MikeMirzayanov's blog

By MikeMirzayanov, 3 weeks ago, In English,

Hello, Codeforces!

Paul stingray Komkoff is my hero! He found some issues in the network configuration. The most important of them was about flow control auto-negotiation: in case of our network routers the number of dropped packets reduced in times. Thanks!

To be sure that it really helped to fix the issue I ask you to take part in Testing Round #16 (Unrated). It will start on May/07/2020 17:05 (Moscow time). Probably, it will contain 3 easy problems which are not prepared for now (I'll use some old problems, I think). The only reason to host the round is to check the system under a load. It will be an unrated round.

I am upset about what happened with the last round. Once again, I apologize to both the participants and the writer, coordinator and testers. I wrote Monogon about the incident and apologized.

I am sure that the only way to absolutely prevent unrated rounds is just don't host them. And this is not my way. The most popular rounds were hosted without noticeable technical problems. And I'm sure the main records are yet to come. I ask the writers and coordinators to look forward with optimism and try to please us with problems.

Please, join to the testing round. See you!

— Mike.

UPD: Thank you for testing! I think the system worked great. It seems recent reconfiguration improved system performance and stability. We have some rare "Judgement failed" after database update (I'll try to fix them asap).

Announcement of Testing Round #16 (Unrated)
 
 
 
 
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3 weeks ago, # |
  Vote: I like it +72 Vote: I do not like it

Thanks Mr. Mike, for your relentless effort to make this platform better during these harsh times. Hope everything works out.

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

We will gladly participate in the testing round :)

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    3 weeks ago, # ^ |
      Vote: I like it +82 Vote: I do not like it

    It is sad to see that when people need Codeforces, they participate in huge numbers. Yesterday's contest had total of 28k registrations. Now when Codeforces needs people, they just don't bother to contribute as there are only 8.5k registrations till now.

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      3 weeks ago, # ^ |
        Vote: I like it +16 Vote: I do not like it

      just submit each solution multiple times

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      3 weeks ago, # ^ |
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      I am sorry that u feel this way but i did not check my mail until the round was already over. I wanted to be a part of this too :(

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

You can count on me :)

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

It is nice to see that Codeforces community is making some good efforts :)

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3 weeks ago, # |
Rev. 3   Vote: I like it -92 Vote: I do not like it

This quarantine time we expect more contest.Why my comment too much down voted don't understand.

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

    I guess it's because the exact same thing has been said countless times since the quarantine started XD.

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3 weeks ago, # |
Rev. 3   Vote: I like it 0 Vote: I do not like it

Everyone should try to participate. Codeforces is getting better in this quarantine. <3

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    3 weeks ago, # ^ |
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    Make codeforces great again together, <3

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

    did you put this comment for increase your contribution ?

    even you don't submit a single attempt in this testing round .

    tahsin_protik

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

      Give him the benefit of the doubt — he might have had legitimate circumstances.

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      3 weeks ago, # ^ |
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      I didn't have stable Internet connection, I wished to participate! Don't spread negetivity in any community!

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    3 weeks ago, # ^ |
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    yes...it will help us (who are depressed like me)...:')

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

Thanks MikeMirzayanov for your effort and kindness to make this community better!

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3 weeks ago, # |
Rev. 2   Vote: I like it +38 Vote: I do not like it

Feeling sorry for Monogon but gonna remember him for a long time because of the issue :)

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3 weeks ago, # |
Rev. 7   Vote: I like it -23 Vote: I do not like it

Thanks, Mike.

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3 weeks ago, # |
  Vote: I like it +373 Vote: I do not like it

The plot twist is that halfway through, this testing round will become rated when all goes smoothly. :)

In all seriousness, I think this is a great idea, and I wish for upcoming contests to have better luck when it comes to technical problems. I admire your dedication to fix these issues.

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

    Maybe we will have blindfold rounds too in coming future.

    All the submissions will be judged after the contest, give your best shot.

    - An Accidental Invention. (Bug/Limitation when presented as a feature)
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      3 weeks ago, # ^ |
        Vote: I like it -182 Vote: I do not like it

      That's what TopCoder does. Lets shut CodeForces and make TopCoder great again.

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

        are you serious?

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        3 weeks ago, # ^ |
          Vote: I like it +16 Vote: I do not like it

        aryanc where c="chutiya"

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        3 weeks ago, # ^ |
        Rev. 2   Vote: I like it -12 Vote: I do not like it

        ignore him he is mentally retarded .bro look for a doctor in jodhpur. his (aryanc403) most of comments either on codeforces or codechef only makes people sick.

