chenjb's blog

By chenjb, 4 weeks ago, In English

UPD: We plan to host the 2024 Universal Cup Summer Summits in Cancún, Mexico. The event has been scheduled from June 19 to June 23. The detailed schedule, materials, and list of the invited teams will be announced in the future. The 2nd Universal Cup Semifinals will be held on June 23, 2024. The contest will start at 17:00 (UTC +8) and end at 22:00 (UTC +8). Please note that there will be no extra time windows on the semifinals contest — all the teams must start in the only official time window. You may check the event time on your local timezone here: Link. The onsite participants will participate in the semifinals on June 22nd (one day before the online participants)

Hello everyone, we are happy to announce the 2nd Universal Cup Semifinal and the 2024 Universal Cup Summer Summit.

In Season 2, thanks to everyone's support and efforts from our staff, there was a lot of progress compared to Season 1. We have over 3000 teams registered and so far we have scheduled over 30 stages in this season. We also managed to implement a registration webpage and host all kinds of contests on our platform, including the run-twice contest, the prime contest and the challenge contest. We also reached many agreements with Huawei about future cooperation, including the most exciting part: the onsite final. (Cooperation between Universal Cup and Huawei)

In the 2024 ICPC Latin American Championship, Universal Cup was invited to run the Huawei Challenge as a major part of the event. Our co-president Jingbang also gave a brief introduction of Universal Cup during the event to all the participants and coaches.

We still have more things coming! We have just finalized the rules for selecting the 2nd Universal Cup Final teams. The 2nd Universal Cup Semifinals will take place online, in order to select teams for the Final Contest. The contest is scheduled on one of the last two weekends of June (June 23 or 30). In addition, we have decided to host a special event, the 2024 Universal Cup Summer Summit in June. Supported by Huawei, we plan on inviting 10 teams to the wonderful city of Cancun, Mexico. The event will last around 5 days, including an onsite competition using the semi-final contest, a city tour, and some other activities. All fees will be covered by us. The exact schedule will be announced soon.

We want to express our gratitude again to everyone, especially problem-setters who have shared their wonderful contests with us. We are also planning to design souvenirs and prizes which will go to our contributors and participants, so stay tuned!

Here are the rules for the semifinal and the summer summit.

Details

Universal Cup

2024.3.19

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By chenjb, history, 6 months ago, In English

After a few days of waiting, ICPC finally sent out an announcement concerning the recent situation in Middle East:

ICPC Email Content

In all, unfortunately, after Covid, the WF22/23 Finalists have to wait for another few months to compete. Let's discuss this in this post.

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By chenjb, history, 13 months ago, In English

Hello Codeforces! The 9th Stage of the 1st Universal Cup is coming. It will be held from Mar 25th to 26th.

The contest is based on an official ICPC Asia East-Continent regional contest. It has been used in the 2018 ICPC Asia Qingdao Regional Programming Contest, which was prepared by the SUA Programming Contest Problem Setter Team.

Problem setters: zimpha, sfiction, J.T.J.L., shb123, TsReaper, reku, fengsuiyan, ZhouYuChen, MudCoal, NeverLand.Dai.

Testers: chenjb, oipotato, Subconscious, lsmll, jiangshibiao, lzw4896s.

As usual, we have three time windows for participating. You can participate in the contest in the following three time windows:

  • Mar 25th 13:00 — 18:00 (UTC +8)
  • Mar 25th 19:00 — 24:00 (UTC +8)
  • Mar 26th 02:00 — 07:00 (UTC +8)

Please note that you can see two scoreboards in DOMjudge. The 'Local Scoreboard' shows the standings ONLY IN THE CURRENT TIME WINDOW. And the 'Combined Scoreboard' shows all participants, including the onsite participants, and the cup participants in the previous time windows.

