Hello! Codeforces Round 826 (Div. 3) will start at Oct/11/2022 17:35 (Moscow time). You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks.

You will be given 6-8 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them)
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of our work. Problems have been created and written by ITMO University team: MikeMirzayanov, myav, Gol_D, Aris, Gornak40, senjougaharin and Vladosiya.

We would like to thank: Mangooste, Ormlis, oversolver, Be_dos, IzhtskiyTimofey, Stefan2417, ace5, BledDest, AbsurdMan, toxabuk, Kniaz, goncharovmike, YTatarin, pashka and great_fortune for testing the contest and valuable feedback. List of testers will be updated.

Good luck!

UPD: Editorial

Hello, Codeforces!

mtw, naman1601 and I are glad to invite everyone to participate in Codeforces Round 825 (Div. 2), which will be held on Oct/10/2022 17:35 (Moscow time).

This Round will be rated for participants with rating lower than 2100.

You will be given 5 problems with one subtask and 2 hours to solve them

We would like to thank:

• Arpa for coordinating the round.
• KAN for help in preparation of the round.
• Everule for proposing a task that did not make it to the final problemset.
• BucketPotato, PurpleCrayon, the_hyp0cr1t3, welleyth, MagentaCobra, recurecurring, GoatTamer, udhavvarma03, 74TrAkToR, AwakeAnay, valeriu, TheScrasse, kal013, avi0000, Perpetually_Purple, codemastercpp, CoderAnshu, IceKnight1093, Dio707, hsekharsahoo, tibinyte, Vladithur, master._.mind, mejiamejia, zalak_b, Non-origination, SlavicG, manish.17, dedsec_29, Mo2men and nor for testing this round and providing feedback.
• MikeMirzayanov for great Codeforces and Polygon platforms.

The score distribution will be announced closer to the start of the round.

UPD1: Score distribution is 500 — 1000 — ( 1250 + 2000 ) — 2000 — 2500.

UPD2: Congratulations to the winners!

Overall:

• noimi
• LJC00118
• tute7627
• kotatsugame
• Nephren--Ruq--Insania

Rated:

• Nephren--Ruq--Insania
• dongzhuo
• Kurorz
• wildfire032
• _gxyd

UPD3: Editorial is out.

Good luck and have fun!

Hello Codeforces. Hoping you're having a wonderful day! ^_^

DYTECHLAB Cup 2022

This October, we invite you to the first ever Dytechlab Cup 2022 that will start on Oct/07/2022 17:35 (Moscow time). The problems were prepared by members of our company who share a passion for Competitive Programming. It is an open and rated round for both divisions.

The round will consist of 7 problems and will be 150 minutes long. We wish everyone good luck and have a positive delta!

Prizes

• 1st place: US$200 cash prize
• 2nd place: US$100 cash prize
• 3rd place: US$50 cash prize

Also, we understand that contestants like dope MERCHANDISE, so we are giving away lots of them!

• Top 20 will get a merchandise package which will include: a t-shirt with your Codeforces handle on it, a notebook, 2 pens, and a sports bag.
• 30 merchandise packages, each including a t-shirt & 2 pens will be randomly distributed to 30 contestants ranking 21-200.
• 100 merchandise packages, each including a sports bag & 2 pens will be randomly distributed to 100 contestants ranking 201-1500.

All packages will include stickers in it, so you can stick them to your laptop and show your friends how hardworking you've been :p

Our appreciation goes to

• MikeMirzayanov for the Codeforces and the Polygon platform.
• gop2024 for coordination of the round.
• magnified for one of the problems and your enthusiastic support in preparing the round.
• blobugh for one problem that fills in the gap to finalize the contest.
• ngfam_kongu, MofK, ladpro98 and every other Dynamic Technology Lab member who helped in coordination, was spot-on while we were working together in the office and helped me come up with ideas for problems.
• The list of testers (still updating): KAN, Elite_Vanor, HmmOrange, Kuroni, .DucAnh., LetterC67, nguyentien_zzz, VanIOImaster153, ngd.nam, nigus, hank55663, VuaVeNhi, lobotomy, kieusontungcva, ehnryx, stevenkplus, MagentaCobra, dorijanlendvaj, djq_cpp, ugly2333, gyh20, TomiokapEace, SSerxhs, jeroenodb, willy108, abc864197532, -skyline-, blobugh, ak2006, satyam343, Andreasyan, emorgan.

Wish you the best and a very positive delta in this round!

UPD: score distribution is: $$$500 - 1000 - 1500 - 2000 - 2750 - 3500 - 3750$$$.