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          3 weeks ago, # ^ |
          Rev. 4   Vote: I like it -59 Vote: I do not like it

          0 My father is a well-known doctor in Jodhpur. Feel free to consult him for me. But next time make sure to do your homework.
          1 Not surprised with back to back comments within 1 min and personal abuse and same no of upvotes. I'm pretty sure the same person operates both accounts and is upvoting himself using his alts. 650iq and saurabhkumarfx
          2 If you were just angered by the fact someone told something to your favourite website then dude gets a life anyone can just come and manipulate you due to your anger.

          Spoiler

          4 "his (aryanc403) most of comments either on codeforces or codechef only makes people sick". My comments are sick but my contribution here is +120 but your both account has -20 each. Much wow. Nice maths. No doubt why your colour is....

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            3 weeks ago, # ^ |
            Rev. 2   Vote: I like it -12 Vote: I do not like it

            that so called out of box thnking made u say both are my accounts?? i am intrigued seeing your maths.But your numbers will fail soon.

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              3 weeks ago, # ^ |
                Vote: I like it -33 Vote: I do not like it
              1. I stated the reasons why I feel so. Learn to read.
              2. Numbers may fail on one comment but cumulative over all comments so far will take months.
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            3 weeks ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            haha..i was expecting this comment of yours about the color. Well your color just shows that you have invested more time in coding than us and nothing else. Secondly, apart from coding try to learn how to live a social life, bcoz from your comments i can surely find out one thing that you got no life bro, go make some friends and be happy.

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

              Ok. :).
              P.S. — I wrote one more thing apart from colour do read that.

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

            do not be ecstatic seeing your color .Just like you said I have many accounts so i might have better color than u on my original accounts on both platform or May be whatever you have achieved or will achieve in your lifetime using your master color some newbie have achieved more than u till now only .(newbie) does not mean to be disrespected or judged because of their talent because they might have different interest and just learning some basics for fun .And i am sure people like u only clear comapanies coding round and get rejected in interviews finally.So learn some other things also. Being master after slogging like u for years does not make sense and does not make u special and many newbie achieved more than u in their fields in less than that time.

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

              ignore him he is mentally retarded .bro look for a doctor in jodhpur. his (aryanc403) most of comments either on codeforces or codechef only makes people sick.

              If you need an anonymous account just to abuse people and get your voice heard. Then let me tell you you are much worse and sick than what you claimed I am. I at least use the same account to say whatever I feel and everyone knows what I am saying and then they use their judgement to make opinions about me.

              I wanted to use one specific word for you —

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

                sure lets assume i am coward .But do not forget atleast i respect my original color and do not use that color to abuse codeforces like u and on the other hand u learned so much from codeforces and urging people to leave this site when it is going through hard time ???? this is what called traitor and u should know traitor is more shameful word than coward. DO not forget u owe significant amount of gratitude to codeforces and u are betraying it after getting your proud color so called "master" which u are by the way using to show your achievements as well.

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

              "Being master after slogging like u for years does not make sense and does not make u special and many newbie achieved more than u in their fields in less than that time."

              What the heck ? Are you saying if someone takes more time to reach a color , he doesn't deserve it?

              Bro , do you even realize how many years most reds have trained to reach their level?

              So now if a prodigy comes and becomes a LGM in just one year from scratch , will that mean other LGMs are worthless ?

              Some more relevant info : aryanc403 has taken ONLY around 3 years to reach so close to red , and you think that's "slogging like u for years" ? Are you fking crazy? How much faster were you expecting him to be ?

              Wait , do you search things like "How to become LGM in one month?" in google? XD

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

                He doesn't deserved a reply. I realised that too late. It's difficult to explain to the kids that some comments are never meant to be taken seriously.

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

                pritishn so if u become master u will judge people based on their color?? will u tell them ""thats why your color is grey""??? why are u taking seriously when whatever aryanc403 said is not serious.Who started fighting of "colors" ?? is it me ?? Bro if that comment is joke then why all other people did not understand that why that is downvoted so badly ? ofc aryanc403 is good in programming but that does not mean u make fun of people because of their color when u do not know even their true color

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

          And I got equal no of downvote on it within the same duration. Wow. One more comment just to get more downvotes from your alts.

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

      Thanks but No.

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

    Unlucky that your round was unrated. I really enjoyed the problemset!

