name.

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

I think this round will be unrated because the system is too slow and there was too many queue

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

How to solve D???

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

    You can do an almost normal BFS traverse, starting from vertex 1.

    The only difference is, to maintain the lowest lexicographically order, instead of storing to-traverse-list of vertices in a queue, we'll store in a MinHeap-based priority queue ;)

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

      why we can't sort adjacent list and start dfs iristran911 ?

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

        This is not enough. I made the same mistake as you ;)

        Take this graph for example:

        5 4
1 2
2 3
2 4
3 5

        So, you start a DFS from 1, which leads to 2, then 3, then 5, then 4.

        However, I can turn back and visit 4 beforehand instead ;)

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

          thanks very much iristran911 ! you are right.I haven't seen it .

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

          Thanks, I was also confused why it is not working

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

    bfs with priority queue (lower node index has higher priority)

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

How to solve F? I reduced it to solving a root of xa = b(% p) , and found no way to solve it.

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

can any one explain B

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

    What can we explain here? It's just a simulation of what's happening in a shop. There's no special algorithm or trick that can be used.

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

C was much easier then A and B

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

LOL seems like problem B & D must change their positions

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

How to solve F? I just find out that we can find the power of fk in fn using matrix exponentiation, but how to solve a congruence system like xa ≡ b (mod 998244353) for x if we know a and b?

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6 years ago, # |
← Rev. 4   Vote: I like it +17 Vote: I do not like it

Here's a proof for C's greedy solution if you are wondering:

1: Groups must be formed as pairs of 2.

Proof: As (a+b)^2 > a^2 + b^2 for positive a, b, we want to minimize group size. As size has to be greater than 1, and N is even, all group sizes must be 2.

Now, we have to pair each number with another such that sum is least. We double this sum. This doubled sum can now be represented as summation (ai + bi)^2 where ai and bi are both permutations of the given numbers.

2: ai and bi must be oppositely ordered sequences

Proof: summation (ai + bi)^2 = summation (ai)^2 + summation (bi)^2 + summation (2*ai*bi); We want to minimize this sum. We observe that the first two terms are constants (sum of squares of all given numbers). So, we want to minimize the 3rd term. This is done when ai and bi are oppositely ordered, proof is a direct application of rearrangement inequality.

Now, observe that this doubled sum corresponds to the pairing where ai is paired with a(N-i+1), with i <= N/2. Thus, we are done.

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

Me waiting after submission. Waiting....... waiting....... One eternity later .......... Fk it, anyways its going to unrated

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

I solved problem B in 30 seconds and wrote its code in 30 minutes :( I think problem B wasn't a good problem for an algorithmic contest. But maybe I'm wrong.

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

    Div2 A/B are rarely algorithmic problems anyway. They're almost always implementation. It's just that the implementation was slightly annoying in this case.

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

Has anyone else faced WA on pretest 21 for problem E?

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

    It might be that you use "set" instead of "multiset".

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

      Um..I have used multiset, but also get WA on pretest21==

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    6 years ago, # ^ |
    ← Rev. 4   Vote: I like it +5 Vote: I do not like it

    If u used multiset, u should erase like multi_set.erase(multi_set.find(x));

    Because erase on multiset is erasing all elements which value is x.

    I did same mistake lol.

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

      Thanks~

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

      Oh yikes really? I wasn't aware that that's how multiset::erase worked. That's unfortunate. Thanks.

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

      Shit, I did this too. I've done this mistake some (long) times ago. Now seems like I forgot this behavior again :(

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

Has anyone else faced WA on test9 for problem E?.... And why I cannot submit my code now.....QAQ

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6 years ago, # |
← Rev. 9   Vote: I like it +58 Vote: I do not like it

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

Make it rated for first 25 minutes when there was no queue.

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

    LOL thats unfair...

    I'm disappointed too because I did well in this contest, but server was not good and we should accept this situation.

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

I see some people didn't like question B. Personally, I didn't mind problem B because it's a straightforward problem that wasn't too tedious to implement (my solution was only 30 lines and can probably be shortened). I think being able to quickly and correctly implement a solution is just as important of a skill as knowing that obscure number theory algorithm that is used in a problem once a decade. Also I think that it's sometimes hard for problem setters to come up with interesting div 2 A and B that aren't just implementation or simple math, but I appreciate their effort in trying.

Some people were also saying that B should have came after C and D. B's solution was just simulating the process (with speedup) and only required knowledge of sorting. C required intuition (need to think to match small with large) while D required graph knowledge, so I think B is more likely to be solved by a someone without experience (i.e. a beginner) than C or D.

Anyway, unfortunate situation with the long queue. Hope next contest goes better.

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

    Agree.

    Simulating can be one of the problem solving skill.

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

What is the solution of F?

I got stuck at counting the number of solutions of the ecuation n^x=y

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

don't blame Codeforces bad things happen:D

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

You owe us one more contest)

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

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

Hey,

Could someone provide me with pointers to why this submission got MLE? https://codeforces.net/contest/1106/submission/49268507

Seems as if most of the people who got an AC did the same thing, except maybe declaring the vectors as global.

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

    You may visit the same node more than once.

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

      I do maintain a list of visited nodes, so that shouldn't be the case.

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

    If the node is already visited you should not push its neighbours in priority queue. Sample :

    8 11
1 2 
2 3 
3 4 
4 1 
1 5 
2 5 
3 5 
4 5 
5 6 
5 7 
5 8

    You are pushing neighbours of 5 four times in priority queue.

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

      Yeah, gotcha. Thanks a lot!

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

1 round unrated after so many contests is surely acceptable.Thanks Codeforces!

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

Whenever I want to gain some rating, the contest will be unrated = = sad story

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

Where is my rating :(

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

In queueueueueueueueueueueue round... How I hope that it can be rated!

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

thanks for the round i really learned something

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

Poor Alice(Expert) and Bob(specialist)!

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