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Arpa's blog

Topcoder SRM 787
By Arpa, history, 4 years ago, In English

Hello, Codeforces community!

I am very proud to announce SRM 787 is underway, authored by me. The contest will start today at 16:00 UTC.

It is my third experience in holding a contest at Topcoder. Holding contests on Topcoder is always memorable, having misof as contest coordinator and hmehta as a kind helper, it can't be nice more. Although struggling with Java and MPSQAS is not easy, being with a kind and professional team makes it sweet. So thank you Misof and Harshit! Also, Misof tested the contest.

Problem stories are all about my honorable mighty teacher, Abolfazl Asadi, who is currently doing great in teaching students and preparing them for INOI (Iran National Olympiad of Informatics). You will know him in problem statements as "Aqa Asadi". "Aqa" means "Sir" in Persian.

Abolfazl Asadi

I can't skip thanking my dear friend Javad javaD Karimi, who proposed the idea of Div. 1 Easy.

P. S. Please note that the coding phase will begin at 16:05 UTC but the registration will still close at 15:55 UTC.

Good luck to everyone!

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Comments Comments (53)
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4 years ago, # |
  Vote: I like it +38 Vote: I do not like it

It has been a year now since I registered on topcoder and still I haven't figured out how to compete there?Please provide the contest link.....so that I can participate...

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

    Currently, there are two ways that you can compete in Topcoder contests (SRMs): the Web Arena and the Applet Arena. The Applet Arena has been around for 15+ years, has richer functionality, and provides a better overall experience, but it requires some extra setup.

    • WEB ARENA(Beta) The Web Arena requires no special setup since it is just a regular web page. However, its functionality is limited as it doesn't support any editor plugins and is still in beta mode at the time of this writing.

    • JAVA APPLET ARENA(Recommended) Topcoder Java Applet is the older way of competing. Most experienced competitors use the Applet Arena and it is also used at the Topcoder Open Onsite Finals. It has several plugins you can use to enhance your experience.

    To launch the Applet Arena, you need to make sure you have the Java runtime environment (JRE) installed. You can get that here. Make sure you add the list below in the exception list of your Java Control Panel.

    More details here: Setting up Topcoder Java Applet

    Once you are set — take a look at this detailed How-To-Compete Guide

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

      Was the topcoder applet designed to disable you to copy paste some code or is it just me in my macbook?

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

        You should use Ctrl+V in macbook instead of CMD+V.

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

        Use control + C and control + V for the same instead of command + C and command + V

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

          Oh! Was trying that but some weird characters pop-out, maybe i mispressed the button.

          Thanks!

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

Is it for Div 1 only?

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

    Every SRM (Single Round Match) has two different problem sets for Div I and Div II competitors, with each having three problems. (sometimes one problem is shared between the two sets too)

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

Gentle Reminder: The match begins in 1 hour and 15 mins

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4 years ago, # |
  Vote: I like it +94 Vote: I do not like it

TERRIBLE samples on Div 1 1000!!!

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    4 years ago, # ^ |
      Vote: I like it +36 Vote: I do not like it

    +1000

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

    Even from an objective perspective, they must include samples with pseudo-random generation...

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4 years ago, # |
  Vote: I like it +44 Vote: I do not like it

I thought there was already enough negative feedback for problems like A, C today. Apparently I was wrong :)

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

    No, you are just fast enough to post a comment here. I have the same feeling for those two problems.

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

      I meant enough feedback after past rounds with problems like that :D

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

    Why don't you like the 250?

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

      It's a nice problem, but not for topcoder.

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

        I think 250 is the only nice problem for topcoder in this round (except for the input format) unless one solves it technically.

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

        idk, I'd say that there is one nice observation you need to make, and implementation is very concise, so it's fairly good. Except for the input generation thing, but that's just topcoders' legacy.

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

        What's different about it compared to other Div1 Easy problems? At least this is somewhat nicer, because there is no corner case where the general approach doesn't work (I am surprised how quite a few people failed system tests on this).

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

        Can you explain what you mean by "problems like A, C today" (I didn't do the round, but I wonder if it's possible to state in a sentence so I understand). Thanks!

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

    kabuszki, thanks for your feedback. Can you please describe your sense more? i. e. why you didn't like A, c?

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

250: https://open.kattis.com/contests/ncna18open/problems/lipschitzconstant , though I would assume it's not the first time this idea was used.

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

I am little bit surprised with so small AC rate at D1 Easy. Task was pretty obvious to me.