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

Is this test need i crazy submit but not must be "accepted" ?

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

    I think yes. It's just testing the codeforces system.

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3 weeks ago, # |
  Vote: I like it +146 Vote: I do not like it

Monogon's problems were really a bit different and so interesting. I'll be waiting for problems from him.

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3 weeks ago, # |
  Vote: I like it +60 Vote: I do not like it

Is it possible to write some stress test for CodeForces? The test could be like:

  • Open up a fake contest, only for bots
  • Spin up ~1000 docker instances, each hosting one bot
  • The bot submits a bunch of code at various random times, see how the server handles it

Ideally, I think we could run this test 1 hour before every rated round and immediately know if there are issues with taking too much load. This should make it possible to detect when the site is unstable and give us a chance to postpone rated rounds.

I'm sure there are many bored devs (like myself) that could code this up in a few weeks :)

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    3 weeks ago, # ^ |
      Vote: I like it +86 Vote: I do not like it

    Mike actually has quite a few stress tests, but in this case it didn't help because the issue has only manifested itself recently and it was likely triggered by some other machine on the same network (or even a misbehaving network switch). Fortunately now we know which metric to monitor and we won't be surprised by a sudden failure of this kind.

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

Thanks MikeMirzayanov for your problems.

They are very interesting.

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

    Sure mike we r with you! Hoping for more intresting problems!

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

Was waiting for that "The rounds must go on" line, I have to say i am disappointed.

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

Hope that Round 640 won't be unrated. If both of the current rounds were rated, I'd have been 2700 :(

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

    As an author I'd also like to see everything is fine. But in fact we are considering delaying the round if such issues may probably happen again in the near future. XD

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

    The simple fact that these rounds were unrated makes their results unreliable. I've also had some great results when enough people decided not to bother competing.

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

We should participate in large numbers in testing round and make codeforces great again. Good Luck!

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

Thanks Mr.Mike again,we will glad to participate this testing rounds,and wish the codeforces better and better.

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

Mike, thank you all the time. We woule love to do that. Hooray

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

Codeforces Round #639 (Div. 2) really deserves to be rated :)

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

Sometimes shits happen like this but it's really a demotivation to the problem setters. Still Who knew something like this will occur :( Hope the testing round ends up well enough

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

Why am I seeing so less registrations? Because I think we had no problems upto 10k registrations. So until more than 15k registrations are there , I don't think we will really be testing codeforces' vulnerability. So please do participate.

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

Hmm.... Testing round would love to be part of it Mike. Thank You for putting so much efforts...

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

Will gladly participate! Thanks a lot for this amazing platform Mike!

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

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3 weeks ago, # |
  Vote: I like it +315 Vote: I do not like it

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    3 weeks ago, # ^ |
    Rev. 2   Vote: I like it -7 Vote: I do not like it

    ok

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

    What is the film that this meme template is from? (thank you in advance)

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

      Person of Interest, episode 4x10 — The Cold War

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

    As a huge Person of Interest fan, I approve of this comment.

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

Guys, please, help me with this problem.

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

It would have been better with 4 problems equivalent to div2 B, C, D, E, I think. Anyway, will participate in the testing round

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

    I think for testing it would be better to have all problems pretty simple like div2A or even Div3A as the target is not to compete but to stress test with many submissions. If you add harder problems you would get smaller queue which is not the target of stress testing!

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

This testing round deserves more than 15k participants, just like what normal div2 rounds do these days, or the testing result won't be much persuasive. Everyone looks forwards a better Codeforces, especially my friends and I, who has made an effort on preparing Round #640. So please register for the testing round if you can. Hope everything the best!

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

What is the reason for Judgement failure

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

Happy to participate in the Contest. Will the First question be Watermelon ;-)

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

    Turns out it is not as difficult as you mentioned.

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

If this is because of server load, maybe CF can start to limit the number of participants to something like 15k participants. I am not sure but I think TopCoder also limits the number of registrations for contests to a small amount.

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

    If stress test is what Mike is going for, I think "the more, the merrier"!

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

      I was not talking about the testing round, but contests in general.

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3 weeks ago, # |
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Thanks mike for your effort by providing such a beautifull platform for competitive programming. Although i suggest you should see for the matter of excess crowding on site while rated contest to respect the efforts of contenders and contest organisers. one of my suggestion is -you should close all other activities on site while official rated contest is running.

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

Let's be the part of the history by our spontaneous participation and make Codeforces great again! Thanks Mr. Mike for your effort.

