### errorgorn's blog

By errorgorn, 15 months ago,

Now that Goodbye 2022 has recently concluded (I hope you liked it). Let's share the best problems from 2022 instead of only before 3 weeks ago (I am looking at you kozliklekarsky).

Btw, I have noticed a trend in these blog posts where many problems come from the last few months of the year. So I hope that we take a good look through the contests of 2022 before posting.

Also, I think it would be a good idea to share your favourite blogs of 2022 as well in case we missed out some genius blog!

• +120

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 » 15 months ago, # |   +20 Thank you for rendering my blog useless. I thought we were friends.
•  » » 15 months ago, # ^ | ← Rev. 2 →   +230 Posting "Problem of the Year" 3 weeks before 2022 ends is stupid. Instead, you should have posted it in January 2022.
•  » » » 15 months ago, # ^ | ← Rev. 3 →   -64 Bine antontrygubO_o. 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. Posting "Spotify Wrapped" 4 weeks (PATRU!!) before 2022 ends is stupid. Instead, you should've posted it in January 2012.
•  » » » » 15 months ago, # ^ |   -23 Elementar. Rezolvarea problemei necesita cunostinte despre evaluarea unei expresii aritmetice, programare dinamica.Pentru rezolvarea problemei in cazul general vom nota cu a[1],a[2],...,a[m] operanzii expresiei si cu op[1],op[2],...,op[m − 1] operatorii expresiei, unde m = [N /2] + 1.De asemenea, notam cu d[i][j][h] valoarea maxima a expresiei, ce se obtine utilizand operanzii a[1],a[2],...,a[i], expresie in care s-au folosit j operatori diferiti fata de cei corespunzatori din expresia initiala, si h operatori de inmultire. Desigur, Valoarea lui d[i][j][h] se calculeaza dinamic (cu programari dinamice)
 » 15 months ago, # | ← Rev. 2 →   +19 tibinyte always pushes his problemsI won't this time, my favorite problem this year was: Calorifer who am I kidding, of course it's Majority!
 » 15 months ago, # |   +6
•  » » 15 months ago, # ^ |   +1 I loved this problem too
 » 15 months ago, # | ← Rev. 2 →   -30 You know what? Let me just write a blog about calculating the diameter of a polygon using two pointers on the upper and lower hull, and point that blog as my favorite. THIS IS GONNA BE EPICUPD: Yes I did
•  » » 15 months ago, # ^ |   0 Brother, errorgorn did nothing wrong, why are you so malicious.
•  » » 15 months ago, # ^ |   +8 Are you sure that's correct? I think rotating calipers is cleaner.
•  » » » 15 months ago, # ^ | ← Rev. 2 →   -15 I know rotating calipers is one famous way to do it, but trust me, my algorithm is correct (tested with Robert Hood™), and I have proof that the diameter cannot be on the same side of the hull (excluding leftmost/rightmost points). I like the method because I am too stupid to understand Graham scan or Rotating calipers. (Yes, I would have used them if I understood them well enough) I am not really sure about how epic it is though
 » 15 months ago, # |   +34 Not sure about problems, but I enjoyed reading this blog, even though a lot of it is well-known. It was nice seeing someone finally compile scattered information about hashing into one place. SpoilerI was planning on writing a blog along similar lines (i.e., compiling some obscure but useful stuff), but in the end, I couldn't find a topic which doesn't have a good resource already.If you want to see a blog on some idea, please reply with a suggestion about that idea. Perhaps I could try writing something if I get the time (and the motivation of course).
 » 15 months ago, # |   +44 1733C - Parity Shuffle Sorting, 1733E - Conveyor <- The author is me, but I thought it is great problem XD.
•  » » 15 months ago, # ^ |   +102 The author is me, but I thought it is great problem XD.
 » 15 months ago, # |   +7 1758D - Range = √Sum This problem.
 » 15 months ago, # |   0 This problem was a great one.
 » 15 months ago, # | ← Rev. 4 →   +69 Here are some problems I possibly liked/found interesting this year: Only problems from the contests I participated/upsolved soon/tested are included in the selection. I didn't participate a lot this year and I believe that lots of good problems aren't here just because of this (or because I accidentally forgot them).