UPD2: Scripts to generate ranks of random prize winners. Seed $$$x$$$ will be the sum of score of the top 10 participants:

./genrandom_winners x

#include "testlib.h"
#include <bits/stdc++.h>
using namespace std;

/*
*  rnd.next(4) - Random int bw 0-3
*  rnd.next(4, 100) - Random int bw 4-100
*  rnd.next(10.0) - Random real [0;10)
*  rnd.next("one|two|three") Random word out of 'one', 'two' and 'three'
*  rnd.next("[1-9][0-9]{99}") Random REGEX (100-digit number as a string)
*  rnd.wnext(4,t) wnext is a method of obtaining an uneven distribution (with a biased expectation)
*  rnd.any(container) A random element of the container container (with random access via an iterator), for example, it works for std::vector and std::string
*  shuffle
*/

int main(int argc, char* argv[])
{
  registerGen(argc, argv, 0);
  vector <int> shirt_winners = {};
  vector <int> bag_winners = {};

  for (int i = 21; i <= 200; i++) shirt_winners.push_back(i);
  for (int i = 201; i <= 1500; i++) bag_winners.push_back(i);

  shuffle(shirt_winners.begin(), shirt_winners.end());
  shuffle(bag_winners.begin(), bag_winners.end());

  // list of shirt winners
  cout << "===== Rank of SHIRT WINNERS =====\n";
  for (int i = 0; i < 30; i++) {
    cout << shirt_winners[i] << ' ';
  }
  cout << "\n";

  // list of bag winners
  cout << "===== Rank of BAG WINNERS =====\n";
  for (int i = 0; i < 100; i++) {
    cout << bag_winners[i] << ' ';
  }
  cout << "\n";
}

UPD3: Editorial.

The total score of top 10 is: $$$11460 + 9086 + 8829 + 8609 + 8380 + 8354 + 7511 + 6874 + 6775 + 6755 = 82633$$$. The list of ranks of prize winners is fixed and you can check using the published code above, using the total above as a seed. I will make a list the following days and contact the prizes winners! PLEASE NOTE that the list of real winners only finalized after the system detect & remove cheaters!

Congratulations to everyone and HAVE A GOOD WEEKEND!

UPD4: standings

Winners:

First to solve:

About Dytechlab & Job Opportunities

If you are interested in employment opportunities in Eastern Europe, Dubai, or South East Asia, please fill out the contact form below:

We are Dynamic Technology Lab, Pte Ltd. (DTL), a quantitative hedge fund engaging in global securities trading with multiple asset classes. Since our founding in 2009, from humble beginnings in a home garage, we are now a sizable, well-established financial institution with offices in Singapore, Shanghai, Beijing, and Hanoi. Our success is fueled by some of the most inquisitive minds who are relentless in their pursuit of innovation.

As a tech-focused Licensed Fund Management Company under the Monetary Authority of Singapore, DTL is dedicated to producing strong consistent returns for its investors by relying on mathematical and statistical models to drive its investment process.

Right now, we are looking for lots and lots of Engineering positions and are ready to bring opportunities to work in a quantitative trading environment for Engineers of all levels, all around the world!

Learn more about us on this blog or on our website!

Hi, Codeforces!

Three years later, first ideas of a contest turned into this complete set of problems, so I am glad to invite you to take part in Codeforces Round #824 (Div. 2), which will take place on Oct/02/2022 17:35 (Moscow time). The round will be rated for the participants with rating lower than 2100. Participants from the first division are also welcomed to take part out of competition.

You will be given 2 hours 15 minutes to solve 6 problems. All the problems were created and prepared by me.

I would also like to thank:

• KAN for awesome coordination!
• Aleks5d, arzhantsev64, ChthollyNotaSeniorious, DanWallgun, MagicalFlower, Gegege337, Imakf, LeoRiether, mejiamejia, okwedook, PO3OBAR_Bblnb, SSerxhs, TomiokapEace, triple__a, wabadabakalakaboo for testing the round and giving significant feedback.
• mejiamejia for his help with extra testing.
• MikeMirzayanov, geranazavr555, unreal.eugene, DK318, and KAN for maintaining Codeforces and Polygon platforms!

Scoring: $$$500-750-1250-1750-2250-3000$$$.

Note that some problems have similar scores. Your sense of the scoring distribution may differ, don't forget to read further problems if you get stuck.

I look forward to seeing you on the leaderboard. I hope you'll enjoy all 6 problems and wish you good luck!

UPD1: Editorial

UPD2:: Winners and First to solve

Div2

Div1 + Div2

First to solve

Hello, Codeforces Addicts!

On Sep/30/2022 17:35 (Moscow time) we will host Codeforces Global Round 22.

Codeforces Global Round 22 is the $$${\textbf{2}} \cdot {\textbf{2}} = 4$$$-th round of a 2022 series of Codeforces Global Rounds. The rounds are open and rated for everybody.

The prizes for this round:

• 30 best participants get a t-shirt.
• 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2022:

• In each round top-100 participants get points according to the table.
• The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
• The best 20 participants over all series get sweatshirts and place certificates.

Thanks to XTX, which in 2022 supported the global rounds initiative!

The problems were written and prepared by antontrygubO_o, Milesian and me.

