Gerald's blog

Coder-Strike 2014 — Finals
By Gerald, 11 years ago, translation, In English

Good evening!

The final contest of Coder-Strike 2014 will be started tomorrow at 16:00 MSK. The problems (as in previous Coder-Strike 2014 rounds) are prepared by: Gerald, HolkinPV, Igor_Kudryashov.

And we have good news for you. There are two rated online rounds related to the contest: one round for the first division participants and the other for the second division participants. Of course, we've added simple problems in the second division contest (and also deleted hard problems).

The registration for the contest will start at 4:00 MSK, as usual registration ends 5 minutes before the contest start. The first division participants should register on "Coder-Strike 2014 — Finals (online edition, Div. 1)", the second division participants should register on "Coder-Strike 2014 — Finals (online edition, Div. 2)".

Hope the problems will be nice for you, we are really tried our best to prepare them.

Good luck!

UPD. Due to the holding the onsite competition of Coder-Strike 2014, we have to restrict access to the site after the contest. Approximately, the site will be unavailable for 15-30 minutes after the end of the contest.

The editorial is now available.

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Comments Comments (139)
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11 years ago, # |
← Rev. 2   Vote: I like it +4 Vote: I do not like it

Why are there 3 contests pending? Is the 3rd one dedicated to on-site participants? Edit: What's wrong with asking for a clarification about something everybody wants to know better about?

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11 years ago, # |
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What is the duration of the contest?

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

    As always, 2 hours.

    Contests --> current or upcoming contests !

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      11 years ago, # ^ |
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      Thanks, it was not posted when I wrote this.

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11 years ago, # |
← Rev. 2   Vote: I like it -7 Vote: I do not like it

Will the online version be rated ? EDIT : Sorry for having not seen the announcement of Round 2 >_<

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11 years ago, # |
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Will the level of the problems will be same as the normal rounds of codeforces (or even round 1 of coder strike). Are they gonna be harder? I'm talking about div 2.

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    11 years ago, # ^ |
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    They will probably be quite the same. It is said:"Of course, we've added simple problems in the second division contest (and also deleted hard problems)." So, yes, I think they will be the same difficulty as usual for div2 :D

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

Will practice session be unrated for all participants?

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

    Practice session is only for the onsiters. For sure, it will be unrated.

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

Before 20 minuets I saw that "Coder-Strike 2014 — Finals" duration is 25 minuets. But now I am seeing that it is 2 hours. Why? Has the duration changed or I was wrong?

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

    I think that 25 minutes is the duration for Coder-strike 2014-Finals(practice session) The real contest will have 2 hours :) Maybe you have seen it wrong...

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

The contest is delayed by 15min?

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

Is anyone else having trouble clicking on the "Contests" tab? I am getting "This webpage has a redirect loop" on Google Chrome.

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

Again and again delay!! x-( x-(

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

delay 30 minutes !!!!

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

    new time is 4:15..... be updated or u will get 10 minutes penalty!! :)

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

Why are u delaying this??? Have any reason? 4:00 --> 4:15 -->4:20 and now 4:25 Stop doing it! Start the contest!!!

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

Don't delay any more cause I will leave at 17:20 (21:20 here at China) and go to sleep...

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11 years ago, # |
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"Contest has been finished" :P

I even haven't started yet!

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    11 years ago, # ^ |
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    The practice round has ended, that's true for sure.

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

    that was the practice session. even i initially thought like u, but when i saw the timer of practice contest as 00:00:00, i guessed this must be the meaning.

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

3 contests are gonna start at the same time! Hope that the website won't be down.

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

-"Contest is over, would you like to see the results?"