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

It was actually frustrating for us when we saw the big queue during contest time even though this contest was delayed for fixing bugs. Still hats off to your effort CF team. Hoepfully today's contest will be a smooth one!

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

keep calm and submit a code

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

Thanks to Monogon for the round. The tasks were very interesting. I hope everything will be fine next time

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

After increasing the participant of div-2 & 3 (24K to 26K ) cf might update their server request bacause before 2/3 month cf have only 16k/17k participants, now its time to upgrade cf server

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

    I'm sure they never considered this...

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

Is it just me or the world is getting crazier out there :) Edit- It was just a joke and no offense intended to anyone. I greatly appreciate the author of codeforces to give us such a brilliant platform to code and for creating such a helpful community.

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3 weeks ago, # |
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Expect no problem again .

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

I will participate too.. and try submitting like crazy.

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3 weeks ago, # |
  Vote: I like it -31 Vote: I do not like it

I hope that after fixing the problem, Codeforces will create more contests, as a compensation for Codeforces lovers. Div3 is a good idea right?

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3 weeks ago, # |
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Never fear !! The vizard is here All the best for the round.

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

If you can,Please register so that codeforces can find the problems and solve them.

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

MikeMirzayanov if you wanna check the extreme case put at least 1st problem easiest. Kind of "sum of two numbers" or something like this so that everyone submit it instantaneously within seconds and hence it will result in largest overloaded queue possible.

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

would like to thanks to Mr, Mike for his efforts in last round and i appreciate the idea about 1 hour unrated contest. I will surely take part in this contest.

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

Thanks Mike for this wonderful platform and your efforts to make it better.

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

I think this contest should have as most participants as possible. If so then the testing round will be successful and Mike can be sure that It is okay now.

so participation is our responsibility now.

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

HEY FOLKS WHAT İS 7K REGİSTERED ?? We have to increase this much more and be a lot of people (like regular rounds) otherwise the testing round has no meaning, right?

let's wake up and attack the judging. let's see has it fixed? I hope it has improved Thanks MikeMirzayanov for your strive, although if it has not improved!

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3 weeks ago, # |
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To make up for the low participation I suggest we all spam submit with any code every minute lol

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3 weeks ago, # |
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That sounds great. I hope Codeforces is getting better and better.

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

I felt bad for you. During every contest in this quarantine something bug issue came. Hope this time there is going to be everything solved! Good luck.

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3 weeks ago, # |
  Vote: I like it +50 Vote: I do not like it

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

I'll try to enter Guinness records for 'the most submissions in one Codeforces round' .

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

The only reason to host the round is to check the system under a load.

I hope there will be a load or it won't test much.

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

    Exactly, I expected to see easy problems with large input or large amount of processing needed, with lots, perhaps hundreds of test cases. Instead, we got three problems with a trivial amount of processing. This round didn't test anything.

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

Making more submissions, would you like to join me in the coding challenge without compiling? Just thinking is interesting!

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3 weeks ago, # |
Rev. 4   Vote: I like it -6 Vote: I do not like it

Very few registrations in comparison to last round! Where are the rest of the participants who felt bad for the last round? :(

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

Hope test round will be successful. It is beneficial for both sides. Because no problem setter wants their round to get through troubles and no participant wants their preparation to go in vain. All the best.

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

That testing round should have been hosted before round 639

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3 weeks ago, # |
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I'm a bit disappointed by the small number of registrations, because if we don't try it out now, it might happen again in another rated round.

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

Please submit lots of submissions, this would make this contest have a high load, and get better results.

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    3 weeks ago, # ^ |
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    Yeah I think its the only way now, I thought more people would participate :(

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

This is the only round where my code has a lot of bugs is useful :D

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3 weeks ago, # |
  Vote: I like it -33 Vote: I do not like it

Is it rated?

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

is rating contest?

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

Please provide ranks though.

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3 weeks ago, # |
  Vote: I like it +72 Vote: I do not like it

Probably it would have made sense to add much more problems (even simpler ones), so that even a relatively low number of participants could generate lots of sumbissions.

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

Im so happy that everything works great! Congratulations!

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

As it is a testing contest so we should make a worst case(a lot of submission) :)

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

Thanks for the contest <3

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3 weeks ago, # |
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Locked problem but cannot see others code. I am trying to hack. Should I hack blindly?

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

This could've been a cute div3.

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    3 weeks ago, # ^ |
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    i think too easy even for div 3. but yes, B and C were pretty nice!

