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, cadmiumky, satyam_343, 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. mnbvmar
2. ecnerwala
3. ainta
4. ksun48
5. ekzhang

Div2:

1. hbi1998
2. Nutella3000
3. calabash_fool
4. ahgus89
5. 1207koo

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

Hello CodeForces!

Me, happypotato1207 and nicholask are excited to invite you to participate in Codeforces Round #822 (Div. 2). It will start at Sep/23/2022 15:05 (Moscow time). 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, ta4p, ACGN, Mike4235, brianlee.lck, JeffreyLC, prvocislo, ITO, dbsic211 marvinthang, QuangBuiCP, 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. 822E-Liar
4. Second_Brave_Niuniu
5. hitonanode

Official:

1. GOI_Official
2. 822E-Liar
3. Second_Brave_Niuniu
4. Sand_Emperor
5. steven14414

Hello Codeforces!

We invite you to Codeforces Round #821 (Div. 2) starting on Sep/19/2022 17:35 (Moscow time). The round is rated for users whose rating is lower than 2100.

All problems were mainly created and prepared by me. One problem is revised by mejiamejia. I would also like to thank:

• MikeMirzayanov for Codeforces and Polygon platforms,
• KAN for helping preparation of the round,
• Arpa for coordinating and reviewing the round,
• mejiamejia for developing one problem and a lot of advices,
• satyam_343, 74TrAkToR, MagentaCobra, cadmiumky, Andreasyan, darkkcyan, Vladithur, Etherite, welleyth, mjhmjh1104, emorgan5289, jeroenodb, oolimry, willy108, uuzlovetree, abc864197532, tibinyte, -skyline-, TomiokapEace, gyh20, SSerxhs, djq_cpp, Lucina, ugly2333, ITO, ak2006 for testing the problems and giving feedback, especially Vladithur for trimming the statement,
• All users for participating in the contest!

You will be given 5 problems with one subtask and 2 hours to solve them. The score distribution will be announced closer to the start of the round.

Good luck, and have fun!

UPD1: Score distribution is 500 — 1000 — 1500 — ( 1500 + 750 ) — 2750.

UPD2: System testing has been finished. Congratulations to the winners!

Out of competition

1. Geothermal
2. SSRS_
3. tabr
4. jiangly
5. tute7627
6. m_99
7. kotatsugame
8. Ethan_Rao
9. maspy
10. smax

Official participants

1. dengTianliang
2. i_will_be_less_than_blue
3. tlvvpdus
4. PokerCareer
5. casual11
6. wildwolf_ptyzs
7. Puranya_
8. 963noah
9. LovelyEther
10. warner1129

UPD3: Editorial is published.

Hello, Codeforces!

We are happy to invite you to an exciting online event: ICPC 2022 Online Challenge powered by HUAWEI，which will start on September 15, 2022, 00:00 UTC (UTC+0).

In this Challenge, you will have a unique chance:

• to compete for 2 weeks online during the challenge
• to solve 1 or 2 problems prepared by different business domains of HUAWEI
• to win amazing prizes from HUAWEI!

As a special prize, HUAWEI together with ICPC Foundation will provide the travel trip to the 46th Annual ICPC World Finals in a guest role to the 2 winners (1 winner for each problem)!

Everyone is welcome to participate. It is an individual competition. ICPC 2022 Online Challenge powered by HUAWEI (open to the public): September 15 — September 30, 2022, 00:00 UTC (UTC+0)

This time HUAWEI has prepared 2 challenging tasks for you from different business domains – Data Communication and Cloud.

You are free to choose which problem you would like to solve, and you are also welcome to solve both problems, but please remember the total runtime of both rounds, which start simultaneously, is 15 days only. We hope you'll enjoy this complex yet very exciting Challenge!

Each problem will have its own scoreboard and its own prize fund, so this is a unique chance for you to win double prizes for two solved problems!

Problem No 1: Optimal graph partitioning for fast routing

This problem comes from HUAWEI’s Data Communication business domain, in which routing algorithms have always been a critical issue. In the future, as more and more communication devices are connected to networks, data communication will face an interconnected network formed by ultra-large-scale network devices.

In this challenge, data communication experts of HUAWEI will provide you several network topologies. By dividing them into abstract domains, you need to scale down these topologies and enable quick route calculation, so that fast route convergence can be implemented on large-scale networks. Domain division must address the optimal routing and network scale constraints, so a routing algorithm that effectively divides domains while also meeting these constraints is the core of the algorithm design.

Problem No 2: Topology-Aware VM Placement

This problem comes from another HUAWEI’s business domain – Huawei Cloud. To win the competition in cloud computing market, major cloud service providers are focusing on improving the utilization of cloud resources, as this will allow to reduce the cost of cloud services. It is estimated that even a 1% increase in cloud service resource utilization can save millions of dollars in costs. The optimization of resource utilization, in turn, requires the development of advanced algorithms and technologies for cloud resource management.

The virtual machine (VM) placement algorithm considered in this contest is one of these critical algorithms, which is used to select a physical machine for running a user VM. Since VM requests arrive dynamically, this algorithm works in online fashion. The main goal is to maximize the number of successfully placed VMs. As the algorithm runs on a resource pool of fixed size the more requests are allocated, the less resources are wasted and the more resource efficient is the algorithm. A secondary goal is to maximize the number of VMs placed without violation of additional soft constraints, as it improves the cloud user experience.

