Hi everyone!

2022 Southeastern Europe Regional Contest will take place tomorrow, on December 10. The contest was prepared by bicsi, antontrygubO_o, theodor.moroianu, lungualex00, eudanip.

Good luck to the official participants!

There will be a mirror of this contest this Sunday, December 11, 08:00 UTC. It will be held by the link https://seerc2022.eolymp.io/.

We hope that you will enjoy the contest! See you on the scoreboard.

UPD1: Congratulations to the winners of SEERC!

This year, the contest was held on two sites, Ukrainian and Romanian.

Standings and Top 5 of Ukrainian site:

Standings and Top 5 of Romanian site:

Once again, we invite you to the mirror tomorrow.

UPD2: Editorial

UPD3: The contest was uploaded to the gym: 2022 ICPC Southeastern Europe Regional Contest. I will add results of official participants soon.

I am glad to invite you to AtCoder Grand Contest 059. This contest counts for GP30 scores.

• Contest URL: https://atcoder.jp/contests/agc059
• Start time: Sunday, December 4, 12:00 UTC
• Duration: 180 minutes
• Number of Tasks: 6
• Writer: antontrygubO_o
• Rated range: 1200+

The point values will be added soon.

I would like to thank:

• maroonrk for the amazing coordination of this round, for improving one problem, and for allowing me to host my third AGC (and third AGC in 2022). I also want to congratulate him on winning gold in ICPC 2021!
• maspy, dario2994, errorgorn, timreizin, Um_nik, 244mhq for testing the contest.
• MikeMirzayanov for the great Polygon platform

I really hope you will like the problems.

We are looking forward to your participation!

UPD1: Point values are $$$500$$$ — $$$700$$$ — $$$1100$$$ — $$$1100$$$ — $$$1400$$$ — $$$1900$$$

UPD2: Thanks for your participation!

The winners are:

1. ksun48

2. Petr

3. tatyam

4. hitonanode

5. tourist

We invite you to participate in CodeChef’s September Lunchtime, this Friday , 23rd September, rated for all. It is based on EJOI 2022, the second day of which takes place earlier on the same day. All EJOI participants were asked to not discuss the problems before the end of this contest, and to not participate in this contest. If you somehow got to know some of the problems, please, don't participate.

Time: 8:00 PM — 11:30 PM IST

Please note that the contest duration is unusual — 3.5 Hours.

Joining me on the problem setting panel are:

• Setters of EJOI: Ray MagentaCobra Bai, Anton antontrygubO_o Trygub, Matvey BigBag Aslandukov, Ihor Barichek Barenblat, Roman RomaWhite Bilyi, Jeroen Op de jeroenodb Beek

• Setters of extra problems for this contest: Utkarsh Utkarsh.25dec Gupta, Jeevan Jyot JeevanJyot Singh, Ashish Ashishgup Gupta

• Testers: I want to thank countless testers of EJOI: kostia244, welleyth, KostasKostil, VladProg, timreizin, Um_nik, 244mhq, errorgorn

• Contest Admins: Anton antontrygubO_o Trygub, Yahor 244mhq Dubovik, Jeevan Jyot JeevanJyot Singh

• Editorialist: Nishank IceKnight1093 Suresh

• I want to separately thank BanRussiaAtIOI for his colossal work put into the organization of EJOI.

The video editorials of the problems will be available for all users for 1 day as soon as the contest ends, after which they will be available only to Pro users.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Hope to see you participating. Good Luck!

We invite you to participate in CodeChef’s June Lunchtime, this Sunday, 19th June, Rated for All.

Joining me on the problem setting panel are:

• Setters: Anton antontrygubO_o Trygub, Yahor 244mhq Dubovik,Utkarsh Utkarsh.25dec Gupta,Alex Um_nik Danilyuk,Jeevan Jyot JeevanJyot Singh

• Tester: Harris Harris gamegame Leung

• Statement Verifier: Kanhaiya notsoloud1 Mohan

• Contest Admin: Anton antontrygubO_o Trygub, Yahor 244mhq Dubovik,Utkarsh Utkarsh.25dec Gupta

• Head Admin: Alex Um_nik Danilyuk

• Editorialist: Đặng Đoàn Kuroni Đức Trung

The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Hope to see you participating. Good Luck!

