Hello, Codeforces!

I, ChurakovaAlexandra, and medvezhonokok are students of ITMO, and since this August, we started our internship at Codeforces. We are delighted that now we have the opportunity not only to write academic code but to do something that competitive programming enthusiasts from all over the world use.

Currently, we are working on minor improvements to Polygon — a system for preparing problems. Later, as we gain more experience and delve into the technologies, we will also start working on Codeforces.

A big thank you to our mentors geranazavr555 and MikeMirzayanov, who are always there to help and support.

Here's a list of the main improvements to Polygon that we've made (sometimes with significant help from our mentors) over these two months.

Hello! Codeforces Round 903 (Div. 3) will start at Oct/12/2023 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 7 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.

Problems have been created and written by our team: myav, Gornak40, senjougaharin and Vladosiya.

We would like to thank:

1. MikeMirzayanov for Polygon and Codeforces platforms.

2. SomethingNew, rniya, zwezdinv for red testing.

3. makrav, snowysecret, AlexanderL, KseniaShk, pavlekn for yellow testing.

4. gigabuffoon, EgorUlin, KerakTelor, Pa_sha, I_love_geom, petyb, MinaRagy06, toniskrijelj, FynjyBath for purple testing.

5. Abo_Samrah, dan_dolmatov, pedrosorio, ezdp, azureglow, Chrisedyong, Apachee, arseny2606 for blue testing.

6. t0rtik, Sergey140146659, hader239, Modern for cyan testing.

7. mkshh, petertromso for green testing.

Good luck!

UPD: Editorial

Hello Codeforces!

On Oct/09/2023 17:35 (Moscow time) Educational Codeforces Round 156 (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, Ivan BledDest Androsov, Maksim Neon Mescheryakov, Roman Roms Glazov, Alex fcspartakm Frolov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Please note that the problems of this round partially intersect with the problems of the Qualification stage of the Southern and Volga Russian Regional Contest. If you took part in the qualification, please refrain from participating in the round.

Good luck to all the participants!

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

Scholarships for Master's students in Computer Science and Data Science are available in Harbour.Space University Barcelona campus!

Scholarship Summary:

• Fully funded scholarship (29.900 €/year) to study a Master’s degree in Data Science or Computer Science for two years
• Successful applicants will become part of the University’s “Talent pool” and will be shown to the sponsoring companies. In case the candidate is picked for the Work&Study Program from our industry partner, the student starts an internship with a commitment to study 3 hours/day and work for 4 hour/day

Please note preselected candidates will be requested to pay a non-refundable application fee of 85€ to study at Harbour.Space University.

Candidate’s commitment:

You will complete 15 modules (each three weeks long) in one year. The daily class workload is 3 hours, plus homework to complete in your own time.

Candidate’s requirements:

• Bachelor's degree in the field of Mathematics, Statistics, Data Science, Computer Science or similar
• English proficiency
• Advanced knowledge and experience in Python, SQL, Spark/Scala, and bash
• Experienced use of Big Data technologies: Spark, HDFS, Kafka, etc.
• Hands-on experience with Data Science techniques: feature engineering,
• Strong ML knowledge
• Strong Software Engineering Background
• Problem-solving aptitude

Note: These scholarships are only available for qualified applicants with a bachelor’s degree.

UPD: Editorial is out

Sugeng enjing, Codeforces! 🥰🥰🥰🥰

COMPFEST 15 is happy to invite you to participate in Codeforces Round 902 (Div. 1, based on COMPFEST 15 - Final Round) and Codeforces Round 902 (Div. 2, based on COMPFEST 15 - Final Round) on Oct/08/2023 12:05 (Moscow time). Both rounds will be rated. You will be given 2 hours and 30 minutes to solve 7 problems.

Note the unusual time of the round.

The problems are written by ArvinCiu, Pyqe, and nandonathaniel.

We would like to thank:

• KAN for helping to host the round;
• errorgorn and ScarletS for the based coordination;
• gansixeneh and nandonathaniel for helping with the problem preparation;
• ArvinCiu, CyberSleeper, and Edbert.H for providing alternate solutions in the early stages;
• Alexdat2000 for writing the Russian translations;
• Aaeria, AMnu, Berted, BucketPotato, buffering, Drew_, dorijanlendvaj, eggag32, Elben85, emorgan, faustaadp, ffao, fishy15, flamestorm, gamegame, hocky, Insta-x, jdurie, joelgun14, KerakTelor, Marky, Murinh0, nvmdava, yz_, Owmicron, prvocislo, PurpleCrayon, rama_pang, TakeMe, sahil_k, user202729_, Vladithur, WHCPP, and ZeroScar for testing the contest and providing us very useful feedback;
• Universitas Indonesia, all the local committees, administrators, and managers of the whole COMPFEST event;
• MikeMirzayanov for the amazing Codeforces and Polygon platform!

