hiddentesla's blog

By hiddentesla, 21 month(s) ago, In English

Hello Codeforces Community. I would like to invite you all for ICPC Indonesia COMPFEST 12 Multi-Provincial Contest Online Mirror. I am the Person In Charge of the event.

compfestlogo

I want to thank:

The online mirror will be held on , 3 hours after the official contest starts. Teams are allowed. The duration of the contest is 5 hours. For the official contestants, please refrain from joining this mirror contest.

Our problems are relatively easier than ICPC regional contests. However, we promise an interesting and diverse problem set. I'd say the overall difficulty is slightly more challenging than div two rounds. There might be an interactive problem. So make sure to familiarize yourself

About COMPFEST: COMPFEST is an annual event hosted by the University of Indonesia. It is the largest student-run IT event in Indonesia, and Competitive Programming Contest (CPC COMPFEST) is one of the competitions hosted.

Our contest on regional finder

Note: this contest is unrated.

UPD1: Editorial and contest review will be posted in a few hours, after we finish the official contest duty.

UPD2: Editorial is available here

Congratulations to the winners!

  1. Extra Registration (LJC00118, xay5421, Sooke)

  2. jiangly

  3. Bajetii (theodor.moroianu, freak93, bicsi)

  4. 未来ガジェット研究所 (wasa855, frame233, memset0c)

  5. QAQAutoMaton

  6. wlzhouzhuan

  7. 2016wudi fan club (ChthollyNotaSeniorious, leukocyte, Cirno_9baka)

  8. wucstdio

  9. Heltion

  10. Teams Are For The Weak (IceKnight1093)

 
 
 
 
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21 month(s) ago, # |
  Vote: I like it 0 Vote: I do not like it

can I participate without team?

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21 month(s) ago, # |
  Vote: I like it -33 Vote: I do not like it

is is rated???? i want to become gray

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21 month(s) ago, # |
  Vote: I like it +1 Vote: I do not like it

How many members in a team are allowed?

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21 month(s) ago, # |
  Vote: I like it +59 Vote: I do not like it

rip im 20 years too late

Spoiler
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    21 month(s) ago, # ^ |
      Vote: I like it +32 Vote: I do not like it

    whoops! sorry about that. It's fixed now.

    (effects of writing at 2 AM)

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      21 month(s) ago, # ^ |
        Vote: I like it +44 Vote: I do not like it

      Isn't it a bit unfair to post the announcement and then delay the round by 20 years?

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        21 month(s) ago, # ^ |
          Vote: I like it -35 Vote: I do not like it

        Isn't it a bit unfair that without contributing much to the community, you are 2nd top contributor.

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          21 month(s) ago, # ^ |
            Vote: I like it +30 Vote: I do not like it

          What do you mean? This is a quality post right here

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21 month(s) ago, # |
  Vote: I like it +8 Vote: I do not like it

here link is wrong.

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21 month(s) ago, # |
  Vote: I like it +14 Vote: I do not like it

Will there be any editorial for this contest?

Thanks

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21 month(s) ago, # |
  Vote: I like it +8 Vote: I do not like it

I am eager to participate !!

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21 month(s) ago, # |
  Vote: I like it -29 Vote: I do not like it

codeforces deleted my comment!!1! this is censorforces!11!!

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21 month(s) ago, # |
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How do you participate as a team?? could anyone walk me through the process it's my first time participating as a team.

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    21 month(s) ago, # ^ |
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    go to ur profile , in tag "team" create ur team, invite ur teamates, when register choose "as a team member" instead of "as individual participant"

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21 month(s) ago, # |
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Will we be able to see the live standings?

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21 month(s) ago, # |
  Vote: I like it +9 Vote: I do not like it

th level?

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21 month(s) ago, # |
  Vote: I like it +11 Vote: I do not like it

Have a feeling that this contest would be pretty interesting!

Also great to see "There might be an interactive problem. So make sure to familiarize yourself" such notification before the contest. I was clueless when I first saw an interactive problem a couple of contests back.

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21 month(s) ago, # |
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Will problems be sorted depending on the difficulty like normal CF rounds?

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21 month(s) ago, # |
Rev. 4   Vote: I like it 0 Vote: I do not like it

.

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21 month(s) ago, # |
  Vote: I like it +11 Vote: I do not like it

How many question will be set on the dashboard?

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21 month(s) ago, # |
  Vote: I like it +8 Vote: I do not like it

Will this year's INC be running a mirror on CF as well?

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21 month(s) ago, # |
Rev. 2   Vote: I like it -43 Vote: I do not like it

Nvm it'll be great :)

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21 month(s) ago, # |
  Vote: I like it -23 Vote: I do not like it

CAN I USE C++ THIS CONTEST??

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21 month(s) ago, # |
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Are contestants allowed to copy-paste code from their library or search things on the Internet during the contest?

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21 month(s) ago, # |
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will there be any rewards for the toppers of this contest?

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21 month(s) ago, # |
  Vote: I like it -11 Vote: I do not like it

will tutorial be available after contest??

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21 month(s) ago, # |
  Vote: I like it -6 Vote: I do not like it

help me out in team registration

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21 month(s) ago, # |
  Vote: I like it +21 Vote: I do not like it

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21 month(s) ago, # |
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Nice problemset! Enjoyed a lot!

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21 month(s) ago, # |
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How to solve E :|

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    21 month(s) ago, # ^ |
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    Hints for problem E
    Code
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21 month(s) ago, # |
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Any edge cases for test case 19 in D??