We invite you to participate in CodeChef’s June Cook-Off, this Sunday, 5th June, Rated for All.

Time: 8:00 PM — 10:30 PM IST

Joining me on the problem setting panel are:

• Setters: Anton antontrygubO_o Trygub,Utkarsh Utkarsh.25dec Gupta, TheScrasse TheScrasse,Lavish lavish315 Gupta,Devendra _Damon Singh,Milind jainmilind Jain, Alex Um_nik Danilyuk

• Tester: Harris gamegame Leung

• Statement Verifier: Nishank IceKnight1093 Suresh

• Contest Admins:Anton antontrygubO_o Trygub, Yahor 244mhq Dubovik

• Head Admin: Alex Um_nik Danilyuk

• Editorialist: Đặng Đoàn Kuroni Đức Trung

Also, announcing Scholarship for CodeChef Certification in Data Structure & Algorithms — More than 100 Indian participants in Divisions 1, 2, and 3 will win scholarships for the CodeChef Certification exam (discounted prices). Scholarship criteria can be found on the respective contest pages.

The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Hope to see you participating. Good Luck!

I hope you enjoyed the round.

While problem D1B was good for balance in Div1, it was too hard for balance in Div2. I apologize for this.

Problem D1B = D2D is by dario2994. Other problems are mine.

We will hold Codeforces Round #794 (Div. 1) and Codeforces Round #794 (Div. 2).

• Contest URLs: https://codeforces.com/contest/1685, https://codeforces.com/contest/1686
• Unusual start time: May/25/2022 20:35 (Moscow time)
• Duration: 135 minutes
• Number of Tasks: 6 for Div2, 5 for Div1
• Rated range: $$$(-\infty, 1899]$$$ for Div2, $$$[1900, \infty)$$$ for Div1
• Writer: antontrygubO_o
• Testers: golions, oleh1421, Geothermal, nor, TheScrasse, timreizin, emorgan5289, Um_nik, 244mhq, Kuroni, ak2006
• VIP-tester: errorgorn
• Coordinator and author of one problem without which round would be unbalanced: dario2994
• Creator of the amazing Codeforces and Polygon platforms: MikeMirzayanov

The point values will be:

Div2: 500 — 1000 — 1500 — 2000 — 2500 — 2500

Div1: 500 — 1000 — 1500 — (1500 + 1500) — 3500

We are looking forward to your participation!

UPD 1: Thanks to NEAR for supporting this round, details can be found in this post.

UPD 2: Editorial

UPD 3: Congratulations to winners!

Div1:

1. fantasy

2. jiangly

3. ecnerwala

4. gamegame

5. maroonrk

Div2:

1. lmqzzz

2. Teating_

3. lunchbox

4. Nida1097

5. demacia

We invite you to participate in CodeChef’s May Lunchtime, this Sunday, 15th May, rated for all.

Time: 8:00 PM — 11:00 PM IST

Joining me on the problem setting panel are:

• Setters: Mradul bhatnagar.mradul Bhatnagar, Manuj DarkSparkle Nanthan, Nishank IceKnight1093 Suresh, Valerio TheScrasse Stancanelli, Dan DannyBoy, Hazem zoooma13 Tarek, Hrishikesh hrishik85 Kelker, Yahor 244mhq Dubovik, Boris PuRpLe_FoReVeR Serenkov

• Tester: Harris gamegame Leung

• Head Admin: Alex Um_nik Danilyuk

• Statement Verifier: Nishank IceKnight1093 Suresh

• Contest Admins: Yahor 244mhq Dubovik, Anton antontrygubO_o Trygub

• Editorialist: Đặng Đoàn Kuroni Đức Trung

Also, announcing Scholarship for CodeChef Certification in Data Structure & Algorithms — More than 100 Indian participants in Divisions 1, 2, and 3 will win scholarships for the CodeChef Certification exam (discounted prices). Scholarship criteria can be found on the respective contest pages.

The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Hope to see you participating. Good Luck!

We invite you to participate in CodeChef’s May Cook-Off, this Sunday, 1st May, Rated for All.

Time: 8:00 PM — 11:00 PM IST

Note that from this month, Cook-Off and Lunchtimes will be held on Sundays instead of on Saturdays.

