Hello Codeforces!

On Apr/20/2023 17:35 (Moscow time) Educational Codeforces Round 147 (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 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!

Are you curious about the latest AI advancements and how they impact our world? Do you want to know more about how AI-based methods, especially in Natural Language Processing, are revolutionizing the way we work and interact with technology?

Space.Talks Present: Radoslav Neychev, AI Enthusiast, Researcher, and Machine & Deep Learning Professor.

Radoslav, a top-tier data scientist with extensive experience in Deep Learning and Reinforcement learning techniques, is coming to our Harbour.Space Barcelona Campus to give a talk on this topic. If you can't make it there, you can join the conversation, as we will stream it live on our YouTube channel here.

In this Space.Talk, Radoslav will share his expertise on how AI is changing our everyday lives and why it's important for both technical and non-technical specialists to understand the basics of how AI works. Plus, he'll also answer important questions about AI research and its future implications.

Mark your calendar for Thursday, April 20th, at 12hrs CET, and join us for an engaging conversation. Whether you're an experienced tech expert or just starting to explore the world of coding, this talk is for you!

And remember that we are always looking for the best and brightest! If you want to learn from industry experts like Radoslav, check out the scholarships we are offering and build a brighter future with us!

UPD: Editorial is out

Hello Codeforces!

UPD. I_love_natalia crashed the checker by his maze with $$$10^9$$$ moves. The problem is resolved now and all of the solutions rejudged. Scoring is changed. More info

UPD 2: The official site https://buglab.ru/ was updated. See comment.

UPD 3: The checker has been speeded-up by mfv in $$$2.2$$$ times (in comparison with my checker. The new speed is equal to $$$4$$$ seconds for a $$$10^9$$$ moves in codeforces "Custom Invocation"). Current standings:

1. $$$17\cdot 10^9$$$ — sas4eka;
2. $$$14\cdot 10^9$$$ — I_love_natalia;
3. $$$6.8 \cdot 10^9$$$ — maxplus (on the buglab: $$$11.3 \cdot 10^9$$$).

UPD 4: I updated the checker: now mazes up to $$$42$$$ billions are supported before checker got TL. Time limit of checker on codeforces platform is equal to $$$1$$$ minute. I submitted the maze with number of moves equal to $$$42.015.084.960$$$ and the result has been calculated in 59799 ms. Maybe someone can calculate the answer faster?

I'm happy to invite you to an unofficial mirror of Bug Game. In this game you need to generate a $$$21 \times 31$$$ maze with the maximum number of bug's moves to get out. The bug moves not optimally and you will see a description of algorithm of its movement in the statement of this problem. Based on given algorithm you will be able to create a maze and submit it.

Privacy: your solutions (your mazes) will be visible only for mfv.

Invitation link: click here

Date: April 18, 2023, 00:00 UTC+3

Duration: 2 weeks, then upsolving and virtual participation.

Scoring: if you will be able to generate the maze with $$$X$$$ moves to get out, then your solution will get $$$\frac{x}{10^5}$$$ points.

Official Russian site of Bug Game: click here

Hello, Codeforces!

This Saturday VIII Lipetsk Team Olympiad, a competition for high school students from all over the country, will be held in Lipetsk. Maybe you participated in previous Codeforces rounds based on our problems (rounds 643 and 791).

The round will start at 15.04.2023 12:05 (Московское время) and will last for 2 hours. Please notice the unusual time. Each division will have 6 problems. The round will be held according to the Codeforces rules and will be rated for both divisions.

Problems were proposed and prepared by Um_nik, DishonoredRighteous, FairyWinx, golikovnik, teraqqq, grphil, Kon567889, TeaTime, Tikhon228 and dshindov.

I would like to thank Artyom123 for great round coordination and our testers: Ormlis, bashkort, Umi, I_LOVE_ANTON_DONBASS, Egor.Lifar, iakovlev.zakhar, Mangooste, Siberian, SomethingNew, stepanov.aa, talant, rt3, towrist, Aaeria, Alexdat2000, qxforever, Renatyss, Renedyn, sevlll777, towrist, valerikk, Tiagodfs, wiz_cs, Setsuna, ezraft, Gornak40, HunterXD, kbats183, Nathan_McKane, nik_sn, Nitelike, Tilt, ak2006, KiruxaLight, 9kin.

Of course, I would like to thank all Codeforces team for this beautiful platform!

Scoring distribution will be announced later.

I hope you will enjoy our problems. Wish you good luck and high rating!

