Ripatti's blog

By Ripatti, 7 years ago, translation, In English,

Hi all!

That's the 150th (anniversary?) Codeforces Round. For the 1st and the 2nd divisions both.

Round is prepared by Ripatti , Gerald , Delinur .

Enjoy!

UPD. Points are standard: 500-1000-1500-2000-2500 for both divisions.

UPD2. Contest complete. Cheaters are deleted. Ratings are updated.

Div1 winners:
1. scottai1
2. vepifanov
3. rng_58
4. Egor
5. Komaki

Div2 winners:
1. mochavic
2. JKi
3. mfv
4. pavel1996
5. TangJie

Thank you for your participation. Come again.

Editorial will be tomorrow.

UPD3. Editorial. Sorry for delay.

 
 
 
 
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7 years ago, # |
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I hope problems will be as good as contest number :)

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What a short post! Great!!

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    7 years ago, # ^ |
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    haha :D

    What the 157 symbols!

    So being shorter means being great?

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      7 years ago, # ^ |
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      Take it easy please. I just said that it was not like the others. :)

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7 years ago, # |
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Why is 150 a good number?

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    7 years ago, # ^ |
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    There's no accounting for taste.

    But probably beause we still think of numbers decimally.

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ill hope it will be good contest like last

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7 years ago, # |
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I wanna pass a vector as a reference to a function. can anybody help me??? template code or helping links pls.

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7 years ago, # |
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Will the problems be sorted by order of difficulty? What is the scoring system gonna be??

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Good Luck!!!

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7 years ago, # |
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all you guys be cool like me !!

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7 years ago, # |
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My contribution is positive. What did I do? o.O

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7 years ago, # |
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Good luck & have fun !

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7 years ago, # |
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Amazing anniversary :-ss I have never a problems like Div 1.A Amazing or bitwise

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7 years ago, # |
  Vote: I like it +77 Vote: I do not like it

Seriously, why? Not enough servers? 'Shut down all the servers' button was clicked by an accident? Slow code? Strange Java behavior? 'The load was so high that we were not ready for it?'

It looks very strange and unnaturaly for me; CF rounds are not beta for a long time and there are still problems sometimes.

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    7 years ago, # ^ |
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    sorry to say that but if the server isn't strong enough just limit a registration number : )

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7 years ago, # |
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mnlfrnnds04 has 24 hacks so far, all of them on the same person. With 1 correct task he is third. Seems legit...

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    7 years ago, # ^ |
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    He is very lucky that stay in chicky room, and he got crazy number of successful hacking attempt. Congratulation! =]]

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      7 years ago, # ^ |
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      look at their profiles. same photos, same countries, a little bit alike nicknames. that's obvious...

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        7 years ago, # ^ |
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        What is his room ??? anyone in his room please tell my some information abou this case please :D

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        7 years ago, # ^ |
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        obvious cheater is obvious :d

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    7 years ago, # ^ |
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    Yes. now they are 26. The both users are have equal avatar. "Nothing suspicious" :D. And the oth users are from Turkey. Again "Nothing suspicious" :d

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    7 years ago, # ^ |
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    +28, hell yeah, How can he do that =)) Please teach me :D

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      7 years ago, # ^ |
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      that's better to avoid doing like that:)

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        7 years ago, # ^ |
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        Just kidding :D And what admin do next after this ????

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          7 years ago, # ^ |
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          +44

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            7 years ago, # ^ |
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            mnlfrnnds04 has 44 hack in his room :D and in my room overall was not 44 man

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              7 years ago, # ^ |
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              watch

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              7 years ago, # ^ |
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              How can we cheat for hacks? I don't get it... The roomates are determined randomly...

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                7 years ago, # ^ |
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                it's just luck

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                7 years ago, # ^ |
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                Maybe he has tried to do this a couple times and today he got "lucky".

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                  7 years ago, # ^ |
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                  I think he just wrote a solution that passes pretests only, then write some test cases that beat it.

                  After that, he modify the hacked solution to beat down the hack only and then invent another hack to beat down the solution again

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                  7 years ago, # ^ |
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                  You are GENIUS!!

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                  7 years ago, # ^ |
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                  Had found the same theory a little after my question, and I think you're right. But it will be detected very quickly if it is something like "if(input==hack1) then print(solutionhack1) else if (input==hack2) then print(solutionhack2) etc..." Or else, it can be too a good solution, but altered for permit hack like "if(input==hack1||input==hack2...) then print(42) else print(goodanswer)"

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                  7 years ago, # ^ |
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      7 years ago, # ^ |
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      I can't be possible...

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      7 years ago, # ^ |
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      people who are trying to explain this event, YOU'RE ALL GENIUS!

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    7 years ago, # ^ |
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    He would be first even if his A and B won't pass system tests.

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what kind of sorcery is this :) 44 hacks, same user, same country, same profile :)

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7 years ago, # |
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PRETEST 4 WAS A TRICKY ONE FOR THE PROBLEM HYDRA............... ALMOST EVERYONE HAS A WRONG ON IT........

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7 years ago, # |
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Could anyone explain me, what is the statement of the problem B? Let's assume two middle vertexes as S and T. I can't understand, could neighbours of vertex S be connected to vertex T. I thought, no. And, server problems...((

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    7 years ago, # ^ |
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    tree with h+t+2 nodes

    I think no except you don't select the neighbour nodes for both S and T

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Will this compitition be rated?The Net was error for too much time.