Joining me on the problem setting panel are:

• Setters: Yashodhan woxic Agnihotri, Utkarsh Utkarsh.25dec Gupta, Anton antontrygubO_o Trygub, Nishank IceKnight1093 Suresh, Daanish 7dan Mahajan

• Tester: Harris gamegame Leung

• Head Admin: Alex Um_nik Danilyuk

• Statement Verifier: Nishank IceKnight1093 Suresh

• Contest Admin: Anton antontrygubO_o Trygub

• Editorialist: Anton antontrygubO_o Trygub

A couple of extra words about the contest:

• All Div-1 problems have been set by me.

• The contest is harder than usually, so the duration is changed to 3 hours instead of 2.5 hours

• I hope everyone will enjoy the contest!

Also, announcing Scholarship for CodeChef Certification in Data Structure & Algorithms — More than 100 Indian participants in Divisions 1, 2, and 3 will win scholarships for the CodeChef Certification exam (discounted prices). Scholarship criteria can be found on the respective contest pages.

The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Hope to see you participating.

Good Luck!

I know that a lot of people here care about the war in Ukraine. If you are looking for ways to help, please, visit this link: http://linktr.ee/help_ukraine_global. Any support matters, any help matters.

Please, help to stop the bloody dictator of our neighbor.

UPD1: Another very good site

UPD2: With this website you can help to show Russians what's really going on in Ukraine. Props to this post.

UPD3: If your CF profile had country set to Ukraine at the moment of this post, and you haven't created Crowdforces account yet, you can do it by this link: https://nearcrowd.com/crowdforces, and receive 12 Near (which is around 100$ now).

You can find detailed instructions here. This document is available only in Ukrainian for now. Please, use this money for the maximum benefit.

We invite you to participate in CodeChef’s January Lunchtime, this Saturday; 29th January from 8:00 PM — 11:00PM IST.

The contest will be 3 hours long. There will be 5 problems in Div 1/2 and 6 problems in Div 3. It will be rated for all three Divisions.

Joining us on the problem setting panel are:

• Contest Admins: Yahor 244mhq Dubovik and Anton antontrygubO_o Trygub

• Head Admin: Alex Um_nik Danilyuk

• Tester: Takuki tabr Kurokawa

• Setters: Utkarsh Utkarsh.25dec Gupta, Daanish 7dan Mahajan, Soumyadeep soumyadeep_pal_21 Pal, Lokesh lucky_21 Singh, Anton antontrygubO_o Trygub, Daniel dannyboy20031204 Chiang, Manuj DarkSparkle Nanthan, Yahor 244mhq Dubovik

• Editorialist: Daanish 7dan Mahajan

The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

Problem Submission: If you have original problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Prizes:

• The top 10 Global Division 1 users will get $100 each.
• The top 100 Indian Division 1 will get Amazon Vouchers worth Rs. 1500 each.

Good luck and have fun!

P.S. I think that problems are interesting, I encourage everyone to try them!

It’s finally time for one of the biggest events in the competitive programming world. The SnackDown ‘21 Grand Finale is here.

The entire Grand Finale event is scheduled to be completed in two days — January 8 (Saturday), and January 9 (Sunday).

For the Finalists

All the information has been shared over email, but summarising — The Grand Finale will be spread over two days and will be a closed event accessible only to the finalists, and a few invited guests. The SnackDown 2021 Final contest will be held on Jan 9th between 6:30 — 10:30 PM (IST).

For the last time for this SnackDown, meet the panelists!

• Contest Admins: Anton antontrygubO_o Trygub and Yahor 244mhq Dubovik


• Head Admin: Alex Um_nik Danilyuk


• Testers: Ashley errorgorn Khoo and Andrew ecnerwala He


• Setters: Federico dario2994 Glaudo, Anton antontrygubO_o Trygub, Yahor 244mhq Dubovik, Yash PoPularPlusPlus Thakker, Arul flamestorm Kolla


• Statement Verifier: Ashley errorgorn Khoo

For the Community

For those who would like to have a taste of the SnackDown Final problems, we also have the SnackDown Final Parallel Unrated Contest scheduled for January 9, 2022, 6:30 PM — 10:30 PM (IST). The problems will be the same as the Finale. Since the main Finals will be a restricted session, the rank list can be viewed here. Note that the rank list will be frozen for the last hour, and will be resolved in the post-contest ceremony on YouTube.