UPD: Scoring distribution:

Div.1: 750 – 1250 – 1500 – 2000 – 2750 – 3000

Div.2: 500 – 1000 – 1750 – 2000 – 2500 – 3500

UPD: Winners!

Div 2:

• yy_chen
• dengtingyu12138
• keyurchd_11
• Lyamzin_alexandr
• 39_w_M9

Div 1:

• BurnedChicken
• Radewoosh
• turmax
• yzc2005
• tourist

UPD: Editorial is available here

Hello, Codeforces.

I have implemented automatic translation of problem statements in Polygon (yes, yes, through ChatGPT). Here's an example of how to use it:

• Suppose we have a problem statement only in Russian and we want to have it in English as well.

• Create an empty problem statement in English.

• Go to the bottom of the problem statement and click on "Add automatic translation."

• In the popup window, you can choose the original language for translation (we only have Russian, so there's nothing to choose) and the section of the problem statement to translate (by default, it usually selects the appropriate option — translate everything).

• Click the "Translate" button.

• Wait for ChatGPT to translate the text (it may take up to a couple of minutes).

• When the translation is ready, it will be loaded into the popup window.

• Click "Save Translation."

• Done.

• Remember to proofread the statement yourself. Although it's a quality machine translation, it's still a machine translation.

One useful thing to note is that this method of translation miraculously preserves most of the LaTeX markup.

When using it, remember that the API is not free. I have set quotas, and if they are exceeded, I will have to turn off the feature. I hope this doesn't happen.

There are a few more ideas on how to use ChatGPT for peaceful purposes. Don't go too far.

Hello, Codeforces community!

We are happy to invite you to participate in National University of Singapore (NUS) CS3233 Final Team Contest 2023 Mirror on Monday, April 10, 2023, at 09:35 UTC. CS3233 is a course offered by NUS to prepare students in competitive problem solving.

The contest is unofficial and will be held in Codeforces Gym. Standard ICPC rules (Unrated, ICPC Rules, Teams Preferred) apply. The contest is unrated. Note the unusual starting time.

The problems are written and prepared by user202729_, rama_pang, and pooty.

We would also like to thank:

• Dr. Steven Halim for coordinating and teaching the CS3233 course;
• user202729_ and rama_pang as teaching assistants;
• stack.py (Pyqe, hocky, faustaadp) for testing the contest;
• errorgorn for existing;
• the Kattis team for the platform used in the CS3233 course and in the official contest;
• Codeforces Headquarters for letting us announce on the main page; and finally
• MikeMirzayanov for the amazing Codeforces and Polygon platform!

The contest will last for 5 hours and consist of 14 problems. While it is preferred to participate in a team, individual participation is also allowed.

The problems themselves may be quite standard as they are targeted toward those who have just learned competitive problem solving. However, we have also included a few challenging problems for stronger teams, such as ex-IOI or ICPC participants taking part in the course as well. So, the participants can expect a good mix of problems of varying difficulty levels, that we hope can be educational!

We hope you will enjoy and have fun in the contest. Good luck!

UPD: Contest is over! Editorial is up!

Congratulations to P+P+P (998kover, 244mhq, 353cerega) for the win!

Happy Easter, Codeforces! Sadly the round will not be Easter themed :(

We (arvindf232, culver0412, snowysecret, AHappyPotato, jerryliuhkg) are delighted to invite you to participate in Codeforces Round 865 (Div. 1) and Codeforces Round 865 (Div. 2), which will take place on Apr/09/2023 17:45 (Moscow time). Participants with a rating lower than 1900 will participate in Division 2, while participants with a rating of at least 1900 will participate in Division 1. Notice the unusual starting time.

All the problems were authored and prepared by arvindf232, culver0412, snowysecret and AHappyPotato. Huge thanks to the following people, without whom the round would not be possible:

• Artyom123 for excellent coordination and translation of statements.
• KAN for help with round preparation.
• jerryliuhkg for problem proposals which didn't make it to the final problem set.
• gamegame, dorijanlendvaj, abc864197532, ShuiLaoshi, ACGN, Rekaxem, xiaoziya, Perpetually_Purple, prvocislo, Qingyu, JeffreyLC, wyhong3103, Nahian9696, NemanjaSo2005, Dakto, triple__a, Singinginginging, Imakf, Ritwin, TomiokapEace, dbscts, mariowong123, jerryliuhkg, Flower08, Codula, prabhav_, rsj, __jk__, Aaeria, DBSHoShunNgai, Tutis, ak2006 for testing and valuable feedback.
• rsj for providing a nicer solution to one of the problems.
• MikeMirzayanov for Codeforces and Polygon platforms.
• You, for participating!