-"Yes"

-"You are not allowed to view the contest" :|

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11 years ago, # |
  Vote: I like it -51 Vote: I do not like it

Help provided by organizers during contest .. .12757 A 22.04.2014 16:39:05 What kind of unhelpful attitude is this? No comments 12756 A 22.04.2014 16:39:04 What kind of unhelpful attitude is this? No comments 12749 A 22.04.2014 16:29:11 Problem not available in English Without Google Translate? Input Converted to getting dates After Translation Please Look into it. No comments 12748 A 22.04.2014 16:29:11 Problem not available in English Without Google Translate? Input Converted to getting dates After Translation Please Look into it. No comments 12746 A 22.04.2014 16:28:43 Problem not available in English with Google Translate? Input getting converted to dates after translation please look into it. No comments

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

    If you're complaining about something, write properly what it is. All you're doing is giving random (from the POV of anyone who doesn't know what you mean beforehand) numbers, dates/times (why point out today's date, anyway?) and repeating sentences.

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

Many people solved problem A within one minute, and got 500 pts!

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    11 years ago, # ^ |
      Vote: I like it +57 Vote: I do not like it

    They probably have reading and coding speed over 9000. rares.buhai read and solved in 5 seconds.

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

      I think he cheated. He might have known the problem.

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

        Actually I solved it in 0 minutes as well. It looks like the timer started later than the problems became available. So I've seen the problem, written the code and submitted it and then I saw that it show that there ~1 hour 59 minutes left in the contest. I see that my local file was modified at 16:19 MSK, 4 minutes after the contest started, not sure why it was counted as 0 minutes.

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

          This is because of my mistake. We have a lot of movements on the onsite, and I've made a mistake while changing time of the first division contest.

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

            So,the actual duration is 2hours & 4minutes?

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              11 years ago, # ^ |
                Vote: I like it -51 Vote: I do not like it

              Seems so. This should be unrated based on precedent — in some not very old contest on CF, sone people had access to the problems because of a bug, and it was unrated. This is almost the same situation.

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

                Yeah, I can remember that, same situation .... but that doesn't make this same round need to be unrated

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

                  it seems both of you will loose rating if it is rated :P

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

                  I probably will, but not much (I lost a lot last time and got a better place now). I might even gain a bit, but that people could submit at 0 minutes bugs me anyway.

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

                I thought today everybody had access to problems 4 minutes before the timer started.

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

                  But not everybody knew. I only read the problem when the timer said that trying wouldn't be a waste of time. There are better things to do before a contest than holding F5.

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

                  Well, I was online at the point when the round started and I got a notification that round has started asking whether I want to proceed to to the problems. And I didn't notice the timer issue until I have already submitted the first problem. Are you saying that you didn't got the notification?

                  I'm quite happy to see it was rated even though my rating declined back, that's what I earned in this contest.

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

                  AFAIK the notification showed for me at the supposed start time, not 4 minutes earlier.

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                  11 years ago, # ^ |
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                  And that seems to be exactly the time we started. We didn't start BEFORE the supposed time (16:15 MSK), the timer started later. Strange thing is that you look into my and your attempts it seems to show the correct time for both of us — you seem to submit the problem one minute earlier than me. But mine is counted as 500 points (first minute of contest) and yours is counted as 494 points (forth minute of contest). So I suppose the timer was tweaked between our attempts were made and the only thing required to make these results absolutely fair is to recalculate the points given to each contestant for each problem.

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

                  That'd be good, then. It'd also be nice to get an opinion of someone who can see into the system.

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

          I wonder what would have happened if somebody submitted before the timer started... more than 500 points? :D

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

    Div 1 contest started 4 minutes after div 2 contest. I think they cheated

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

Div2 D , wrong ans on pretest 5 :(. my idea was : for each i , if(freq[i]>=p)res+=(n-1); else { for each j=p-freq[i] to n res+=(number of numbers that exists j times) if(freq[i]>=p-freq[i])res-- } res/=2

is it a wrong idea? [freq[i] means frequency of i, how many coders have voted i]

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    11 years ago, # ^ |
    ← Rev. 5   Vote: I like it 0 Vote: I do not like it

    Perhaps I misunderstand you, but a programmer does not agree twice with his choices. For example if we have 

    5 3
1 2
2 3
4 5

    Then answer should not count (1,2) even though the pair (1,2) has frequency 3 — the first coder can only agree once.

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

      Thanks a lot, You saved my lots of time of mine. You exactly got my Bug. thanks again.