Contest link: https://domjudge.qoj.ac/

Universal Cup Scoreboard: https://qoj.ac/ucup/scoreboard

UPD:

Now the contest has been uploaded to Gym: The 2018 ICPC Asia Qingdao Regional Programming Contest (The 1st Universal Cup, Stage 9: Qingdao)

Editorial Wiki: Chinese, English

About Universal Cup:

Universal Cup is a non-profit organization dedicated to providing trainings for competitive programming teams. Up to now, there are more than 500 teams from all over the world registering for Universal Cup.

A more detailed introduction: https://mirror.codeforces.com/blog/entry/111672

Register a new team: https://ucup.ac/register (the registration request will be processed before each stage)

Results of the past stages: https://ucup.ac/results

Terms: https://ucup.ac/terms

Ratings: https://ucup.ac/rating

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By chenjb, history, 21 month(s) ago, In English

Hello! I'm happy to announce XXII Open Cup: Grand Prix of ByteDance, which will be held on July 24th, 2022.

This contest is first used in ByteDance Programming Camp 2022 on July 15th as the Final contest. It is organized by me, and prepared by 14 experienced problem setters who set at least 22 EC ICPC contests and 10 CCPC contests over the past 7 years. We believe this contest is both challenging, fun and might even be educational for teams.

Here representing the whole contest setting committee, I want to express our gratefulness to ByteDance for organizing this great camp and sponsor this contest, Oleg Hristenko for providing technical support, and our testing team (mayaohua2003, gtrhetr, 142857) and our coaches (jqdai0815, jiry_2, Claris, Gromah) for their help.

Problem Setters: quailty, Claris, Gromah, nothing100, Tommyr7, UESTC_Nocturne, shb123, oipotato, xyz2606, chenjb, Orenji.Sora, TsReaper, jiangshibiao, skywalkert.

Contest Link (Div.1): Yandex

UPD:

The contest is over now and please feel free to discuss.

Official Editorial: Dropbox

The contest will be uploaded onto Gym in the future.

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By chenjb, history, 2 years ago, In English

Happy New year, Codeforces.

I had this idea for about a month. I heard problem setters complaining about some people used their coach mode authority to enlarge some problems' TL in the Gym just for letting their submissions passed. What's worse, these guys even forgot to change it back, which causes some troubles for participants afterwards.

Moreover, I also have similar experience. Back in 2020, I did SWERC2019 with my friends. Then after a few days, I returned and found that my competition record disappeared from the scoreboard. Someone must press the 'to practice' or 'devirtualize' button. If you press those buttons, the website will ask you if you confirm your action (which is not reversible). Therefore, I pretty sure there is someone who just don't want to see my partipation record on the scoreboard for some reasons that I could never realize.

Just in case some of you don't know (maybe hasn't discovered yet) what the coach mode can do, here are some authority that you can do with a coach mode:

  1. Read any submission and data (this is well-known);
  2. Edit TL, ML for any problem;
  3. Add, delete problems of any contest
  4. Add, delete teams' participation record, ghosts from the scoreboard
  5. Rejudge, skip, reject any submission

The Codeforces community is getting larger, and therefore it is getting relatively easier to achieve Master rating (>=2100), which is what I know about getting a coach mode authority (maybe slightly different but generally it is i guess). I think it is about time to restrict the coach mode authority tighter before anything worse happens.

The simplest way is, of course, to limit it by increasing the rating bound(maybe >=2400). But it might be too mean for the community. But at least, I feel it will be more appropiate to let the contest/problem setter has more rights to modify the contest by himself. And I feel it is OK to let the normal coach mode only have the authority to read submissions and data instead of everything. I haven't got time to think about more possible options and I hope we can have some discussions in the comment.

I don't know whether Mike will see this blog so I think I should @MikeMirzayanov here. And I still want to express my gratefulness for building and maintaining such a useful and convenient platform (including Polygon) for all CP participants and problem setters.

UPD1: Some comments say that if you are purple and have done a few contests, you also will get a coach mode authority.

UPD2: Just check another example, in 2021-2022 ICPC, NERC, Southern and Volga Russian Regional Contest, you will see that Team Longest SubRoutine also got removed from the scoreboard for no reason (Confirmed by the team that it is not by their hands). This is truly a disregard to the team's effort and may ruin their training log.