The Grand Finale Closing & Crowning Ceremony

The SnackDown ‘21 Finale closing ceremony will start on Jan 9th at 10.30 PM IST. It will be hosted by Kamil Debowski and Ashish Gupta, who will be analyzing the contest problems and the strategies and performances of the participants. This is also where you can witness the moment of truth, the SnackDown ‘21 Grand Finale winner announcement! Everyone is cordially invited to the event, and we request you to set your reminders here.

As the last big contest of 2021 is over, I think it's time.

It seems that there were just more and more ad-hocs/"deeply analyze some complicated process" everywhere... But maybe you still liked something.

So, what were your favorite problems in 2021?

We are very glad to invite you to participate in SnackDown Elimination round! It will be rated for all participants.

60 participants will qualify for the finals from the Elimination round. They include:

• The top 25 participants from the Elimination round.


• Additional top 2 school participants


• Additional top 2 female participants


• Additional 31 Indian participants, including:
  • 10 top Indian participants
  
  
  • The next 15 Indian participants from the Elimination Round qualify provided they solve at least 2 problems.
  
  
  • 3 top Indian School participants
  
  
  • 3 top Indian Female participants

Those, who haven't advanced, are invited to participate in the Parallel rounds, which will be held for all divisions. All three rounds are rated too.

Time: 7:30 PM — 10:30 PM IST

Please note that the duration was initially written as 5 hours by mistake, it will actually be 3 hours. The Finals duration will also be less than 5 hours.

Joining us on the problem setting panel are:

• Contest Admins: Yahor 244mhq Dubovik and Anton antontrygubO_o Trygub


• Head Admin: Alex Um_nik Danilyuk


• Testers: Utkarsh Utkarsh.25dec Gupta (only for Div2 and Div3 problems), Tejas tejas10p Pandey (only for Div2 and Div3 problems), Yahor 244mhq Dubovik, Alex Um_nik Danilyuk, Anton antontrygubO_o Trygub


• Setters:
  • Elimination: Federico dario2994 Glaudo, Fedor Mediocrity Korobeinikov, Anton antontrygubO_o Trygub, Alex Um_nik Danilyuk
  • Additional Div3-Div2 problems: Nandeesh nandyboy Gupta, Utkarsh Utkarsh.25dec Gupta, Daanish Mahajan, Soumyadeep soumyadeep_pal_21 Pal, Surya evilbuggy Prakash, Srikkanth srikkanthr R, Mradul bhatnagar.mradul Bhatnagar


• Statement Verifier: Nishank IceKnight1093 Suresh (only for Div2 and Div3 problems), Yahor 244mhq Dubovik, Anton antontrygubO_o Trygub


• Editorialist: Taranpreet taran_1407 Singh (only for Div2 and Div3 problems)

Users who have qualified to participate in the SnackDown Elimination should not participate in the Parallel rounds.

The Div-1 Parallel round and the Elimination ranklists will be merged to determine the winners of the cash/Amazon voucher prizes.

If you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Hope to see you participating. Good luck and have fun!

Hi everyone!

2021 Southeastern Europe Regional Contest took place on November 21. Here you can view the full standings.

Congratulations to the winners of the contest!

There will be a Grand Prix of Southeastern Europe based on these problems this Sunday, November 28, 08:00 UTC. Here is the link to the OpenCup.

This year, the sets of SEERC and OpenCup are a bit different: OpenCup won't include a few easier problems from SEERC and will additionally include several harder problems. In addition, problems are shuffled, so don't follow the standings of the official contest too much.

The authors of the OpenCup set are eudanip, Um_nik, bicsi, RomaWhite, Andrei1998, and me, antontrygubO_o. After the contest, the editorials to both versions of the contest will be published, and both versions of the contest will be uploaded to the gym.

We hope that you will enjoy the contest!

UPD:

Editorials:

• SEERC (with some additional stats included)
• OpenCup

Both contests are uploaded to Gym:

• SEERC
• OpenCup

I am glad to invite you to AtCoder Grand Contest 055. This contest counts for GP30 scores.