COMPFEST itself is an annual event hosted by Universitas Indonesia. It is the largest student-run IT event in Indonesia and competitive programming contest is one of the competitions hosted.

We hope you will enjoy and have fun in the contest. Muga-muga beja lan isa entuk biji apik!! 💪💪🔥🔥

UPD: Scoring distribution

• Div. 1: 500 — 1000 — 1250 — 1750 — 2250 — 2750 — 3250
• Div. 2: 500 — 1000 — 1500 — 2000 — 2500 — 2750 — 3000

UPD2: Contest is over!

Congratulations to our winners!

Congratulations for our first solvers:

We will try to post the editorials as soon as possible. Please stay tuned!

UPD3: Editorial

On behalf of the COMPFEST committees, we are glad that our Codeforces Round ran quite smoothly and we hope that you all enjoyed our problems. See you next year! 😍😍

Hello, Codeforces!

We've compiled a list of command lines that Codeforces uses to compile and run solutions in various languages and compilers.

It is up-to-date as of today (2023-10-06), and we will make efforts to keep it current in the future, but this is not guaranteed.

Hello, Codeforces!

I'm pleased to invite you to Codeforces Round 901 (Div. 1) and Codeforces Round 901 (Div. 2). It starts on Sep/30/2023 17:35 (Moscow time). It also means, the National Day of China arrives during the round. Wish you a nice vacation! 🎉🎉🎉

For both divisions, you will have 3 hours to solve 7 problems.

I would like to thank:

• errorgorn for his wonderful coordination.

• Alexdat2000 for Russian translation and Vladosiya for helping us with Russian clarifications.

• Atomic-Jellyfish for providing all the problems and "a few" rejected problems.

• PersistentLife and SanweiTreap for helping me prepare the problems.

• Um_nik, wangziji, Sugar_fan, Kevin114514 and MagicalFlower for Legendary Grandmaster Testing.

• sjcsjcsjc, He_Ren, GaryZ005, platelet, njwrz, thenymphsofdelphi, DerekFeng, Juanzhang and ttklwxx for International Grandmaster Testing.

• maomao90, juju527, zimpha, NamelessStory, xuanquang1999, CrTsIr and EasonTAO for Grandmaster Testing.

• SATSKY_2024target_IGM, lanhf, Hank2019 and Yakumo_Ran for Master Testing.

• DaniraSilla and kriepiekrollie for Candidate Master Testing.

• raulandreipop, micho, alwyn, ArgintLaAnu, IssamOtoz and jakao for Expert Testing.

• CLown1331 for Pupil Testing.

• You for participating the round.

• MikeMirzayanov for Codeforces and Polygon systems.

Especially, I would like to thank errorgorn for his great contribution to the round, njwrz for providing user solutions for all the problems, Kevin114514 for making the announcement and tutorial more readable.

Finally and most importantly, I would like to thank PersistentLife for helping me with everything patiently all the time. This round can't happen without him.

The main character of the problems will be Jellyfish, a sweet little girl. 🍏🍏🍏

Score distribution:

• Div.1: $$$500$$$ − $$$1250$$$ − $$$1500$$$ − $$$2250$$$ − $$$3000$$$ − $$$4000$$$ − $$$5000$$$

• Div.2: $$$500$$$ − $$$1000$$$ − $$$1000$$$ − $$$1250$$$ − $$$2000$$$ − $$$2250$$$ − $$$3000$$$

Good Luck & Have Fun! 🔥🔥🔥

UPD1: Editorial is out.

UPD2: Congratulations to the winners!

Hello, Codeforces!

ognjentesic, wxhtzdy, OAleksa, AndrewPav, Acanikolic73 and I are glad to invite you to the Codeforces Round 900 (Div. 3).

It starts on Sep/26/2023 17:35 (Moscow time)

You will be given 7 problems and 2 hours and 15 minutes to solve them.

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

Also note that there will be a 12 hour open hacking phase after the round.

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, the round will be rated for you.