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    7 years ago, # ^ |
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    But they increased the time to overcome that .. So I suppose it is alright

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      7 years ago, # ^ |
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      I'm disagree.

      Imagine the following situation (it's from real contest): I opened one problem, solved it and then server gone away. I have to wait and can neither send my solution (and I lose some points), nor read the next problem (here I lose contest's time).

      Then imagine one (I know such persons too) who opens all problems in the beginning of contest. So, he have 5 additional minutes over me. Not fair, huh?

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        7 years ago, # ^ |
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        You also had the opportunity to open all 5 problems. So it is fair to everyone.

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        7 years ago, # ^ |
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        Well, I think it is reasonable precaution to open all tasks when contest starts

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        7 years ago, # ^ |
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        My situation was better: I waited for five minutes to send problem, and than waited 5 more without any other opened problem. Than I got WA. Nice:)

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        7 years ago, # ^ |
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        I'm just the first situation,and I solve the second problem but I can't submit at once,when I submit it,it's already 20 minutes later.

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        7 years ago, # ^ |
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        Imagine if you want to ask a clarification (my case). Let's hope this doesn't keep happening in future rounds.

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    7 years ago, # ^ |
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    true, it's a few unfair, e.g. bug helped me, i submitted my code in extra time.. but i think problems are similar to all of us. it can be rated i think.

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mnlfrnnds04 this person should be banned, he is first in div-2 illegally.

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    7 years ago, # ^ |
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    of course with this one too hgrsm07 :D

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      7 years ago, # ^ |
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      then I will survive unluckiness of 13 in standing :p

      Edit: as a result of omitting the cheater person, now I am ranked 12th, and consequently no person is ranked 13th! standings

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        7 years ago, # ^ |
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        And I'm 14th :) (Isn't it 13rd?)

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    7 years ago, # ^ |
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    Of course, it's not fair with the other contestants.

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      7 years ago, # ^ |
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      SusanBoyle it looks that your solutions are identical to the Manoel's. And also very similar to the rafaelclp's.

      4 solutions very similar from 3 guys doesn't seems coincidence.

      See for example: 2572280 from SusanBoyle and 2572712 from Manoel.

      Not fair, indeed.

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Rev. 2   Vote: I like it -16 Vote: I do not like it

congratulations mnlfrnnds04!! The successful of a lot of challenges is the very great achievement!!!

...Oops...? Something seems to be wrong... (o_O)

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7 years ago, # |
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The expected score for this match was 2158. :D

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7 years ago, # |
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in Problem E, In pretest, My program prints "NO" in test case 1, but my program prints right answer in custom test. Please check my program..

-------------------------------- Sorry, my program was wrong.

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I got this verdict in problem D(case 21) — "wrong output format Unexpected end of file — int32 expected". Does this mean I'm giving too much out-put? Submission link

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    7 years ago, # ^ |
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    No, it means exactly the reverse — you gave checker not enough output — it tries to read int32, but gets EOF.

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    7 years ago, # ^ |
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    It mean that you miss one (or more) integer

    UPD: I was too late(

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can tell how made problem B???

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    7 years ago, # ^ |
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    Note that there are not a lot of undoubtly lucky number upto 10^9 . So generate all of them

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    I did a backtracking solution. You try all the pairs of (x,y), after that you produce all the possible numbers with a backtracking. This gives approximately O( 10^2*(2^10-2) ).

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Thanks for the great contest... :D waiting for the the tutorials... :D

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Div1 for first time .. so happy :D

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Can anyone tell me why this brute force solution is able to pass Problem A (Div 1)? Solution I am not able to prove its worst case complexity. Perhaps, it is because of the pigeonhole principle. Is it possible that the tests were weak?

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    7 years ago, # ^ |
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    Your code is correct and runs in O(N*20) for the worst case. When inner loop breaks with (temp==cur[j]) condition, it means that, a[j] and a[i] has some bit b set in their binary representation, but none of the a[j+1],....,a[i-1] has this bit set. If we contribute (i-j) to b(or to one of the bits which has above property), we see that for each 0<=bit<=20 we will do at most O(N) operations.Therefore complexity is O(N*20).

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Was getting a TLE on Test 47 for problem B, and after the contest changing the loop from 0 -> N — 1 to N — 1 -> 0 reduced the time from hitting the TL on 2000ms to 281ms!

I still can't see any sense in making the TL that strict on the problem.

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please provide a copy of the editorial in english please.

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Rev. 2   Vote: I like it 0 Vote: I do not like it

hi, i'm confused that why the java function BigInteger.isProbablePrime always lead to Runtime Error? It's right in some OJ, but always RE in others like CF. Can you explain it? Thank you!

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    7 years ago, # ^ |
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    It has been discussed in Russian somewhere. The problem occurs because of security policies: BigInteger.isProbablePrime() uses SecureRandom which could be prohibited

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When we can have the tutorial??

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The post said that day (contest day) "Editorial will be tomorrow." actually it didn't happened. But we can't say the are saying lies. because today it says "Editorial will be tomorrow.".. so logically they can never post a editorial :D but we can hope they will. (just joking) i hope this "tomorrow" will have an upper bound. :D

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    7 years ago, # ^ |
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    It seems editorial is ready, but it still isn't available in english, but you can see it in russian.

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So how do u solve The Brand New Function

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What's the idea of div2_C?

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It would be great if we have a tutorial soon :) :). waiting for the tutorial :) :) :) thanks.

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Why my code get TLE on DIV2_D?2602812,I need your help!

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What a coincidence. All the codes of SusanBoyle and Manoel look identical.