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,
• satyam343, 74TrAkToR, MagentaCobra, valeriu, Andreasyan, darkkcyan, Vladithur, Etherite, welleyth, mjhmjh1104, emorgan, 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. LikeStrangers
2. i_will_be_less_than_blue
3. tlvvpdus
4. PokerCareer
5. casual11
6. wildwolf_ptyzs
7. MahiruShiina
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, senjougaharin and Vladosiya.

We would like to thank: Kniaz, BledDest, Svyat, Be_dos, Timur2006, FelixDzerzhinsky, alphabet321, FedShat, vsinitsynav, Jostic11, erankyun, _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!
• shivansh1102 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, gansixeneh, nandonathaniel, FerdiHS, TakeMe, and NeoZap.

We would also like to thank:

• KAN for helping to host the mirror round;
• rama_pang (rama_pang, yz_, 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!!

Hello Codeforces!

flamestorm, MikeMirzayanov and I want to invite you to Codeforces Round 817 (Div. 4).

It starts on 30.08.2022 17:50 (Московское время).

The format of the event will be identical to Div. 3 rounds:

• 5-8 tasks;
• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behaviour. To qualify as a trusted participant of the fourth 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 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: sandry24, SlavicG, tibinyte, Gheal, qwexd, haochenkang, TimDee.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

UPD 1: The contest is delayed by 15 minutes.

UPD 2: The opinions of testers about the order of problems are very contradictory. Please do not rely heavily on the order of problems in the round and read all the problems. Good luck!

UPD 3: Editorial is out!

Hello Codeforces!

On Aug/27/2022 17:35 (Moscow time) Educational Codeforces Round 134 (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:

Harbour.Space University has partnered with Vodafone Business, a company rich in tradition that specializes in telecommunications and with Oneragtime, a fund-as-a-platform specialized in sourcing, financing and scaling early-stage tech startups from across Europe, to offer motivated tech talents Master’s degree scholarships in Data Science and Front-end Development with combination of work experience.

Candidates will be working on the following tasks:

Data Scientist at Vodafone:

• Data Science: Descriptive and predictive analytics: selection, definition, and execution of adequate algorithms, models, tests, visualizations, etc.
• Technology: Selection, definition, and execution of adequate programming languages/frameworks, file formats, data storage solutions, automatic data flows, etc.
• Architecture: Define and/or follow best practices for Big Data & amp; Analytics use cases while extracting, transforming, storing, and feeding data to/from different data sources using on-premises solutions as well as public cloud services.
• Management: Report to project managers, clients, external and/or internal teams. Estimate resources and timelines for different tasks and follow up during the full project life cycle.
• Innovation: Awareness of and continuous training in state-of-the-art techniques, models, frameworks, and technical approaches to be applied to Data Science activities.

Front-End Developer at Oneragtime:

• Define the technology stack / tools to be used in the frontend
• Suggest projects that will improve the product or code base
• Write scalable, maintainable, reusable, and well-tested software that adheres to best practices
• Make technical time estimation on future software deliveries
• Document solutions with clear and concise explanations
• Collaborate with Product Owners, Growth Hacker, UX / Product Designers

All successful applicants will be eligible for a 100% tuition fee scholarship (22.900 €/year) provided by Vodafone Business for Data Science and by Oneragtime for Front-end Development.

CANDIDATE’S COMMITMENT

Study Commitment: 3 hours/day ‍ 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.

Work Commitment: 4+ hours/day ‍ Immerse yourself in the professional world during your apprenticeship. You’ll learn from the best and get to apply your newly acquired knowledge in the field from day one.

University requirements

• Bachelor's degree in the field of Mathematics, Statistics, Data Science, Computer Science or similar
• English proficiency

Work requirements

Data Science:

• Advanced knowledge and experience in SQL, Python, Spark/Scala, and bash
• Experienced use of Big Data technologies: Spark, HDFS, Kafka, etc.
• Hands-on experience with Data Science techniques: feature engineering,

Front-end Development:

• Proficient in HTML/JSX, CSS, and with strong fundamentals in Javascript ES6
• Understand Vue
• Familiar with UX/UI principles: Figma
• Familiar with Webflow
• Expertise with Web pack, gulp, similar frontend build tools (npm)
• Proficient in unit testing tools e.g. JEST or similar tools
• Proficient in either Sass, LESS, TailwindCSS, Bootstrap, Flexbox, or similar tools
• Understanding of REST API
• Familiarity with Docker is appreciated
• Familiar with SQL works (Bonus: if you understand Postgre)

UPD: Editorial is out

Thanks a lot!

for Your participation

Hello, Codeforces!

We are glad to invite everyone to participate in Codeforces Round 816 (Div. 2), which will be held on Aug/20/2022 17:35 (Moscow time). The round will be rated only for the second division. You will have 6 tasks and 2 hours to solve them. We recommend you read all the problems.

Round is completely set by winter SIS (Summer Informatics School) students. During the camp we did our best to prepare interesting and creative problems. You can check previous rounds prepared by SIS students: Codeforces Round 815 (Div. 2), Codeforces Round #694, Codeforces Round #612, Codeforces Round #530

We are very thankful to

• task authors and developers: Vasilyev daubi Alexey, Denis Kapt Mustafin, Ivan __silaedr__ Podvorniy, Ilya ilyakrasnovv Krasnov, Evgenii pakhomovee Pakhomov, Mikhail MadProgrammer Zaytsev.

• to the wonderful teachers who made this round happen: Pavel PavelKunyavskiy Kunyavskiy, Dmitriy cdkrot Sayutin, Alesya AlesyaIvanova Ivanova, Konstantin kokokostya Makhnev

• Monogon for the great coordination, valuable advice, and patience

• KAN for the help during preparation of the contest

• Qwerty1232 for the help with the editorial

• testers for good proposals and important feedback: glebustim, kclee2172, AndreyPavlov, generic_placeholder_name, nor, TheScrasse, qualdoom, AlperenT, FairyWinx, vdv09, NToneE, KseniaShk, prost_sasha, agrayush13, kartikeyasri23, SomethingNew, and especially mejiamejia

• MikeMirzayanov and geranazavr555 for codeforces and polygon platform

Scoring distribution will be released before the contest begins

We hope that You will participate in our round, as well as in SIS!

Good luck and have fun!

UPD — Scoring distribution:

$$$500 - 1000 - 1750 - 2250 - 2750 - 3000$$$

The contest may contain interactive problems! Make sure to read this post.

UPD 2 — Editorial is out!

UPD 3 — Congratulations to the winners!

Official participants:

1. william556
2. fursuit
3. huge_waxberry
4. lbwhangbeateveryone
5. Longiseta

All participants:

1. jiangly
2. kotatsugame
3. hitonanode
4. ksun48
5. Rubikun