Actually I am not very happy about not seeing any officials including Mike himself to respond this. I feel this is a serious issue at least as important as finding and solving potential hardware issues.

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By chenjb, history, 2 years ago, In English

Hello! I'm happy to announce XXII Open Cup: Grand Prix of Nanjing, which will be held on Dec 12th, 2021.

This contest is mainly prepared by SUA Programming Contest Problem Setter Team, which has already been used as the 2021 ICPC Asia Nanjing Regional Contest. There are around 700 teams participating in the Regional.

This is the fourth Nanjing Regional and the third Grand Prix of Nanjing in Open Cup, I feel very grateful and wish everyone enjoy this contest.

We also have an anonymous author this year. He provides a very interesting problem to this contest.

Authors: chenjb, TsReaper, jiangshibiao, shb123, quailty, Subconscious, oipotato

Testers: KAN, Um_nik, Merkurev, TLE, antontrygubO_o, Rewinding, J.T.J.L., tun, sfiction, cxt, pb0207, Eden_CY, Suika_predator, lwn_16, lxlxl, xpchf, liyang21, AkaiLemon, nothing100, UESTC_Nocturne, Orenji.Sora, Gromah, smax, arvindr9, RandomKami

Contest link: https://official.contest.yandex.ru/opencupXXII/contest/33444/enter (Only visible for users with OpenCup login)

Open Cup Scoreboard: http://opentrains.snarknews.info/~ejudge/res/res10559

Regional Scoreboard: https://board.xcpcio.com/icpc/46th/nanjing

UPD: The contest is in the gym now.

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By chenjb, history, 2 years ago, In English

Hello! I'm happy to announce XXII Open Cup: Grand Prix of EDG, which will be held on Nov 14th, 2021.

This contest is mainly prepared by Zhejiang University, which has already been used as the 2021 CCPC Guilin Contest.

On the same day of the 2021 CCPC Guilin Contest, Team Edward Gaming (EDG) from League of Legends Pro League (LPL, China) won the Champion of the 2021 League of Legends World Championship held in Reykjavík. They are also the only LPL team entering the semi-finals while the rest of three teams all coming from League of Legends Champions Korea (LCK, Korea), including the champion from last year. Almost nobody would bet on their winning, but they made it and reclaim the glory for LPL after 2 years.

Team EDG has been doubted for a long time because their performance in the World Championship is usually very struggled and disappointing. However, they never give up their dream. Their brave heart and the strong will push them go forward. Now they make the history. Their spirit moves everyone and their legend lasts forever.

As well as contestants, problem setters are also deeply touched by their victory. Their spirit inspires us. In competitive programming, it is the same spirit that drives us improve ourselves, challenging problems and enjoying every contest.

Therefore, we decide to call this contest as the GP of EDG.

Coordinators: oipotato, Claris

Authors: oipotato, Claris, chenjb, lxlxl, Subconscious, pb0207, Sugar_fan, shb123, lwn_16, quailty, Suika_predator.

Testers: SSerxhs, Eden_CY, cxt, nothing100, UESTC_Nocturne, Orenji.Sora, Onozuka, Maniac_Wallnut, Randias, qiqi20021026, DeepinC, szb, LOLtxdy, Sdchr, chenyanbo, Tommyr7. Thank you!

Contest link: https://official.contest.yandex.ru/opencupXXII/contest/31241/enter (Only visible for users with OpenCup login)

Gym link: https://mirror.codeforces.com/gym/103409

I will publish this contest to gym and please feel free to discuss afterwards.

UPD1: The link posted.

UPD2: The contest has been uploaded to Gym.

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By chenjb, history, 3 years ago, In English

The ICPC headquarter sents an e-mail to update the status of WF2020:

Content

In summary, contestants of WF2020 won't need to be together. Each individual can choose to be on-site or remote separately. Moreover, it seems we can use our own computers, which means this is still the same as the 3-machine mode as NERC last year.