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4 years ago, # |
  Vote: I like it +64 Vote: I do not like it

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

    I was thinking about this comment during participation but exactly in the opposite way, 250 seemed really hard to me today, I got some weird shit in $$$O(n \log^2 n)$$$ xD (and got hacked on TLE??? seems unexpected to me, sadpepe)

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      4 years ago, # ^ |
        Vote: I like it +33 Vote: I do not like it

      Nice thing about writing contests on Java — you don't even think $$$O(n \log^2 n)$$$ could pass with $$$n$$$ = 500k :)

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4 years ago, # |
  Vote: I like it +139 Vote: I do not like it

I'm seriously considering skipping Topcoder until test generation is got rid of. I know it's there because of ancient backend and arena, and probably will never be fixed, but I'm so done with this shit.

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

    After previous round and 3/3 with generators, this was an amazing experience to me.

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    4 years ago, # ^ |
      Vote: I like it +118 Vote: I do not like it

    Even if they will change the test generation, I don't think that the current Topcoder worth participation.

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

    I don't really do TC, but what are the issues with the test generation? (I think it's super annoying, but is there another issue with it?)

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      4 years ago, # ^ |
        Vote: I like it +31 Vote: I do not like it

      No pretests. You may get fked due to a single typo in test case generation. People hate platform most when they are fked due to test case generation instead of an algorithm. click

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

        Regardless of whether they fix the test generation issue or not, pretests should be there. Minor mistakes happen in algorithm as well, even to the best (look at SRM 785 Div1 Hard).

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

Hey everyone, today was my first SRM and after reading some of the comment threads I have a few questions on how tests work.

Are there pretests? Or is your code judged only on sample cases before system testing.

When solving problems during practice, is your code only run on sample cases, or on the entire set of cases? I was doing several Div. 1 Easys for practice and never once did I get a "submission unsuccessful"

Thanks for a great first Div 2 round, did not expect to get 2nd.

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

    No, there are no pretests. Only sample tests, and then system tests. It is also not compulsory to pass samples. You can submit if your code compiles :(

    So during practice, you must run system tests yourself. In the web arena, the 'Run System Tests' option is right beside the options to Compile, Test during practice. In the applet, I think it's in the Practice Room Options menu.

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4 years ago, # |
  Vote: I like it +26 Vote: I do not like it

What's up with the hate on this contest? Problems were fine to me. Of course test generation and terrible samples are always a bit pain, but for one I have no idea about why "A is a good problem but not for topcoder" (summon kabuszki)

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

    We are the customers and we just express our opinions. I was also thinking that there is no need to hate this contest but if others have a different opinion, they are free to express it. In the end, the goal is to improve the overall quality and experience for everyone.

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

      What a generic void comment xd. First thing — "customers" — really? Second thing, of course I am aware everybody has its own opinion, so I just wanted to ask for some more justification from the ones that complained. "In the end, the goal is to improve the overall quality and experience for everyone." — you can't really do much with the feedback "Easy is a bad problem".

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

        It doesn't matter, the contribution is up!

        You could always get something out of the comments — even if they are just "I don't like it". In most cases, it just means that the problems were too hard. In this particular case, there is also an input generation issue. I also noticed weak pretests complaints.

        I think that this is something that author can think of for the next time.

        As regards customers — yes we are. the author is paid by TC, to prepare the problems for us to solve. Any business model they use, it won't work without us.

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

    I am no masochist, so if I wanted to solve regular problems, I wouldn't do that on TopCoder platform.

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

    Easy was nice, but medium and hard were not to my taste. Medium is generic subsegment dp. Hard is really boring.

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

      Um_nik, I really appropriate your feedback, but can you describe more why Hard was boring?

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

        You look at the statement and say "ok, we have to find bridges, calculate damage for each bridge, build a tree on them, then determine the minimal damage assuming we can save one path". All that happens faster than reading statement (it's kinda hard to read, sorry) because all of these steps were already presented in different problems before, even in the exact same setting (i.e. you can add one more edge to minimize damage). The last step is kinda new (at least for me), but it is also obvious that we should sort the bridges and find the first one that is not on the path with all the previous, which is again well known.

        And then you have to write boring tree stuff. idea/implementation ratio tends to 0.

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

          Dear Um_nik, it was not needed to create the tree. Implementation is easier than you think. Can you please take a look at my solution?

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

            That's not easier, that's just different.

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

Would it be possible to provide a language-specific input generation functions in the statement? That may make life easier and prevent future complaints.

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

    I definitely agree, exactly my thoughts. Provide copy-pasteable language-specific generators and people will be much happier.

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

      No thanks, Ctrl-C Cmd-V won't make me happy.

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

        But "ctrl-c + ctrl-v" is still much much more pleasant than "ctrl-c + ctrl-v + adjusting code". I didn't say you will become happy, I said you will become happier :) (or at least I will)

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

Is the round rated? My rating is yet to be updated.

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