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3 weeks ago, # |
  Vote: I like it -13 Vote: I do not like it

I solved all problems, cant we make it rated?

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

Anyone else or just me who received "Judgement Failed" verdict in problem C and suddenly after a minute or two it changed to "Wrong answer on test 2" ?

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

Althogh i solved all problems, but CF predictor tell me that my rating will go down. X:) (just for fun)

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3 weeks ago, # |
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So on the bright side , codeforces will work better than ever now?

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3 weeks ago, # |
  Vote: I like it +84 Vote: I do not like it

How to solve A? I think it had something to do with FFT but I couldn't get anywhere

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    3 weeks ago, # ^ |
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    You should try DP and Shortest Path,as well as segment tree and etc.

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

    Well, FFT is definitely not enough in this case. Try transforming it into a graph problem and then finding some flows.

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    3 weeks ago, # ^ |
      Vote: I like it -65 Vote: I do not like it

    i guess a + b will do the job

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    3 weeks ago, # ^ |
      Vote: I like it -37 Vote: I do not like it

    Hint: Use '+' operator.

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

    I think you got it wrong it was to be done by convex hull trick with matroid transform

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

    I solved it using squirtle watergun algorithm

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

    Can be solved using segment tree of tries. Good luck!

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

    About which problem are you talking bro ?

    I'm sure you're not talking about problem A of this testing round...

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    3 weeks ago, # ^ |
    Rev. 2   Vote: I like it +44 Vote: I do not like it

    This is a tough one.

    Let dp[i][j] be i + j. Then dp[i][j] = dp[i-1][j-1] + 2.

    Another solution is to observe that add(a, b) = add(a, b-1) + 1 and so you can solve the problem recursively.

    I can't think of any solutions simpler than that.

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

    Are u serious? I think fft is overkilled here. I used 2 arrays to store a and b in binary base. Then just simply did greedy.

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    3 weeks ago, # ^ |
      Vote: I like it +17 Vote: I do not like it

    Got AC with wavelet tree.

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

    You can also do Matrix Multiplication for a simple solution. https://codeforces.com/contest/1351/submission/79303363

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

    Well constraints were too tight I think machine learning can do some good....

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

    Prob A was meant only for Red coders. Don't waste your time on it. I am waiting for its tutorial...xD

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3 weeks ago, # |
Rev. 6   Vote: I like it -10 Vote: I do not like it

Problems were good.

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

Judging System got slow again at the last minute?

UPD : it's ok now

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

How to do C?

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    3 weeks ago, # ^ |
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    Maintain which point you came from and where you went for every move, store them in a set to check for repetitive.

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

      Hi! I solved it after the contest but can you help me if my logic is right? I made pair of each and every point I have already visited and store it in a set. Then I check if destination point is in the set. Is this the right approach?

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

        That was my solution initially, and it is wrong. The problem asks to check for visited segments, instead of points. So if you went from (0, 0) to (1, 0), and then at some point went from (2, 0) to (1, 0), these two are considered different segments and take 5 seconds each, although they share the same destination.

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

        Try taking a map<pair<int,int>,set< char >>m... store the visited points in pair<int,int> and the direction from which it is visited in set< char >. Then see if your destination point is in the map as well as check if it was visited from that direction ...hope that helps...

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

          there are 4 directions to come at a point but this set will only be able to store one

          how to check that then?? thanks in advance

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

          Thanks! That is an amazing approach with a minor modification. I just hardcored the solution by making a set of pairs of start and destination and destination points. Something like set<pair<int,int>,pair<int,int>>. Then I just check if the current start and destination points exist in the set as (start,destination) or (destination,start). I was not familiar with pairs till now but figured it out after the contest. Here is a reference to my solution.

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            3 weeks ago, # ^ |
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            No need to thank me....we are all here to help each other out.

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      3 weeks ago, # ^ |
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      Can you check what is wrong in my solution https://codeforces.com/contest/1351/submission/79353675

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

        Try this: WNES

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          3 weeks ago, # ^ |
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          Works fine, gives 25 as expected

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

            The correct answer is 20, and I was expecting your code to give 16 hmm

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3 weeks ago, # |
  Vote: I like it +63 Vote: I do not like it

When will the editorial be available xD?

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    3 weeks ago, # ^ |
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    I m wondering what would be the editorial for prob A..xD

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3 weeks ago, # |
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How to solve c? What is the concept used

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

    You need to store tuple of four values (fromX, fromY, toX, toY) in a set, when you insert a new tuple but it already existed time++ otherwise time+=5.