We are extremely grateful to the following people who made this round possible:

• Aleks5d as well as KAN for great coordination.
• lucifer1004 for discussion and being the first tester as this round grows.
• 4qqqq, Akulyat, alexX512, arvindf232, BucketPotato, BurnedChicken, choutii, FairyWinx, Sugar_fan, lucifer1004, lyuankai, mejiamejia, nnv-nick, okwedook, p_b_p_b, Potassium, TomiokapEace, Um_nik, yyt16384, and zjq2863974342 for testing the round and their feedback.
• MikeMirzayanov for creating great platforms Codeforces and Polygon.

Round Information:

• Duration: 2 hours and 30 minutes
• Number of problems: $$${\textbf{2}} \cdot {\textbf{2}} \cdot {\textbf{2}} = 8$$$
• Score distribution: 500 — 1000 — 1500 — 2000 — 2500 — 2750 — 3000 — 4000

Kind Tips:

• Always get ready for interactive problems no matter whether they will exist or not, please see the guide of interactive problems if you are not familiar with it.

We are looking forward to your participation!

UPD. Editorial

Congratulations to the winners!

1. cnnfls_csy

2. ksun48

3. maroonrk

4. orzdevinwang

5. ko_osaga

6. tourist

7. jiangly

8. noimi

9. peti1234

10. Maksim1744

And for the winner of each problem:

A. tourist

B. tourist

C. wind_cross

D. tourist

E. tourist

F. 300iq

G. ksun48

H. rainboy

Hello Codeforces!

On Sep/29/2022 17:35 (Moscow time) Educational Codeforces Round 136 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

This round will be rated for the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 6 or 7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Vladimir vovuh Petrov, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Our friends at Harbour.Space also have a message for you:

Hey Codeforces!

Check out our video from our relatively new campus in Bangkok. Harbour.Space@ UTCC Bangkok is located in the heart of this cosmopolitan city where tradition and modernity merge!

We are breaking down boundaries and working together for a better, brighter, tech-driven future!

Bangkok is Southeast Asia's most exciting capital and the number one place for launching a start-up in Asia. Look at our incredible campus and hear from some of our rockstar students!

To find out more about Harbour.Space University, visit https://harbour.space/.

Also, do not forget to follow us on Instagram.

Good luck, Harbour.Space

UPD: Editorial is out

Hello, Codeforces!

We invite you to Codeforces Round 823 (Div. 2) which will be held on Sep/25/2022 17:35 (Moscow time). You will be given 2 hours to solve 6 problems.

The problems were invented and prepared by shnirelman, Lankin and me.

We would like to thank:

• isaf27 for coordinating the round.

• KAN for the help during preparation of the contest.

• kevinxiehk, 74TrAkToR, Aleks5d, valeriu, satyam343, gothic_kobra, NikitaSemenov, tibinyte for testing the round.

• MikeMirzayanov for Codeforces and Polygon.

Wish you good luck and high rating!

The scoring distribution will be announced closer to the beginning of the round.

UPD: Scoring distribution: 500 — 1000 — 1500 — 2250 — 2250 — 3000.

UPD2: Editorial: https://codeforces.com/blog/entry/107293.

UPD3: Winners.

Div1:

1. heno239
2. Um_nik
3. maspy
4. jiangly
5. ksun48

Div2:

1. billieeyelash
2. PokerCareer
3. simiao1986
4. i_will_be_less_than_blue
5. Timonnable

UPD: The round has been rescheduled to a different time due to a clash with a CodeChef contest

Hello CodeForces!

Me, AHappyPotato and __jk__ are excited to invite you to participate in Codeforces Round 822 (Div. 2). It will start at 23.09.2022 15:05 (Московское время). The round will be rated for everyone with less than 2100 rating. You have 2 hours to solve 6 problems. Please note the unusual start time.

We would like to take this opportunity to thank everyone who have contributed to our round:

• darkkcyan for his excellent coordination;
• anthony123 and jerryliuhkg for proposing tasks that did not make it to the final problemset;
• thenymphsofdelphi, kevinxiehk, xuanquang1999, vinfat, ACGN, Mike4235, brianlee.lck, JeffreyLC, prvocislo, ITO, snowysecret marvinthang, QuangBuiCPP, Rekaxem, Alan, sharkycode and OGname, for testing and providing invaluable advice;
• KAN for translating the problem statements into Russian;
• MikeMirzayanov for the marvellous CodeForces and Polygon platforms; and finally,
• You, for participating in this contest!

We look forward to seeing you on the leaderboard!

UPD: Score Distribution: 500 — 750 — 1250 — 2000 — 2250 — 3250

UPD2: Editorial

UPD3: Winners!

Div 1 + 2:

1. GOI_Official
2. Um_nik
3. tzc___________________wk
4. Second_Brave_Niuniu
5. hitonanode

Official:

1. GOI_Official
2. tzc___________________wk
3. Second_Brave_Niuniu
4. Sand_Emperor
5. steven14414