• Contest URL: https://atcoder.jp/contests/agc055
• Start time: Sunday, October 31, 12:00 UTC
• Duration: 180 minutes
• Number of Tasks: 6
• Writer: antontrygubO_o
• Rated range: 1200+

The point values will be 400 — 700 — 900 — 1200 — 1500 — 1800

I would like to thank:

• maroonrk for an amazing coordination of this round, and for allowing me to host a contest on AtCoder for the second time
• AmShZ and maroonrk for a few great suggestions to improve some problems
• HIR180, AmShZ, DeadlyCritic, kpw29, zscoder, 244mhq, Um_nik for testing the contest
• 244mhq and Um_nik for regularly saying that the contest is well-balanced in terms of difficulty
• MikeMirzayanov for the great Polygon platform

Problem statements will be short again, and I really hope that you will like the problems. However, I have to warn you that contest will be closer to ABC than to AGC...

We are looking forward to your participation!

UPD1: Thanks for your participation!

The winners are:

1. ksun48

2. tourist

3. djq_cpp

4. hos.lyric

5. amiya

Special congratulations to tranquility , the only person to solve F.

Sadly, nobody got E in the contest time, though a few people were close. I encourage you to try it, or to read editorial, I think that it's the best problem I ever invented.

I hope you enjoyed the contest!

We invite you to participate in CodeChef’s October Cookoff, this Sunday; 24th October from 9:30 PM — 12:00AM IST.

The contest will be 2.5 hours long. There will be 7 problems in Div 1/2 and 8 problems in Div 3. It will be rated for all three Divisions.

Joining us on the problem setting panel are:

• Contest Admins: Ashish Ashishgup Gupta and Anton antontrygubO_o Trygub

• Head Admin: Alex Um_nik Danilyuk

• Tester: Danny Tlatoani Mittal

• Setters: Jeevan JeevanJyot Jyot Singh, Anshu _runtimeTerror_ Garg, Rahul sapora Kumar, Prasant prasant21 Kumar, Shiva Agnimandur Oswal, Sandeep dazlersan1 V, Anton antontrygubO_o Trygub, Utkarsh Utkarsh.25dec Gupta, Lavish lavish315 Gupta, Ashish 7KIRA1999 Kumar

• Statement Verifier: Trung Kuroni Dang

• Editorialist: Nishank IceKnight1093 Suresh

Video Editorialists and Translators will be added a bit later

Problem Submission: If you have original problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Prizes:

Global Rank List:

• Top 10 global Division One users will get $100 each.
• Non-Indians will receive the prize via money transfer to their account.
• Indian users will receive Amazon vouchers for the amount converted in INR.

Indian Rank List:

• Top ten Indian Division One coders will get Amazon Vouchers worth Rs. 3750 each.
• The rest in the top 100 will get Amazon Vouchers worth Rs. 1500 each.
• First-time winners in Div 2 who make it to the top 200 for the first time will get Amazon Vouchers worth Rs. 750 each.
• First-time winners in Div 3 players who make it to the top 200 for the first time will get Amazon Vouchers worth Rs. 750 each.

The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

Good luck and have fun!

P.S. Seriously, try it, I think problems are interesting :P

UPD1: Sorry for confusion, the duration is 2.5 hours.

This summer, me and 244mhq held a contest in Petrozavodsk Programming Camp. $$$1$$$ problem was provided by gepardo, and we are very thankful for that, and other problems were created by us, 244mhq and antontrygubO_o. This contest will be held as an OpenCup contest on September 19, 11:00 UTC+3.

I and 244mhq are friends for long time, since our years of participation at IMO, and it's 244mhq who introduced me to competitive programming. Therefore, we decided to call this contest GP of IMO.

Link (OpenCup login needed to participate)

I will publish the editorial here soon after the contest ends.

Good luck and have fun!

UPD1: Shame on me, I forgot to thank testers of this contest: gamegame, Geothermal, nitrousoxide.

UPD2: Editorial

//This is a short post motivated by the comment section of the last Div2 round (and of several rounds before)

Every problemsetter tries to make his contest as good as possible, and is upset when something goes wrong. Most problemsetters don't set contests for money, the payments are not worth the time and efforts spent on coming up with problems, preparing them, and hosting the contest. The most rewarding thing in this process in not the money, it's to see contestants enjoying your problems.

That's why feedback is so important. If the comment section is filled with comments praising the contest, setter will most likely want to come back with another contest, and if it's filled with hate and offenses, it's possible that setter will just give up on problemsetting and won't want to host another round.

This means two things.

