bIeah's blog

Problem of the Year
By bIeah, history, 2 years ago, In English

Hello Codeforces,

This year certainly was one of the years of all time. With it coming closely to an end, I think it would be worth to reminisce and applaud the greatest contemporary problem setting creations. Which problem made you your year?

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2 years ago, # |
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1758D - Интервал = √Суммы was the problem that surprised me the most this year — and I still don't understand my own two-pointers solution(182519051) on it!

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    2 years ago, # ^ |
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    What were you surprised by in this problem?

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      2 years ago, # ^ |
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      The fact that A-D were all mid constructives that round

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2 years ago, # |
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1673F — Anti-Theft Road Planning was the problem that made my year.

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2 years ago, # |
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I don't have a link but:

Se da un sir de cifre separate prin operatori '*', '+', '-', '/', '^', '&', 'XOR', '!' '|'. Avand voie sa faci maxim K interschimbari intre operatori, aflati valoarea maxima a expresiei.

Marinush

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2 years ago, # |
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This one

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2 years ago, # |
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1687F - Koishi's Unconscious Permutation Certainly the most complicated g.f. tasks I have solved so far.

I also like ARC145F Modulo Sum of Increasing Sequences / 147F Again ABC String.

Sorry that I haven't solve much this year.

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2 years ago, # |
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1748D - ConstructOR

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Problem with Random Tests. randomized algorithms

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2 years ago, # |
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1634B - Fortune Telling, 1740G - Dangerous Laser Power, 1740H - MEX Tree Manipulation, 104094H - One-dimensional Game.

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2 years ago, # |
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If you asked me what would be the problem that encapsulates this years the best, I would certainly answer this one. Sadly the statement is in romanian, so the broader audience won't understand it.

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2 years ago, # |
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I think maspy's D — Simultaneous Sugoroku deserves this place. Too beautiful problem.

It somehow reminds me of the dragon curve (paper folding).

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2 years ago, # |
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DMOPC '21 Contest 9 P4 — Ace of Diamonds

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2 years ago, # |
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I always look forward to seeing the blog "favorite problems of years X" :) I had so much fun solving so many different tasks through this year!

Here are some problems which made me very happy this year:

  • E. >= K it looks complex at first and it's easy to get lost in the implementation, but with a proper insight it's surprisingly simple

  • G. Anti-Increasing Addicts this just made me laugh out loud when I got AC

  • CEOI 2022 abracadabra the main idea is very cute, I saw it one Slovak problem once and I wished to see it again. My wish came true month later :)

  • E. Colorful Operations this problem looks standard at first but it has one surprisingly very cute idea which made me smile when I figured it out.

the cute idea

I'm sure there are more problems which are worth mentioning. I'll update the list when I'll remember them :)

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2 years ago, # |
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USACO January Gold P3 — Tests for Haybales

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Disclaimer: none of these is on this list necessarily because they are particularly beautiful in some algorithmic way.

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1753C - Wish I Knew How to Sort.

This is definitely the most beautiful problem I've solved this far.

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2 years ago, # |
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2 years ago, # |
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Yet another vote here for CEOI 2022 Abracadabra.

minor problem spoiler
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AGC057 C, AGC 057 D, AGC 058 D

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Although I really loved God of War Ragnarök, it turned out Elden Ring won this year.

Thanks to all problemsetters for creating beautiful tasks in this year!

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1729E — Guess the Cycle Size

An unusual type of problem, there is no solution that is 100% correct.

Also 1729 is the Hardy-Ramanujan Number, very well known in mathematics

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2 years ago, # |
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1715F —— Crop Squares

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C1,C2. Sheikh I would appreciate this problem , I tried so many different approaches and made many submissions and every time I was amazed to what test case it failed and I learned so many things too.

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2 years ago, # |
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https://loj.ac/p/3626

You have a tree, and each point has a point weight $$$v_i$$$ . You need to find the determinant of a given matrix.

Hint
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    2 years ago, # ^ |
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    Oops!It came out in 2021's winter.But it's really a interesting problem.

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G. Kirill and Company

F — Pay or Receive

E. Black and White Tree

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1705E - Mark and Professor Koro

1715F - Crop Squares

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1771C - Hossam and Trainees made the year.

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1737D — Ela and the Wiring Wizard

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2 years ago, # |
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The best problems I've seen this year are :

1750F - Majority

Spoiler

1637G - Birthday

Spoiler

1687E - Become Big For Me

Spoiler

Funnily enough, while looking through my solves, far too many good problems were made just 2 months before 2022.

My favorite problems just before 2022

1586E - Moment of Bloom

1586F - Defender of Childhood Dreams

1586G - Omkar and Time Travel

1610F - Mashtali: a Space Oddysey

1615F - LEGOndary Grandmaster

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2 years ago, # |
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I really liked solving this problem 104067H - Расстановка тыкв. Also this C is nice also 1761C - Set Construction

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2 years ago, # |
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CF :
1646E - Power Board
1736C2 - Good Subarrays (Hard Version)
1691F - K-Set Tree
1700E - Serega the Pirate
1733E - Conveyor
1743F - Intersection and Union

Atcoder :
ABC261Ex⠀--⠀Game on Graph
ABC281G⠀--⠀Farthest City
ABC272G⠀--⠀Yet Another mod M
ABC270G⠀--⠀Sequence in mod P
ABC243G⠀--⠀Sqrt
ABC268E⠀--⠀Chinese Restaurant (Three-Star Version)
ARC150C⠀--⠀Path and Subsequence
ABC263E⠀--⠀Sugoroku 3
ABC282G -- Similar Permutation

DMOJ :
YAC3P2⠀--⠀Work Experience

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1771B - Hossam and Friends

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1773A — Amazing Trick

1624G — MinOr Tree

ABC273E — Notebook

ABC268E — Chinese Restaurant (3-Star Version)

ABC262E — Red and Blue Graph

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2 years ago, # |
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https://mirror.codeforces.com/contest/1695/problem/D2

My favorite one.

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2 years ago, # |
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There were many great problems that I solved this year. Here are some that I liked the most:

Key observation
How I did it
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2 years ago, # |
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non-mentioned but very very cool problems

1667C - Half Queen Cover

1628C - Grid Xor

1654F - Minimal String Xoration

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For me it's no doubt Fake Plastic Trees 2 from Winter Petrozavodsk Day 2. It looked like a completely unsolvable problem, so it was so satisfying to finally solve it, I felt like a genius

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Doremy's Pegging Game — The idea of the solution is really nice.

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Changed my mind, this is the greatest problem

1736B - Playing with GCD

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2 years ago, # |
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ARC 147D CF 1693C

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1726A. Mainak and Array for the wrong reasons. Common mistake would be printing the difference between the maximum and minimum element. The mistake gave an answer of "996" (72 hours a week) instead of "962" (18 hours a week). So we made the servers work an "extra 54 hours" to process the influx of incorrect solutions

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For me the greatest problems were :

1762D - GCD Queries

1733D2 - Zero-One (Hard Version)

And those problems were nice and I enjoyed solving them although they are a bit easy:

1697D - Guess The String

1772F - Copy of a Copy of a Copy

1713D - Tournament Countdown

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