ko_osaga's blog

Checklist for OI problems
By ko_osaga, history, 6 years ago, In English

Update 2018.11.01: Rezwan.Arefin01 made a very cool webapp which contains identical problemset, but with more usability. Thank you very much! You can check it here.

Note: There was some updates in 2018.10.05. See here for changes!

Hello! APIO 2018 is near the end, and IOI 2018 is in this September. I hope you are preparing it well!

I'm here to present my OI problem checklist :

I used this to train myself in IOI 2015~2016, and to train Korean IOI 2017 Team (probably 2018 too). For long it was in the "beta" phase, but I think it's now good enough to share!

This problemset contains about 300 ~ 400 hard and interesting problems, with appropriate judge links given. (If there is problem in judging, maybe ojuz can help that..)

Google Docs Link

I hope this can help anyone preparing for future OIs, and a complete answer to the question "How to excel at IOI-style contests" :D

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6 years ago, # |
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Challenge: solve IOI 2003 C — Reverse for 100pts.

Greater challenge: solve everything in the Yandex IOI archive for 100pts.

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    6 years ago, # ^ |
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    This challenge is now for everyone : I added IOI 2003 ~ 2006 into the spreadsheet. Yandex provides a really decent judge, and I didn't found any reason not to do this :)

    Sorry for the confusion!

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6 years ago, # |
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Maybe add POI

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6 years ago, # |
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mostafa.saad.fci

I Think It Will help You for IOI Sheet :) :)

I will Try To Solve it After Finishing Junior Sheet

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6 years ago, # |
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Where can I find the editorial for them ?

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6 years ago, # |
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The JOISC problems (until 2016) on Atcoder only have Japanese statements. Is there anywhere where I can find the english version? The official JOI page also doesn't seem to have it.

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    6 years ago, # ^ |
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    Yes, it will be same for JOI 2013 ~ 2016. This spreadsheet was written in Korean perspective, and we have a Korean translation for those, so it was included in the problemset. (I hope translator will work well..?)

    Btw I remember that there was an English version of JOI TST in opentrains (some years, not all). I will talk with ojuz about uploading it.

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6 years ago, # |
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I hope this can help anyone preparing for future OIs, and a complete answer to the question "How to excel at IOI-style contests" :D I think the answer is still incomplete :p Your list is really great and I am very thankful but how do we approach it? I mean for a beginner, how and from where should we start it?

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    6 years ago, # ^ |
    ← Rev. 2   Vote: I like it +38 Vote: I do not like it

    "how" is easy, just click the problem, and try to solve the problem :D

    For "where", I guess you are finding easy problems. Difficulty is subjective and hard to quantize (especially in OI). But obviously past problems will be easy, and IOI problems will be hard. If you really want more information, you can google for past results / standings.

    Problems in checklist are generally hard. If you are not ready to solve challenging problems in there, I strongly recommend solving USACO problems here. After you are skilled enough (to solve most silver ~ gold problems) you can work on that spreadsheet.

    Btw, I want to share one of my favorite pics. This is from some internet lectures for Korean civil servant admission.

    "How much should we study in a day? How much problems should we memorize? How many problems should we solve?"

    Admitted ones : Try as much as they can

    Others : Ask this question to someone

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6 years ago, # |
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great for interested persons!!! thanks :D

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6 years ago, # |
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i suggest you to add OSN (Indonesia Science olympiad in informatic) too

https://training.ia-toki.org/archives/3 they have english translation for the problems

i think the problems are easier than other countries OI.

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6 years ago, # |
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BTW, what happened to khsoo01 at IOI 2017?

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6 years ago, # |
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Thanks a lot for the great list!

But what about COCI I think they're very good for training I enjoy solving them ... if you had time I think it's great to add them!

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6 years ago, # |
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Thanks. It does help a lot.

And by the way, do you have any ideas about training for a certain field (i.e. data structure, graphs, etc.) instead of combined training？

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6 years ago, # |
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Long time no see! I know it's bad to hugely change the spreadsheet, but recently POI translation went back on track, so I couldn't resist to accommodate this.

POI problems are now in the checklist. Some of them are not judgeable in szkopul.edu.pl, which I've colored black. I hope kostka could solve this issue someday. :D

There are some other changes:

  • BOI 2005 ~ 2008 problems are added in the checklist — because of the same reason IOI 2003 ~ 2006 was added.
  • Added "Selected Helpful Links" section, which is a list of sites that is worthy to keep track of.
  • Minor design changes.

Now the spreadsheet contains about 600 problems.

Have fun!

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    6 years ago, # ^ |
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    Yey, Polish problems!

    I have my own spreadsheet and I'm trying to upload problems in my free time (but I don't have a lot of it). Our translator promised that the problems from the last year will be translated in this month, so you can look forward to it!

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6 years ago, # |
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Auto comment: topic has been updated by ko_osaga (previous revision, new revision, compare).

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5 years ago, # |
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Problem Territory in JOI final 2016:

When submitting on atcoder.jp(Submission on atcoder), my code gets verdict Wrong Answer on some tests. However, it's accepted on oj.uz(Submission on oj.uz).

I also download testdata of this problem and test my code with the tests giving my code WA verdict in Costume Test of atcoder, but the output is correct(checked by output file in testdata).

Is that the defect of my code or the testset on atcoder?

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    5 years ago, # ^ |
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    Your code doesn't output newline in some case.

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      5 years ago, # ^ |
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      I also thought about this, but I had not fixed the entire output lines. Sorry. Thanks.

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