Prizes

Grand Prize (Rank 1):
Problem 1: 15,000 EUR + the travel trip to the 46th Annual ICPC World Finals in a guest role
Problem 2: 15,000 EUR + the travel trip to the 46th Annual ICPC World Finals in a guest role

First Prize (Rank 2- 6):
Problem 1: 8,000 EUR
Problem 2: 8,000 EUR

Second Prize (Rank 7- 16):
Problem 1: 3,000 EUR
Problem 2: 3,000 EUR

Third Prize (Rank 17 – 46):
Problem 1: HUAWEI FreeBuds
Problem 2: HUAWEI FreeBuds

* If the allocated HUAWEI Challenge prize cannot be delivered to your region for any reason it may be replaced by another prize of the same value (if no legal restrictions), at the discretion of the sponsor.

Challenge Rules and Conditions

By participating in this Challenge, you agree to the Challenge Rules and Conditions of Participation

Good luck, we hope this will be fun!

Hello! Codeforces Round #820 (Div. 3) will start at Sep/12/2022 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. One of the problems in this round is interactive. Don't forget to read the guide on interactive problems.

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, SixtyWithoutExam and Vladosiya.

We would like to thank: Kniaz, BledDest, Svyat, Be_dos, Timur2006, FelixDzerzhinsky, alphabet321, FedShat, vsinitsynav, Jostic11, HamletPetrosyan, _Roma_, KKT_89, ABalobanov, lightseba, powergee101, DafuQ_o and AshrafEzz for testing the contest and valuable feedback. List of testers will be updated.

Good luck!

UPD 1:

We are in the middle of the round (and missing Gornak40 and Gol_D).

UPD 2: Editorial

Hello Codeforces!

On Sep/08/2022 17:35 (Moscow time) Educational Codeforces Round 135 (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!

UPD: Editorial is out

Hello Codeforces.

Unfortunately a few hours after the end of Round #819 we were pointed out that one of the problems was stolen from another online judge.

Codeforces team strongly condemns such an action from the author. By no means is this acceptable behavior. This is the first and the most important rule of problem making: your problem should be new up to your best knowledge.

A lot of people put lots of effort into creation of every single round. You can find these people mentioned in the announcements and they indeed deserve these acknowledgments. And yet a single cowardly decision can ruin this huge work and experience of thousands of participants.

In this particular case the copied problem was not widely known, and it seems that this made little or no impact on the course of the round. Nevertheless, we stick to the decision that in such case the round cannot be considered successful, and thus no rating changes can be applied. We will also remove the problem from the round and from the problemset as well as blacklist the author.

We hope that this case will be a lesson for future authors and this situation does not repeat in the future.

Hello Codeforces!

Grimoire of Code, the official Competitive Programming club of IIT Kharagpur, is happy to invite everyone to take part in Codeforces Round #819 (Div. 1 + Div. 2) and Grimoire of Code Annual Contest 2022 which will take place on Sep/06/2022 17:35 (Moscow time). This round will be rated for everyone.

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

The problems have been authored and prepared by Grimoire of Code members Anubhav anubhavdhar Dhar, Debajyoti little_angel Dasgupta, and Mainak Newtech66 Roy.

We'd like to thank all the people who made this round possible:

• Artyom123 for their supercalifragilisticexpialidocious coordination + Russian translations!
• shivanshshukla60 for being the one and only leamder. No, "leamder" is not a typo
• harsh639 and rishit3234 for behind-the-scenes work and proposing tasks that did not make it to the final problemset.
• All of our testers: AwakeAnay, TimeWarp101, naman1601, preyam, fugazi, kasparovian, amul_agrawal, TheOneYouWant, AlbertoTDNeto, thenymphsofdelphi, physics0523, Um_nik, Absyarka, MayankAg, hackerbhaiya, Pratyush1606, sqrt_pi, for testing and providing useful feedback.
• MikeMirzayanov for great platforms Codeforces and Polygon.

We hope everyone will enjoy the contest.

See you on the leaderboard!

About Grimoire of Code:

Grimoire of Code is the official Competitive Programming club of IIT Kharagpur created by and for competitive programming enthusiasts. We promote competitive programming culture in our college, and provide a forum for interested minds to discuss their thoughts and ideas. We also conduct mock coding rounds for placements and internships in Indian colleges.

You can check out our Facebook page here.

You can check out the problems from last year's Annual Contest here.

Updates

UPD1: The contest duration has been extended to 2 hours 15 minutes.

UPD2: Score distribution: $$$500-1000-1500-2000-2250-2750-3250-3500$$$

UPD3: Congratulations to the winners!

1. Benq
2. tourist
3. jiangly
4. Maksim1744
5. kotatsugame
6. tatyam
7. TLEwpdus
8. gyh20
9. turmax
10. Radewoosh

UPD4: Editorial (editorial for F will be added soon) It is now added.

UPD5: The contest is unrated due to problem copying. Details.

Hello, Codeforces! 🤗

We are happy to invite you to participate in COMPFEST 14 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred) on . COMPFEST is a national ICPC-style contest for university students in Indonesia.

The problems are written and prepared by Pyqe, steven.novaryo, Nyse, muhammadhasan01, gansus, nandonathaniel, FerdiHS, TakeMe, and NeoZap.

We would also like to thank:

• KAN for helping to host the mirror round;
• rama_pang (rama_pang, Zappeko, Berted), pengzoo (DishonoredRighteous, golikovnik), bukanYohandi, bry_rp, Drew_, and david.alexander01 for testing the contest and providing us very useful feedback;
• Universitas Indonesia, all the local committees, administrators, and managers of the whole COMPFEST event;
• prabowo for existing;
• fushar for the Judgels platform used in the official contest; and finally
• MikeMirzayanov for the amazing Codeforces and Polygon platform!
• Extra thanks for Pyqe for the dedication and effort 💪 in COMPFEST 14, as without him, the contest would not exist.

The contest will last for 5 hours and consist of 13 problems. While it is preferred to participate in a team, individual participation is also allowed. The problems themselves are expected to be easier than ICPC Regional contest.

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. Good luck!!

UPD: Editorial is up!!