Good Day Codeforces!

Me and Tsovak are happy to invite you to take part in Codeforces Round 972 (Div. 2), which starts on Sep/14/2024 17:35 (Moscow time). You will be given 5 problems and 2 hours to solve them. Two problems are divided into two subtasks.

The round will be rated for all participants with a rating lower than 2100.

The problems were authored by me with Tsovak's help to solve and alter them.

We would like to thank:

• TheScrasse, Kaey for wonderful double coordination and chess skills.

• Alexdat2000 for Russian translation.

• turmax, BurnedChicken for nutella testing.

• physics0523, Andreasyan, Arayi, zidder for red testing.

• FelixArg, _LeMur_, _RedWine_, Error_Yuan for orange testing.

• c2zi6, GaGeV, alex_2008, CyberCow, kHarsh3715 for purple testing.

• chromate00, Mher777, dilanyan, Zhora_.004, SashaT9, vikram108, a-c, Doctor_Strange_ for blue testing.

• _PhantomDeluxe_, Arpi2007, tigranmatsak_9, Gurgen_Melikyan for cyan testing.

• ishaandas1, Sonya_2009 for green testing.

• gvardanyan062, Binary_Thinker for grey testing.

• tibinyte for colorblind testing.

• MikeMirzayanov for the great platforms.

• Vinton Cerf, and Robert Kahn for inventing the internet.

• You for participating!

Score Distribution: 750 — (500 — 500) — 1500 — 2250 — (1500 — 2000)

UPD1: The Editorial is out.

UPD2: Congrats to the winners!

Div.2:

1. SSKMF

2. kkkksc03

3. achen.80

4. cqbztl

5. yanold

Div.1 + Div.2:

1. jiangly

2. aryanc403

3. Ormlis

4. maspy

5. kotatsugame

On the left, you see Tsovak with TheScrasse at IOI 2024.

On the right, you see me with Tsovak at IOI 2024 (I Owe Ice Cream 2024).

One of my friends (GaGeV) was flying to IOI. I have a hobby of flying in flight simulators, so I told him I know one of the flight attendants named Jessica. I told him to ask her, and she'll upgrade him to business. I didn't expect that he'd actually do it and send me this video, though. Let's hope that on the returning flight Jessica will admit that it's her working on Qatar Airways.

In the recent div 2 contest, I finally became expert, and since a lot of people ask how to improve, I decided to share my own experience of competitive programming. It all started 1 and a half years ago, when I decided to go to the programming club of my school. Of course, it all started by a very tough problem (given a, b. Print a + b), but I managed to pull it off. And after solving a bunch of classic and simple problems like that, it was a big improvement, of course, considering that I knew nothing. But at some point, I started noting that I'm not really improving anymore (it was around the time when I started codeforces and didn't reach pupil yet). That's when I realized that it's great to have someone teaching you, but you need to work alone to keep improving.

I started solving codeforces problems more (Let's all take a minute of silence for my 1st amazing submission — 128902691). It all went pretty smooth until I reached pupil. I started learning more advanced algorithms such as binary search, prefix-sum, dfs, bfs, and a bit of dp. Even after that, I still didn't manage to become a specialist, and the way I became specialist was by starting to do more paper work and believe in myself. Most of the time, I'd say C is definitely hard for me and not even take half of the time in the contest.

Specialist was where I've been stuck for many months. I started learning segment tree, solving a bunch of high rated Segment tree problems on codeforces. I also learned 2d prefix sum, improved my dp knowledge, and of course solved many problems in these topics. I felt massive improvement in olympiads after doing those stuff, but I was really annoyed that I wasn't improving on codeforces. I decided to not give up and started solving div 2 D problems. I was rarely solving it during a contest, but many times I was managing to upsolve the div 2 D on my own (Don't be afraid of looking at the editorial, if you're not able to solve it). A final touch was giving some virtual contests and upsolving them. After that, I slowly started to increase from low 1400 to low 1600.

At the end of the day, I encourage you to follow the advice of smarter people, and I'll probably become specialist again in the next contest. :)