First, if you liked the round, or some particular problem, why not to write a comment about it? I am sure that most setters would really appreciate it, and feel more motivated to come up with problems like the one you liked. Positive comments from high rated contestants, or from experienced problemsetters matter especially, but I rarely see positive comments from such users.

Secondly, we should try to avoid hateful comments, or unconstructive criticism. This doesn't mean that there shouldn't be any criticism, it is necessary to help setters to improve, but not all criticism is good. Below I will give several comments, which, in my opinion, aren't the best way to express your opinion about the contests. I won't mentioning authors of these comments, as I don't want to call anyone out, and I myself sometimes left not very cool comments.

What's the point of leaving such comments? How will this help setters to improve in problemsetting? These comments are not even telling what's exactly is wrong with the contest — it's just hate and a complete lack of respect to the setters (though I would consider Codechef comment as a compliment).

This is another type of comments — just saying that some particular problem was bad/shitty. However, this isn't much better, as this still doesn't help setter to improve much, it just discourages him from writing any problems in the future. If you are criticizing some problem, tell what exactly was wrong about it: was it well-known, standard, was it too caseworky, or too implementation heavy, maybe the constraints were too strict?

Again, I am not saying that criticism of contests in comments is bad. Here are some good examples (in my opinion).

They aren't disrespectful to the setters, and the authors of these comments are saying what exactly they didn't like about the contest, so that setter can avoid such mistakes in the future.

People may have different opinions about what's a good problem, or what makes a contest good, and setters won't always take all the criticizing comments into account when hosting their next round, but the feedback is still very important for improvement. So, when you leave negative comments, please try to not use them as an opportunity to call the author a stupid moron. It's better to tell what exactly went wrong, politely and respectfully, without any hate. There aren't that many problemsetters out there, so instead of telling people to stop writing problems, it's better to support them.

:)

Hi everyone,

I am happy to announce that the 2020 Southeastern Europe Regional Contest will take place on May 23 at 10 am UTC+3. The link to the live results will be published here after the start of the competition.

Moreover, later this day, at 4 pm UTC+3, there will be the Grand Prix of Southeastern Europe based on these problems. Because of the Grand Prix, we are asking the official contestants not to discuss the problems in public.

After it, we will upload the contest to the gym and publish the editorial. We hope that you will enjoy the contest.

Good luck to all participants!

UPD. SEERC standings

UPD2. Congratulations to the winners!

UPD3. Editorial

Thanks for your participation!

UPD4. The contest is available in gym:

2020-2021 ICPC Southeastern European Regional Programming Contest (SEERC 2020).

I am glad to invite you to AtCoder Grand Contest 052. This contest counts for GP30 scores.

• Contest URL: https://atcoder.jp/contests/agc052
• Start time: Sunday, March 7, 12:00 UTC
• Duration: 160 minutes
• Number of Tasks: 6
• Writer: antontrygubO_o
• Rated range: 1200+

I would like to thank:

• maroonrk for allowing me to host a contest on AtCoder and for the great coordination of this round
• 244mhq, gamegame, TheOneYouWant, hugopm, HIR180 for testing this round
• MikeMirzayanov for the great Polygon platform (only Polygon this time)

Statements are very short, and I really hope you will like the problems.

We are looking forward to your participation!

UPD 1: The point values will be 400-800-1000-1000-1500-2000, and the duration is decided to be 160 minutes

UPD 2: Congratulations to the winners!

1. ksun48
2. mnbvmar
3. tourist
4. Benq
5. Radewoosh

Thanks for your participation :P

As Morphy hasn't posted this yet, and as the last big contest of 2020 is over, I think it's time.

2020 was a hard year for all of us, but it still gave us a lot of great contests and, luckily, no notorious coincidences. So, what were your favorite problems in 2020?

We invite you to participate in CodeChef’s September Lunchtime, this Saturday, 26th September, from 2000 hrs to 2300 hrs IST.

Please Note — Unusual starting time. The Contest will begin at 2000 hrs instead of 1930hrs

The contest will feature 5 problems for 3 hours. I am author of all problems. I hope you will like them.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Joining me on the problem setting panel are:

• Tester: Alexander scanhex Morozov
• Statement Verifier: Jakub Xellos Safin
• Editorialist: Colin galen_colin Galen
• Admin: Ildar 300iq Gainullin
• Mandarin Translator: Gedi gediiiiiii Zheng
• Vietnamese Translator: Team VNOI
• Russian Translator: Fedor Mediocrity Korobeinikov
• Bengali Translator: Mohammad solaimanope Solaiman
• Hindi Translator: Akash Shrivastava

Prizes: The top 10 Indian and top 10 Global school students from ranklist will receive certificates and CodeChef laddus, with which they can claim cool CodeChef goodies. Know more here.