Although I am not the contestant of WF2020 (yet another sad and angry story), I still think this kind of WF mode is not fair. 3-machine is totally different kind of competition as the normal ICPC contest. Moreover, I don't think ICPC has the anti-cheating or monitoring technology system that is powerful enough in such important event.

From what I know in 2020-2021 season, only Chinese Regionals did use some comprehensive anti-cheating system. What if some contestants share their account to others, like gathering 10-20 people working on the contest. Does ICPC's technology is strong enough to prevent such things happen? It is the responsibility of the host and ICPC to make sure the competition is technically fair.

I know these years are special. The global pandemic strongly affects everything. But I still think any event should be hosted properly. Otherwise, the best choice might be postponed or cancelled.

What's everybody's opinion on this? Especially for those WF2020 contestants.

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By chenjb, history, 3 years ago, In English

Hello, Codeforces!

The 2020 ICPC Asia Macau Regional Contest has ended on May 29th.

The problems for this contest were prepared by Zhejiang University. We are glad to announce that we have published the contest, The 2020 ICPC Asia Macau Regional Contest in Codeforces::Gym for you to practice. Feel free to start virtual participation or to solve the problems individually. For virtual participation, the contest is 5 hours in length and follows usual ICPC rules. Team participation is recommended, but it is also possible to participate individually. The ghosts of the onsite participants are available, you may take advantage of it.

My thanks go to:

University of Macau

Problem authors: shb123, Sugar_fan, Claris, chenjb, Subconscious, lxlxl, quailty

Testers: jqdai0815, cxt, mengbierr, Rewritetxdy, chenyanbo, Orenji.Sora, Sdchr, pb0207, niike0goood

MikeMirzayanov for the Codeforces platform and the Polygon system where we prepared the problems.

The contest link is The 2020 ICPC Asia Macau Regional Contest

We have prepared an English editorial. Hope you enjoy the problems and feel free to discuss them in the comments.

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By chenjb, history, 3 years ago, In English

Hello! The 18th Zhejiang Provincial Collegiate Programming Contest has been uploaded to the Gym.

The link is The 18th Zhejiang Provincial Collegiate Programming Contest .

This contest also serves as Contest 3, Div.A in this year's Moscow Pre-Finals Workshop 2021, so we also prepare an English tutorial. Note that the contest version in Gym is different from the original version used in ZJCPC. We enlarge the data constraint in H and K to prevent some unintended solutions passing.

Authors: oipotato, Claris, chenjb, Subconscious, shb123, Suika_predator, lxlxl, lwn_16

Testers: Tommyr7, applese, Timsei, quailty, Sugar_fan, SSerxhs, cxt, mengbierr, pb0207, l1ll5, Eden_CY, Jak033021, KanaD ,

Official Scoreboard: Official Scoreboard

Pre-Finals Link: Pre-Finals Link

Tutorial: Tutorial in Dropbox

If anyone can help upload these scoreboards to Gym, we will be very grateful.

Please feel free to discuss problems in comments and hope you enjoy this contest.

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By chenjb, history, 3 years ago, In English

Hello! Happy New Year! I'm happy to announce XXI Open Cup: Grand Prix of Nanjing, which will be held on Jan 10th, 2021.

This contest is mainly prepared by SUA Programming Contest Problem Setter Team, which has already been served as the 2020 ICPC Asia Nanjing Regional Contest.

Authors: chenjb, zimpha, shb123, TsReaper, oipotato, jiangshibiao, MudCoal

Testers: 300iq, Um_nik, Merkurev, KAN, jqdai0815, Suika_predator, lwn_16, lxlxl, Sugar_fan, liguanglin, lyk248289469. Thank you!

Contest link: http://official.contest.yandex.ru/opencupXXI/contest/24046/enter (Only visible for users with OpenCup login)

I will publish this contest to gym and please feel free to discuss afterwards.

UPD: An editorial written in Chinese Zhihu and I will make an english version later (hopefully).

UPD2: Now it is in the gym.

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By chenjb, history, 3 years ago, In English

I only update all CCPC contests information and all ICPC contests found in Gym for the first publish so far.