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    21 month(s) ago, # ^ |
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    Its

    4 3
    1 2 4 8
    17 15 16 1
    

    You can get 7 by only exciting the last atom

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      21 month(s) ago, # ^ |
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      I think the question is problem D, not E

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        21 month(s) ago, # ^ |
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        Sorry i misread the question. In D there are no edge cases (that we intend to). Maybe check your formula

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    21 month(s) ago, # ^ |
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    I found the mistake the range of n was 2000 and coordinates was 1000 I took both array of size 1000 :(

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21 month(s) ago, # |
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We will release the editorial and contest review in a few hours. right now we are so tired from nonstop supervision of contests. Sorry about the unexpected difficulty jump :( we intended B to be a medium dynamic programming problem.

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21 month(s) ago, # |
  Vote: I like it +3 Vote: I do not like it

hiddentesla Can we participate in the contest virtually?

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    21 month(s) ago, # ^ |
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    yeah. just try it

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      21 month(s) ago, # ^ |
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      It says that I am not allowed to view the contest.

      UPD: I can register for virtual now, thanks!

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21 month(s) ago, # |
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Now contest is over,but why can't I read the problems?

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    21 month(s) ago, # ^ |
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    Sorry about that. We just updated the settings. We disallowed before just to prevent the official contestants from registering

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21 month(s) ago, # |
Rev. 2   Vote: I like it +24 Vote: I do not like it

In Problem B, I think it's not very nice to mention "every checkpoint except checkpoint 1 has exactly two routes connecting it" only in the input section , since it is quite important leading to the solution :(

BTW I've spent about an hour to write&debug my B but in vain :(

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21 month(s) ago, # |
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How to solve I?

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    21 month(s) ago, # ^ |
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    Oh, I thought the editorial wouldn't be published. I'll read it :).

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    21 month(s) ago, # ^ |
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    Arrange the nodes in dfs order so that subtrees correspond to subarrays, and then simply answer each query in O(n). Runs in 3.2s without pragmas or fast i/o, and 900ms with them: Code

    Using the ternary operator is apparently important because I TLE'd when I used an if condition instead, probably some stuff going on with branch prediction which I really don't know about.

    I'm sure this wasn't intended, but I don't know if it can be made to TLE within the limits of the problem.

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      21 month(s) ago, # ^ |
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      The intended solution uses segment tree beats. We tried our best O(NQ) solution before and our fastest only got 13s. Pretty suprised we are still far away from constant optimization. Please wait for the editorial for the detailed explanation

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        21 month(s) ago, # ^ |
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        With $$$N = 50000$$$ and 7 seconds, it's hard to imagine quadratic solutions to not pass, with some minor tricks (our solution also runs in under 1s with pragmas). Was the official complexity $$$O(Q \sqrt{Q} \cdot Beats(N))$$$?

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          21 month(s) ago, # ^ |
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          $$$ Q \sqrt{Q} log (N)$$$ was the intended complexity. Yeah we are quite suprised. One solution NQ solution even manage to pass in less than 1 second sobs

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      21 month(s) ago, # ^ |
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      Is it in time!? I was trying to make a solution better than O(NQ).

      Thank you!

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        21 month(s) ago, # ^ |
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        yeah our intended solution runs at 4.000 s. However some NQ solutions run less than 1 s.

        oof

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21 month(s) ago, # |
  Vote: I like it +18 Vote: I do not like it

Weak tests for problem G XD

My program outputs lolos for case :

7 7
.......
.#####.
.....#.
..##.#.
..#MC#.
..#..#.
.......
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    21 month(s) ago, # ^ |
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    Behind the scenes: generating test cases for problem G was so hellish, that its easier to generate testcases by hand rather than using a generator program. First 25 test cases was hand made.

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    21 month(s) ago, # ^ |
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    Bad move, now they removed the problem from your standings.

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21 month(s) ago, # |
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When or where will the editorial be published for this contest?

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21 month(s) ago, # |
  Vote: I like it +49 Vote: I do not like it

problem C

detected an integer overflow error at the 154th line of the problem setter's submission:

intmod c(int K) {
	return a(3*K/2)-b(K/2);
}

K can be up to $$${10}^9$$$ so 3*K will cause overflow

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    21 month(s) ago, # ^ |
    Rev. 2   Vote: I like it +18 Vote: I do not like it

    Yeah, all of our testers used the same formula. So sorry for this. All of the submissions for C is rejudged. Only 1 participant in contest is affected.

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21 month(s) ago, # |
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how to solve D?

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21 month(s) ago, # |
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Is there any solution?

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21 month(s) ago, # |
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Can someone help me find bug in my solution for Question D? During contest, I got wrong answer on test case 9. I tried upsolving later but couldn't find the bug.

Link to the submission : https://codeforces.com/contest/1425/submission/93937461

General Idea : So the idea is to count the total number of strategies in which a & b both occur together. Let's assume they occur in X number of different strategies. Then we can add X * (2ab) to our answer (calculating a^2 is trivial and can be handled separately). Now in order to calculate X, we can consider the bounding box for a & b and then count the number of snakes in their intersection, union, and rest and can use combinatorics to calculate the answer. Please refer the code.

Can someone please explain the bug in my code?

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    21 month(s) ago, # ^ |
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    Hi, you might want to check your logic on getIntersection. Here is a small testcase that might help:

    3 1 0
    5 6 10
    4 6 30
    3 6 20
    

    Answer should be 1400.