intrusiv's blog

Problem of the Year 2023
By intrusiv, history, 11 months ago, In English

Hi Codeforces,

Time goes by, and so should we. And it seems that the time has come for this year. So, it's a great time to reflect on and appreciate the standout problem sets that made this year memorable. What specific problem stands out to you as the highlight of your year?

PS: For the problems included in some of the most upvoted comments, I think I will host a poll to truly get the best problem of the year (so problems should be from a contest pertaining to this year). Applications (meaning comments taken in consideration) for this will naturally close at the end of the year after we've had time to see all of them.

  • Vote: I like it
  • +76
  • Vote: I do not like it

»
11 months ago, # |
  Vote: I like it -50 Vote: I do not like it

For me it is Milica And String

→ Reply
  • »
    »
    11 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Note that "1 A" and "3 A" are also correct one-operation solutions.

    This problem statement update makes the problem 100 times easier.

    → Reply
»
11 months ago, # |
  Vote: I like it -89 Vote: I do not like it

Watermelon

→ Reply
»
11 months ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

I've mentioned this before, but CF round 887 contains some of my favorite problems of the year. ABC are all great, B in particular is one of the best constructives I've seen (at least for problems of that level). This round also holds a special place in my heart, as my first ever div1 contest ;)

→ Reply
»
11 months ago, # |
  Vote: I like it 0 Vote: I do not like it

1882D - XOR на дереве

→ Reply
»
11 months ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

1889B - План подключения от Дореми Interestingly enough when I solved it I didn't really feel anything but only when I was discussing it with my friend this problem somehow touched my heart

→ Reply
»
11 months ago, # |
  Vote: I like it -41 Vote: I do not like it

https://codeforces.net/blog/entry/122360 Can anyone help me to solve the above question

→ Reply
»
11 months ago, # |
  Vote: I like it +22 Vote: I do not like it

Mine is definitely to become max since …

Spoiler
→ Reply
»
11 months ago, # |
  Vote: I like it +30 Vote: I do not like it

In order of difficulty:

Comments
→ Reply
  • »
    »
    11 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    in Game of Stacks , idea is to remove the cycles since their removal will not affect the result.

    → Reply
    • »
      »
      »
      11 months ago, # ^ |
        Vote: I like it +5 Vote: I do not like it

      I mean, the idea is quite intuitive after you come up with it, but it's hard to believe something so simple just works.

      → Reply
      • »
        »
        »
        »
        11 months ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Agreed , I also find the idea quite neat and beatiful. I think it is a good candidate for the problem of the year.

        → Reply
»
11 months ago, # |
  Vote: I like it +45 Vote: I do not like it

My most favourite is for sure 1844G - Дерево с весами. The problem itself is natural, and the solution is cute!

→ Reply
»
11 months ago, # |
  Vote: I like it +25 Vote: I do not like it

For me it is Tourism from JOI Spring Camp :3

→ Reply
»
11 months ago, # |
← Rev. 3   Vote: I like it +2 Vote: I do not like it

D2. Prefix-Suffix Palindrome (Hard version)

Iva & Pav

Data Structures Fan

Sum in the tree

→ Reply
»
11 months ago, # |
← Rev. 2   Vote: I like it +26 Vote: I do not like it

Serval and Brain Power by Serval (February)

M-tree by RDDCCD (March)

Tenzing and Tree by ??? (June)

Imbalanced Arrays by synths (July)

Candy Party (Easy) by Error_Yuan (September)

Turtle and GCD by skye__ (October)

Bonus! Aranara Game (easy) by oursaco (March)

Spoilers!!!

As always, thanks to all problemsetters who wrote problems this year :). Thank you for writing problems!

→ Reply
»
11 months ago, # |
  Vote: I like it +8 Vote: I do not like it

https://codeforces.net/problemset/problem/1863/H

Loved the Pinley round in general, especially Goldberg Machine 3. Thanks Endagorion!

→ Reply
»
11 months ago, # |
  Vote: I like it 0 Vote: I do not like it

This is a good shortest path problem: 1860E - Редактор с быстрым перемещением

→ Reply
»
11 months ago, # |
  Vote: I like it 0 Vote: I do not like it

As a beginner , this problem 1872E - Фанат структур данных was one of the best competitive programming problems I've ever seen, its simple idea really blowing my mind

→ Reply
»
11 months ago, # |
  Vote: I like it 0 Vote: I do not like it
→ Reply
»
11 months ago, # |
  Vote: I like it -8 Vote: I do not like it
  1. Iva & Pav
  2. Reverse Madness
  3. Small GCD
→ Reply
»
11 months ago, # |
  Vote: I like it +3 Vote: I do not like it

koxia and number theory

→ Reply
»
11 months ago, # |
← Rev. 3   Vote: I like it -10 Vote: I do not like it

For me its of course

https://codeforces.net/contest/1875/problem/E (Jellyfish and Math)

Just look at the difference between number of people who solved D and E

What I like about this problem is the reduction to shortest path in graph and the construction was also pretty ingenious among other things, definitely the best problem I have seen so far

PS : Also this round was also my first CF round

→ Reply
»
11 months ago, # |
  Vote: I like it -24 Vote: I do not like it

Swap and Reverse

→ Reply
»
11 months ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

1804F — Approximate Diameter

1835C — Twin Clusters

1863G — Swaps

1876E — Ball-Stackable

AGC064D — Red and Blue Chips

comment
→ Reply
»
11 months ago, # |
  Vote: I like it +6 Vote: I do not like it

Here are some problems I remember being very nice imo (in no particular order):

→ Reply
»
11 months ago, # |
  Vote: I like it +1 Vote: I do not like it

1860D - Сбалансированная строка , this is the problem that took me to the candidate master !!

→ Reply
»
11 months ago, # |
  Vote: I like it +5 Vote: I do not like it

1830E — Bully Sort

(totally unbiased opinion :clown:)

→ Reply
»
11 months ago, # |
← Rev. 3   Vote: I like it +6 Vote: I do not like it

Probably sorted by difficulty:

Spoiler
→ Reply
  • »
    »
    11 months ago, # ^ |
      Vote: I like it +5 Vote: I do not like it
    Hint for subtask 7 of the last problem
    → Reply
»
11 months ago, # |
  Vote: I like it +10 Vote: I do not like it

Personal opinion of the candidates of best problems that I have viewed or done: (in no particular order)

1834E - MEX НОК

1854D - Майкл и отель

1789F - Serval и Brain Power

1889D - Игра со стеками

1863G - Swaps

1844G - Дерево с весами

1844F2 - Перестановка минимальной стоимости (сложная версия)

→ Reply
»
11 months ago, # |
  Vote: I like it 0 Vote: I do not like it
→ Reply
»
11 months ago, # |
  Vote: I like it 0 Vote: I do not like it

problems I found interesting and/or learned a lot from

1864D — Matrix Cascade

1864E — Guess Game

1854A2 — Dual (Hard Version)

1848F — Vika and Wiki

1844E — Great Grids

1817D — Toy Machine

1794D — Counting Factorizations

1859E — Maximum Monogonosity

1852C — Ina of the Mountain

→ Reply
»
11 months ago, # |
← Rev. 5   Vote: I like it 0 Vote: I do not like it

My Favourite Problems are:

1843E-Tracking Segments

1883C-Raspberries

1899E-Queue Sort

1903C-Theofanis' Nightmare

1878E-Iva&Pav

1850F-We were both children

1907E-Good Triples

→ Reply
»
11 months ago, # |
← Rev. 2   Vote: I like it +2 Vote: I do not like it
→ Reply