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3 weeks ago, # |
  Vote: I like it +57 Vote: I do not like it

So, this is a testing round for the feasibility of div.4 round?

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

Will CF round 639(div 2) be added in account like others round?

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

IS codeforces running in a cloud server? If that the case, why not scale-up the resources?

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

Please make this round rated.

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

    No.

    It's possible to make a rated round unrated, but impossible to make an unrated round rated.

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

      It is possible but that will not be fair.

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3 weeks ago, # |
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Can't I submit the solutions again after contest?

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

How to solve B?

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

    Just add non-equal sides of two rectangles and see if it matches the other side of rectangle.
    Eg. l1=3,b1=1 and l2=3,b2=2 (l1,b1 = length and breadth of 1st rectangle ans so on)
    so check b2+b1 == l1
    In other words if summation of two different sides of rectangles should be equal to size same as the common side of rectangle.

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

    For a square $$$a \times a$$$, it will split into two pieces after the operation. Let's assume that the size of them are $$$x \times a$$$ and $$$y \times a$$$. Notice that $$$x+y=a$$$ and $$$x<a, y<a$$$. So the greater one in each pair should be equal. And the sum of the smaller one is equal to the greater one.

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

    There is always a common point(Hight or width) between those two rectangles. You have to find it(point) out. If it's SQUARE is equal to the Summation of the AREA of two rectangles then it's OK or NOT. My solution for B..79297732

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

    max(a,b) == max (c,d) && a + b + c + d == 3*max(a,b)

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

When is the next div 3 contest? I want to participate and I wnat problems for my level!

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    3 weeks ago, # ^ |
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    You can always practice with the problemset if you wanna get better, it's not all about the contests but rather the learning :P

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

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

    When your only contribution on CF is because of the memes you upload.

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

Why where the problems so hard?

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

I think CF can provide a simple trial problem before each rated round like 3-4 mins before. If you want to participate, you have to solve that problem. This would lead to a lot of solutions before the start of the contest. Now during this time if there is a queue, they can decide whether to hold the contest or not. I mean this would at-least ensure that the efforts of the problem setters do not go to waste.

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

Where is editorial? I am waiting for it.

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

has codeforces round 640 just been cancelled?

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3 weeks ago, # |
Rev. 2   Vote: I like it +24 Vote: I do not like it

Capture
I've just noticed that 'CF round 640' has been removed from the list. What's the plan? We all want to have a rated round shortly :|

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

Please release tutorials lol

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

hey tourist, you better register.

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

does anyone has the solution for the C problem ? i tried to solve but my solution seem not to be right!

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

    Right after reading C, I came up with your solution too. It is actually pair<pair, pair> not only pair. Instead of just using set<pair<int,int>>, u may need to use set<pair<pair,pair>>

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      3 weeks ago, # ^ |
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      i've seen your code ! but i confuseed and dont understand why we would use that pair<pair, pair> :<

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

        We need to store pair of pairs because we need to store the paths visited instead of just points. Why? Take a testcase WNES. Storing only points will result into answer 16 as you have already visited point (0,0). This is wrong. The correct answer is 20. The path is (0,0)->(1,0)->(1,1)->(0,1)->(0,0). You can see that all the paths are visited only once and hence the answer is 20. Hope it helps!

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          3 weeks ago, # ^ |
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          ohh , i got it thanks so much

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

      Since after each move either coordinate of the skier changes at most by 1, the pair of consecutive coordinates (either horizontal or vertical) is uniquely defined by their sum (if the sum is even then the coordinate have note changed, if it is odd then there is a unique pair of consecutive integers with the given sum).

      Furthermore, by scaling one of the coordinates by a factor $$$>=10^5$$$ we can represent the pair with a single (long long) integer.

      https://codeforces.com/contest/1351/submission/79443118

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

Can someone help what is wrong in my solution for the problem C https://codeforces.com/contest/1351/submission/79353675

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

Here's my solutions with explanations. https://github.com/wingkwong/codeforces/tree/master/1351

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

Screenshot-2

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

 Imagine cheating in a VC just to compete for 2nd place if a person checks "show unofficial"... On a testing round.

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3 weeks ago, # |
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where is the editorial?

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

can anyone help me in skier problem my solution: https://codeforces.com/contest/1351/submission/80032861

i am not able to see the testcase in which i am getting wrong answer.