Good luck and have fun!

Hello everyone!

I finally decided to write some response/explain my view after all recent discussions of my problems and rounds I coordinate, and I would like to make a few points.

1. After some recent contests there were a lot of comments saying that Data structure problems should appear as easy problems (say, D2A-D2D in a Div2 of $$$6$$$ problems)

I don't think I agree with this. To begin with, I don't think that having Data Structure problem is a requirement for a good contest at all, not just in first few positions.

However, for positions D2A-D2D, I just don't see a way to properly include data structure problems. Take some Data Structure problem, it consists from two parts:

• Knowing/implementing the Data Structure
• Actually thinking about the problem, and how this Data Structure should be applied

The problem is, that even the simplest Data Structure (say, Segment Tree), makes the first part already at least D2D difficulty in a Div2 of $$$6$$$ problems. Now, if the second part is completely trivial, then the problem shouldn't be used in official CF contest (maybe in Educational Round only): implementation part can't be much harder than thinking part. If the second part isn't trivial, the problem can't be less than D2E. Therefore, I can't really see how can Data Structure problem appear on positions D2A-D2D.

Remark: Here I don't even count sets/maps as Data Structures.

2. A lot of people lately are sad because graphs, dp and all other topics don't appear now. Only constructives and ad hocs are left!

To begin with, this is not true. All topics appear! I went through last $$$3$$$ Div2 contests I coordinated. Among them:

1372E - Omkar and Last Floor and 1363F - Rotating Substrings are DP.

1364D - Ehab's Last Corollary, 1363C - Game On Leaves and 1363E - Tree Shuffling are graph problems.

1363D - Guess The Maximums is binary search problem.

However, it's somewhat true that easier problems are more often not related to these concepts. From my perspective, the reason for this is similar to the reason I provided in argument above: it's impossible hard to create an interesting DP/Binary Search/Graph problem which could fit positions D2A-D2C. Just because that concepts themselves are already quite challenging.

And I don't want to accept standard problems on DP/Binary Search/Graphs just to make the set more diverse or because you want it, and won't do so, I think.

3. While I understand that many people really like these topics and want them to appear as early problems, I believe that a lot of this feedback is coming from participants who learned some new algorithms/techniques and are sad when they don't become red they don't see these problems in contests.

Well, from my perspective, CP isn't about knowing algorithms, it's more about solving problems. Algorithms are tools. Knowing many algorithms means that you have a lot of tools, but if you don't know how to apply them, this won't help. That's why you should learn how to solve problems, not just learn algorithms.

4. Some people think that contests by me/coordinated by me aren't diverse enough, and contain too many constructive problems.

And well, I agree with this. I also believe that having too many constructive problems is not a good thing for a contest. From this perspective, Codeforces Global Round 9 wasn't very good. I also believe that the problemsets should be more diverse. However, when choosing between having less diverse problemset and accepting fairly standard problem, I will always prefer first.

Still, this is a valid objection. I will try to make problemsets more diverse :)

5. Some people think that I just won't accept Data Structure/Flow/Some string structures/Anything except ad hoc.

This is a very wrong point of view. I will accept problems in which idea is interesting enough. The problem is: it's much harder to create a problem on these topics which would at the same time be interesting than creating a good ad hoc problem. It seems that CP has evolved significantly in recent few years, and some things which weren't standard $$$4$$$ years ago, are very standard now. So yes, the reason why good nonstandard problems on these topics appear less now, is that there aren't many of them in proposals! However, still, expect to see some problems on these topics in future contests :D

6. While I understand people who say that it's sad when algorithms don't appear in contests, I don't think I understand people who get joy from struggling with implementing some problems. I am not against problems with quite long implementation, as long as implementation difficulty is smaller than the thinking difficulty. My opinion is best expressed here:

7. I would like to thank:

• People who provide objective criticism
• People who support my position
• MikeMirzayanov for great systems Codeforces and Polygon