antontrygubO_o's blog

By antontrygubO_o, 5 months ago, In English

As the last big contest of 2021 is over, I think it's time.

It seems that there were just more and more ad-hocs/"deeply analyze some complicated process" everywhere... But maybe you still liked something.

So, what were your favorite problems in 2021?

 
 
 
 
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5 months ago, # |
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hmm, 2021 was full of interesting tasks, so I even can't enumerate them, but these problems I remembered the most:

I hope somebody will enjoy them as well as I did.

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5 months ago, # |
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Last round's problem B :)

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Codechef: Max-Min Rotations from November Lunchtime https://www.codechef.com/LTIME102A/problems/MNMXROT

Atcoder: Set merging from AGC055 https://atcoder.jp/contests/agc055/tasks/agc055_e

Codeforces: I loved Global Round 15, especially F and G were really enjoyable.

Honorable mention from other competitions: ICPC WF problem about snowblowers. Most people will think it's garbage, but I've actually enjoyed it a lot. There are at least two different clever ways to do it that are not painful.

https://open.kattis.com/problems/snoproblem

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5 months ago, # |
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none of them are coordinated by you.

Spoiler
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5 months ago, # |
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Here is my favourite problems (July ~ Dec):

interesting problems

  • CF1622F Quadratic Set by Neon
  • CF1610F Mashtali: a Space Oddysey by AliShahali1382
  • CF1612F Armor and Weapons by BledDest
  • CF1605F PalindORme by ExplodingFreeze and antontrygubO_o
  • CF1586I Omkar and Mosaic by rabaiBomkarBittalBang
  • CF1592F2 Alice and Recoloring 2 by Bakry, Hemose and KostasKostil
  • CF1567F One-Four Overload by flamestorm
  • CF1562F Tubular Bells by Wind_Eagle
  • CF1548E Gregor and the Two Painters by Benq
  • CF1552H Guess the Perimeter by cip999 and dario2994
  • CF1553H XOR and distance by mhq
  • CF1545C AquaMoon and Permutations by AquaMoon
  • CF1545D AquaMoon and Wrong Coordinate by AquaMoon
  • CF1543E The Final Pursuit by JaySharma1048576

"trick" problems

educational problems:

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5 months ago, # |
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any problem from AtCoder Regular Round

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All the problems become my favorites which I solved in contests in one go.

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The randomized solution of 1514D

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    5 months ago, # ^ |
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    Thank you! But did you even solve or look at the problems?

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      5 months ago, # ^ |
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      Yes, But this is my alt account, Because of some reasons I commented with my alt .. :D

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4 months ago, # |
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Problem E from Bytedance-Moscow Workshops camp training contest 2. You had to write a randomised implementation of binary search, such that for each $$$i$$$, you need in expectation at most $$$log_2(n + 1) + 0.1$$$ queries to find $$$i$$$.

The problem is natural and interesting, and the intended solution is clean and beautiful. The problem might seem easy, but is in fact very hard (only 2 teams and none of the top 10 of the contest solved it!).

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4 months ago, # |
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Happy holidays Anton!

My favorite problems that you authored this year are:

Unfortunately, I don't fully understand the solutions to any of them (yet).

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4 months ago, # |
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AGC055E Set Merging by antontrygubO_o.

I am curious how can a human brain come up with such solutions ?

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My favorite problem from cf : https://oj.uz/problem/view/APIO21_roads

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My favorite problems are 1549D, 1602D and YATP

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Mine is 1593G — Changing Brackets. At first I thought it was some kinda data structure (like segment tree). But, after reading the editorial, I didn't expect that the problem just became too mind-blowing for me because of its incredible constructive solution. How interesting!

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I didn't checked out a lot of problems this year, but I really liked these two problems:

I also really liked Sorter Prodigy, but it turns out to be the best problem of 2018.

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"Хорошие раскраски 2", if you know what I am talking about

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My favorite problems in 2021:

  • Final Exam, from Petrozavodsk Winter 2021 PKU Contest
  • Rectangle Painting, from Petrozavodsk Winter 2021 NNSU Contest (XXI Open Cup GP of Nizhny Novogorod)
  • Build The String, from XXI Open Cup GP of Urals
  • Slide Circuits from Google Code Jam 2021
  • Joy with Permutations, from Petrozavodsk Summer 2021 Kyoto U Contest (KCPC 2020)
  • K-onstruction, from Petrozavodsk Summer 2021(XXII Open Cup GP of IMO)
  • Pac-Man Speedrun from RuCode 4.0 Championship
  • Interesting Numbers from AMPPZ 2021 (MW Day 1, XXII Open Cup GP of Poland)
  • Short Coding from ICPC Yokohama Regional 2020 (in 2021)
  • Squid Game from ICPC Seoul Regional 2021
  • 1%-Euclidean from ICPC Moscow Regional 2021
  • Areny from Potyczki Algorytmiczne 2021, Runda 4
  • Drzewo czerwono-czarne from Potyczki Algorytmiczne 2021, Runda 5
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    4 months ago, # ^ |
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    I'm glad to hear that, but remember that the problems from Potyczki Algorytmiczne are usually used to create Open Cup rounds, so if anybody is curious about the mentioned problems -- it's best to wait.

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https://codeforces.com/contest/1551/problem/E by MikeMirzayanov. I really liked this problem, learnt something new

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Here are some of my favorite problems in chronological order of their corresponding contests and the reasons I like them:

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4 months ago, # |
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i find this problem extremely beautiful , i remember sweet struggling for few days on it .

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I am in process of solving New Year problems and if I have to nominate one problem from these it's definitely 41. Kingdoms and Quarantine (originally from some Summer Petrozavodsk contest). It's really great