Problems have been created and prepared by AlphaMale06, ognjentesic, wxhtzdy, OAleksa, AndrewPav, Acanikolic73, and Vladosiya.

We would also to thank:

1. Vladosiya for the amazing coordination and help with preparing a balanced problemset, and for giving us the opportunity to create a Div. 3 round.
2. MikeMirzayanov for the amazing Polygon and Codeforces platforms.
3. JovanB, abc864197532, sevlll777 for red testing
4. NemanjaSo2005, n0sk1ll, allllekssssa, Alexdat2000, misorin, Hyperbolic for yellow testing
5. DAleksa, ljuba, alex.kudryashov for purple testing
6. MihailoT, SashaT9, BULLMCHOW, Chrisedyong, --tofu-- for blue testing
7. Andrijanikolic73, Mihajlo18, UrosNedic, Klaus26, Escaquejant, mxon, max0n for cyan testing
8. Budimmm for gray testing

Also a very special thanks to the most dedicated tester I have ever seen, NemanjaSo2005.

I wish you luck, and hope you like the problems and learn from them.

Update: Editorial is out.

Congratulations to the winners:

Unofficial:

1. jiangly

2. SSerxhs

3. BucketPotato

4. neal

5. risujiroh

Official:

1. hackerjohn

2. wahb

3. kutcoder

4. Sxy_Limit

5. not_rainboy

Hello, Codeforces!

I am pleased to invite you to participate in Codeforces Round 899 (Div. 2), which will be held on 25.09.2023 17:35 (Московское время).

All problems were written and prepared by me.

You will be given 5 problems, and one of them is divided into two subtasks. You will have 2 hours to solve them.

I would like to thank:

• irkstepanov for excellent coordination and Russian translation!

• Golovanov399 for providing useful feedbacks.

• kizen for helping me much with one problem of the contest.

• ko_osaga for Nutella testing.

• leinad2, Numbering, qwerasdfzxcl, kizen, Golovanov399 for Red testing.

• Kaling, Mingyu331, chaeyihwan, Kawaii2DIdolOfGSHS, azberjibiou, mjhmjh1104, DELTARUNE, wuhudsm, as_dfsdf for Orange testing.

• unordered_map, alex0211, gs20036, namolbbaemi, eeeDA, nlog for Purple testing.

• andyandy, JaewonOh, kongum, Coruncanius, ez_code, fs_edge, chromate00 for Blue testing.

• Hanlana18, papergundam, sjmjys954646 for Gray testing.

• MikeMirzayanov for great Polygon and Codeforces platforms!

• And last but not least, You for participating in the round!

Score distribution: $$$500 - 1000 - 1500 - 2000 - (2000 + 2000)$$$

Good luck and enjoy the round!

UPD: Editorial is out.

UPD2: Congratulations to the winners!

Official Contestants

1. Lycorisqwq
2. zepto
3. vjudge39
4. Beelzebub_blue
5. _t_W_

Official + Unofficial Contestants

1. ksun48
2. jiangly
3. antontrygubO_o
4. Sugar_fan
5. KumaTachiRen

Hello Codeforces!

On Sep/24/2023 17:35 (Moscow time) Educational Codeforces Round 155 (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, Ivan BledDest Androsov, Maksim Neon Mescheryakov, Roman Roms Glazov 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:

Scholarships for Master's students in Computer Science and Data Science are available in Harbour.Space University Barcelona campus!

Scholarship Summary:

• Fully funded scholarship (29.900 €/year) to study a Master’s degree in Data Science or Computer Science for two years
• Successful applicants will become part of the University’s “Talent pool” and will be shown to the sponsoring companies. In case the candidate is picked for the Work&Study Program from our industry partner, the student starts an internship with a commitment to study 3 hours/day and work for 4 hour/day

Please note preselected candidates will be requested to pay a non-refundable application fee of 85€ to study at Harbour.Space University.

Candidate’s commitment:

You will complete 15 modules (each three weeks long) in one year. The daily class workload is 3 hours, plus homework to complete in your own time.

Candidate’s requirements:

• Bachelor's degree in the field of Mathematics, Statistics, Data Science, Computer Science or similar
• English proficiency
• Advanced knowledge and experience in Python, SQL, Spark/Scala, and bash
• Experienced use of Big Data technologies: Spark, HDFS, Kafka, etc.
• Hands-on experience with Data Science techniques: feature engineering,
• Strong ML knowledge
• Strong Software Engineering Background
• Problem-solving aptitude

UPD: Editorial is out