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

    If test is like 4 4 3 4 3 4 1 2 1 2, you cannot choose (1,2) or (3,4) because of only two coders agreed with it. I suppose.

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

Thumbs down for a contest starting at past 19 minutes. I had just finished D when I saw the contest ended at past 19 minutes. This is said in a constructive way, I'm sure this confused a lot of coders.

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

If site access needed to be blocked couldn't you have at least run system testing while we waited :(

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

why there is no register for practice button?

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

Only 5 pretests for problem C .....:(

EDIT: Strange thing: Same problem in div 2 ( Problem D ) has 7 pretests...!

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

    Only 5 pretests for E. It's as effective as blind submissions.

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

    It was div 1's problem C :)
    How did you count pretests??!

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

      Look at the "Status" page. Check the nearest "failed test #x" and "failed pretest #y".

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

      A.Some coders got "Wrong answer of pretest 5" during the contest
      B.lots of coders got "Wrong answer of test 6" after systest

      A, B => There were 5 pretests for C
      :D

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

        No I said that about div 2 D.
        A.Maximum number of WA on "pretest" was 7
        B.Minimum number of WA on "test" was 11
        How did you found that it had 7 pretests?!!

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

Problem D of Div 2 was really interesting!

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

Problem B is the kind of problem that only looks very easy and in fact requires a very creative idea. Is anybody available to give a little hint? Don't spoil it all (yet), please.

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

    Remember a set of all possible leaders (everyone can be a leader at the beginning) and update it as you process the queries.

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

    Here are some observations

    Participants who haven't participated in the log in/off operations all can be leaders.

    From the remaining participants ... there can't be more than one leader from them.

    Whenever a participant log in/off and there are other participants already logged in, then he can't be a leader.

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

Why can't I see other people's solutions yet?

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

system test is quite fast...But how long does the rating update?

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

    about 30 mins has passed since the system testing has ended. I don't know why the rating are not updating...

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      11 years ago, # ^ |
        Vote: I like it -35 Vote: I do not like it

      Maybe because there's the question of whether they should be updated at all. Something's seriously wrong when there are 5 second submissions.

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

        I am afraid this contest will be unrated... because the div1 is started later than div2.... and it seems rating was not updated until now...

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          11 years ago, # ^ |
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          But that doesn't change anything for Div2, does it?

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            11 years ago, # ^ |
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            Yes....actually what I want to know is how to do with this mistake...

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

How is it possible to hack without submitting a solution? See picture. Was checking the tail end to see how many people actually submitted anything and came across this.

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

    My guess would be: submit a problem, lock it, make a hack and then get your submission banned by the cheater detection system.

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      11 years ago, # ^ |
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      Yes...his or her A and B submissions were skipped....

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

      Ahhh, that's exactly what happened (submission history shows skipped submissions for him). Thanks! :)

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

    If you actually check his submission history, you will find that he did made submissions but for some reason these submissions are skipped and hence not shown in the standing list.

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

Why it took so much to be able to run practice?I have 2 sources ready to be submit and I'm very anxious to see if they work...

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

When will the ratings be updated ???

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11 years ago, # |
← Rev. 2   Vote: I like it +44 Vote: I do not like it

A humble request to codeforces' admins, please don't make this round unrated.

-On behalf of all participants who did better than usual.

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

    and the other half are worse than usual :(

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

    I think there is no strong logical reason for the contest to be unrated!
    Don't worry!

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11 years ago, # |
  Vote: I like it +59 Vote: I do not like it

Please make it rated.

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

    in contest 234 Div 2, Problem B changed to another one, after 1 hour of contest. and contest was rated ! I think this contest will be rated !

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

      That affected all participants equally. Wrong timer gives an advantage to people who tried to read the problems before the contest started.

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

        Sorry but you are wrong !

        In that contest, many of people had a wrong algorithm for first type of problem and got accepted ! (when problem changed, they algorithm became correct)

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

          It's interesting that I understood the problem correctly. I remember that one, choosing "some" didn't make sense to me based on something (samples? problem difficulty?), so I chose the best meaning I could find at the spur of the moment.