 » 15 months ago, # |   +84 Spotify, Reddit, Steam and maybe some other things post their yearly summaries in early December too. I don't get it. kozliklekarsky was just following their trend
 » 15 months ago, # |   +40
•  » » 15 months ago, # ^ |   +25 After having some time to understand the editorial for Good Bye 2022, I would add 1770H - Koxia, Mahiru and Winter Festival to the list. My favorite contest of the year was probably Codeforces Round 808 (Div. 1) but Good Bye 2022: 2023 is NEAR would be quite close to the top. Thanks to all the authors and coordinators!
 » 15 months ago, # | ← Rev. 2 →   +74 Here's a list of my favourite tasks this year. Thanks to the authors! Strange Instructions from Hello 2022. Flights from JOI Spring Camp 2022. A=B from Moscow Pre-Finals Workshops 2022 Contest 5. (XXII Open Cup, Grand Prix of Yuquan) Longest Increasing Subsequence from Bytedance-Moscow Workshops 2022 Final Contest. (XXII Open Cup, Grand Prix of Bytedance) Good Game from Canadian Computing Olympiad 2022. Flights to the road from Baltic OI 2022. Triangles from Google Code Jam 2022 World Finals Imbalance from XXV открытый Чемпионат Урала по спортивному программированию. (XXII Open Cup, Grand Prix of Siberia) 机器人表演 from UOJ NOI Round #6 Day1. Partial Virtual Trees from Codeforces Round #808 (Div. 1). 澡堂 from IOI 2023 China Team Training (CTT 2022). Happy Game from Xmas Contest 2022.
 » 15 months ago, # |   -21 I don't know if it's only me but I really enjoy reading blogs about cheaters a lot.
•  » » 15 months ago, # ^ |   +19 Because you want to know how to write a blog to say you're not a cheater when you've got skipped for the third time? (He's a cheater himself and he's been caught twice).
•  » » » 15 months ago, # ^ |   -34 Well, I had cheated back then (and this is almost 9 months ago when I started CP) because I was very focused on my rating and was afraid of getting negative delta. Later on, I was overwhelmed with guilt and decided never to do it again.
 » 15 months ago, # |   +79 If you were aware of that previous blog, you could have just commented there.We will soon have "what is your favorite blog about your favorite problems in 2022"?
 » 15 months ago, # | ← Rev. 2 →   0 Problem, Nice problem, also Problem2
 » 15 months ago, # |   -8 My favourite blog is Bakry's blog https://codeforces.com/blog/entry/110245 it is really inspiring.My 2023 goals are to reach CM hopefully and to do well in my country's National Olympiad.Happy New Year Every One, Hope you all achieve your Goals.
•  » » 15 months ago, # ^ | ← Rev. 2 →   -7
 » 15 months ago, # |   +46 some of my favorite tasks in 2022:From Atcoder: From Codeforces: Others:
 » 15 months ago, # | ← Rev. 2 →   +5 obviously goodbye 2022 C
 » 15 months ago, # | ← Rev. 6 →   +19 Did not do problems on other OJs as much so this list only mainly contains problems from CF commentsThis problem is a horrible div 2B but its the greatest anti-problem this year. Definitely one of the most memorable div 2Bs of all time. commentsOriginal constraints are not that interesting. The thing I like about this problem is that we can prove that the answer obeys a linear recurrence of length $K$ which can be calculated in $O(2^K)$ time. commentsIdea is really nice but the implementation is not fun. commentsAuthors proposed this as d1A Also some problems from atcoder that I recall (wasn't really active on atcoder though) Others: commentsThis is definitely bias from this being such a recent contest but I can't believe the 3-5th place (including me) choked on such a simple (in hindsight) greedy observation commentsflamestorm proposed this for a contest but a tester found out it had appeared earlier in 2022 so we could not use it. Very sad, was my favourite problem of the contest.
 » 15 months ago, # |   +31 Unfortunately, I don't have any favorite problems in 2022. APIO2022B, AGC059C, IOI2022F deserve some honorable mentions, I think.
 » 15 months ago, # | ← Rev. 3 →   +18 I think these Codeforces problems were good:1634F - Fibonacci Additions1637G - Birthday1682E - Unordered Swaps1698F - Equal Reversal1707F - Bugaboo1737D - Ela and the Wiring Wizard1774G - Segment Covering1770F - Koxia and SequenceHonorable mention: 1685E - The Ultimate LIS Problem