In both divisions, you will have 2 hours and 15 minutes to solve 6 problems. One of the problems is interactive, please see the guide of interactive problems if you are not familiar with it.

Wish you good luck and high ratings!

UPD1: Score distribution is as follows:

• Div. 1: 500-1250-1750-2500-3000-3500
• Div. 2: 500-1000-1250-2000-2500-3250

UPD2: Editorial

UPD3: Congratulations to the winners!

Hello, Codeforces!

AC-Automation and I rui_er are glad to invite you to participate in Codeforces Round 864 (Div. 2), which will be held on Apr/08/2023 17:05 (Moscow time). Please note the unusual start time.

This round is rated for the participants with ratings strictly lower than 2100. You will be given 6 problems and 2 hours to solve them. All the problems are prepared by AC-Automation and me.

We would like to thank:

• darkkcyan for a perfect coordination and help with the problem preparation.
• AC-Automation for providing some rejected problems and helping me a lot in preparation.
• zplqwq for polishing English statements and editorials.
• Alexdat2000 for the Russian translations.
• N_z__, HQJ2007, 2_3_3, ShmilyTY, blobugh, fishy15, Celtic, 10circle, LXH-cat, Hanghang007, wsc2008qwq, KaguyaH, XG0000, Astolfoo, 5ab, Electric_Field, MagentaCobra, RedLycoris, Everule, ieeqwq, Dominater069, Sol1, happydef, geospiza, amenotiomoi, zengminghao, yoy68, DitaMirika, yzy1, vectorwyx, vinfat, AliceLiCF, le0n and ak2006 for testing this round and providing valuable feedbacks.
• MikeMirzayanov for the great Codeforces and Polygon platforms.

• You

  for participating in this round.

There will be a finite number of interactive problems, so please see the guide of interactive problems if you are not familiar with it.

The main character of the problems is Li Hua.

Statements and editorials will be available in Chinese (Simplified) after the contest.

This is our first round. We've tried our best to make the round enjoyable. We are looking forward to your participation and hope you gain a non-negative delta in this round.

UPD1: Score distribution: 500 — 1000 — 1500 — 1750 — 2250 — 3000.

UPD2: Editorial is out.

UPD3: Statement in Chinese and Editorial in Chinese are out.

UPD4: Congrats to the winners!

Div.2:

1. syf2008
2. elizazh
3. zhouzizhe
4. psz1
5. wnmrmr

Div.1 + Div.2:

1. jiangly
2. heno239
3. SSRS_
4. BurnedChicken
5. Sugar_fan

Also congrats to the only div.2 participant who solves problem F: reborn2023!

Hello Codeforces!

On Apr/06/2023 17:35 (Moscow time) Educational Codeforces Round 146 (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 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!

Once again, it is time for another exciting scholarship opportunity from Harbour.Space!

We are looking for talented individuals who want to launch their careers in Cyber Security with a 50% scholarship to study in Barcelona.

If you love technology and looking for an exciting career, then Cyber Security might be for you!

But don't just take our word for it — as a member of the Codeforces community, you know the value of continuous learning and growth. The Cyber Security master’s programme at Harbour.Space responds to a growing market need, driven by increasing threats of global cyberwarfare, for cyber professionals with advanced training in both defensive cybersecurity and offensive cyber actions. The programme is designed to provide the knowledge, skills, and abilities required to perform critical cybersecurity tasks successfully.

Requirements:

• Bachelor’s Degree
• Professional fluency in English
• Your CV in English

What you will learn:

• Applied Threat Intelligence
• Threat Hunting
• Reverse Engineering and Malware Analysis
• Digital Forensics and Incident Response
• Pentesting and Ethical Hacking
• Hardware Conception of Processing Modules for the IoT
• Networks and Protocols
• Crisis Management and Communications
• BlockChain and IAM
• Soft Skills: Team Building, Presentation Skills and Meeting Facilitation
• And more

Make sure to apply before April 30th, 2023, to be eligible for the scholarship and reduced application fee.

Keep in touch and follow us on LinkedIn for more scholarship opportunities. And follow us on Instagram to evidence student life, events, and success stories from students.

We are always happy to see Codeforces members join the Harbour.Space family.

Apply now to learn from the best in the field and take your career to the next level!

Good luck on your round, and see you next time!

Harbour.Space University

UPD: The contest is unrated. We apologize for the inconvenience.

UPD: Editorial is out