          Problem reading skills are also part of competitive programming skills. Trying to open problems early on or being given a random advantage by the contest system are not skills at all.

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

          yeah i remember that contest!
          i wrongly interpreted the original (incorrect) problem as though it was the modified (correct) one, and got AC! :D

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

        I got the prompt from codeforces stating that the contest has begun and I clicked ok which took me to problem A. So did I get those extra 4 minutes or not?

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

          Well, I also got it, but only in the regular time. So probably not.

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

Here is the email I just got :) ________________________________________________________________________________________________

Hello, VeniVidiVici.

The final contest of Coder-Strike 2014 will be started soon! Top highschool children from Moscow will meet in the CROC office.

Codeforces will host online rounds based on problems of Coder-Strike 2014 Finals.

I'm glad to invite you to take part in Coder-Strike 2014 — Finals. Actually it will be two separate online rounds: for Div. 1 and Div. 2. It starts on Tuesday, April, 22, 2014 12:00 (UTC). The contest duration is 2 hours. The allowed programming languages are C/C++, Pascal, Java, C#, Python, Ruby, PHP, Haskell, Scala, OCaml, Go, D and JavaScript.

It will be rated events for all the participants. Do not miss the round!

The round will be held on the rules of Codeforces, so read the rules (here and here) beforehand.

Want to compete? Do not forget to register for the contest and check your handle on the registrants page. The registration will be closed 5 minutes before the contest.

If you have any questions, please feel free to ask me on the pages of Codeforces. If you no longer wish to receive these emails, click — to unsubscribe.

Coder-Strike Team ________________________________________________________________________________________________

This might have been a little late :P

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

Why there is no virtual participation?

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11 years ago, # |
  Vote: I like it -30 Vote: I do not like it

unrated?怎么还不更新啊T_T

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

Post have been edited:
UPD. System was a bit sleepy and went to sleep. Maybe tomorrow it will update ratings. Have a good night!
:D

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

When is this contest going to be rated? There is no update in the blog post and no one has said anything. More than an hour has passed since the system testing phase has ended! Any idea?

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

At least for me the ratings are updated — I join the ranks of the first division today!

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

Ratings have been updated. Got +132!!!!

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

1948->1894...the numbers is the same,but the order of them is different...Good night Codeforces.

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

at me it remained exactly the same: 1700 is that really the correct rating or is there a problem?

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

    It means you do just the same as the system predicted according your rating during the contest...

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

    Wow!!!
    Two consecutive 1700 as rating!
    Really cool :)

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

      what makes it even cooler is that 1700 is exactly the border of Div-1 and Div-2!

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

Nice problem statements.Easy to understand...

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

I can't solve 2day's problems after the contest !

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

I haven't understood the problem Div1 B's Sample.

For Sample #4:

5 6
+ 1
- 1
- 3
+ 3
+ 4
- 4

3 is an output.

For sample #5:

2 4
+ 1
- 2
+ 2
- 1

why 2 is not an output ?

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

    Because 2 must be in the chat while 1 is in.

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    11 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it 
    + 1 -> 1, 2
- 2 -> 1
+ 2 -> 1, 2
- 1 -> 2
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      11 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      For sample #4 for it will be these, right?

      • 1 -> 1,2,3,5
      • 1 -> 2,3,5
      • 3 -> 2,5
      • 3 -> 2,3,5
      • 4 -> 2,3,4,5
      • 4 -> 2,3,5

      3 is not always present ? right ? so how come 3 is an output for sample 4

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

        We have no information for 5 and 2, so they can totally be absent all the time. When that happens, the 3rd slot have 0 present member and hence not counted for checking.

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

        We must consider the following case.

        + 1 -> 1, 3
- 1 -> 3
- 3 -> nobody
+ 3 -> 3
+ 4 -> 3, 4
- 4 -> 3
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11 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

How to solve Problem C? (Div2 — Online Meeting)

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

    I think explanation above inspiring enough.

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11 years ago, # |
← Rev. 2   Vote: I like it +20 Vote: I do not like it

will there be any editorial published for this round?

EDIT: it's now published. here is the link. :)

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