In recent years, there are two main programming competitions held in China: China Collegiate Programming Contest (CCPC) and International Collegiate Programming Contest (ICPC). These contests are prepared by universities or groups in China and some of them are of very high quality.

Before I was retired, I find it quite hard and annoying to find these contests since they are uploaded in many different websites and some of them might come with wrong data. What's worse, some contests are not allowed to participate virtually or even not been published to any website at all. So I wanna make an aggregation here to help those who are interested in these contests.

I will mainly focus on contests from 2014 — 2020 and I will update it when new contests are published. I hope authors could make comments under this blog to inform me about it.

1.China Collegiate Programming Contest (CCPC)

2020: (4 sites and 1 Finals)

Qinhuangdao by Tsinghua U: 2020 China Collegiate Programming Contest Qinhuangdao Site

Weihai (XXI OpenCup, Gp of Weihai) by Nanjing U: 2020 China Collegiate Programming Contest, Weihai Site

Mianyang by UESTC: 2020 China Collegiate Programming Contest - Mianyang Site

Changchun by Shanghai JTU: 2020 China Collegiate Programming Contest Changchun Onsite

Finals: Expected in 2021.

2019: (3 sites and 1 Finals)

Qinhuangdao by Fudan U: 2019 China Collegiate Programming Contest Qinhuangdao Onsite

Harbin by Zhejiang U: The 2019 China Collegiate Programming Contest Harbin Site

Xiamen by SYSU: Already used in a Moscow workshop camp, not published.

Finals (XIX OpenCup, Gp of Beijing) by Google: 2019 China Collegiate Programming Contest Final (CCPC-Final 2019)

2018: (3 sites and 1 Finals)

Qinhuangdao by Tsinghua U: Not published.

Jilin by Shanghai JTU: Vjudge Replay

Guilin by UESTC: 2018 China Collegiate Programming Contest - Guilin Site

Finals by Google: 2018 China Collegiate Programming Contest Final (CCPC-Final 2018)

2017: (3 sites and 1 Finals)

Qinhuangdao by Zhejiang U: ZOJ

Harbin by SYSU: Vjudge Replay

Hangzhou by Fudan U: Vjudge Replay

Finals by Google: Vjudge Replay

2016: (3 sites and 1 Finals)

Hefei by Tsinghua U: Vjudge Replay

Hangzhou by UESTC: Vjudge Replay

Changchun by Shanghai JTU: Vjudge Replay

Finals by Google: Vjudge Replay

2015: (1 Finals)

Finals by Google: Vjudge Replay

2.International Collegiate Programming Contest (ICPC)

2019:

2019 ICPC Asia-East Continent Final

2019-2020 ICPC Asia Hong Kong Regional Contest

2018:

2018-2019 ACM-ICPC, Asia East Continent Finals

2018-2019 ACM-ICPC, Asia Jiaozuo Regional Contest

2018-2019 ACM-ICPC, Asia Xuzhou Regional Contest

2018-2019 ACM-ICPC, Asia Nanjing Regional Contest

2018-2019 ACM-ICPC, Asia Shenyang Regional Contest

2017:

2017-2018 ACM-ICPC Asia East Continent League Final (ECL-Final 2017)

2016:

2016-2017 ACM-ICPC CHINA-Final

2014:

2014-2015 ACM-ICPC, Asia Mudanjiang Regional Contest

2014-2015 ACM-ICPC, Asia Xian Regional Contest

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By chenjb, history, 4 years ago, In English

Hello! I'm happy to announce XX Open Cup: Grand Prix of Nanjing, which will be held on May 3rd, 2020.

This contest is mainly prepared by gisp_zjz and me, which has already been used in Moscow Pre-Finals Workshop 2020 Day 5 on April 29th, 2020.

As you can see on the top of the statement, this contest is also been called Legilimens+Coffee Chicken Contest. Team Coffee Chicken from Nanjing University will participate in World Finals 2020 and we wish them best luck in Moscow. Team Legilimens is from Zhejiang University, which is my team in the past 3 years. Although we didn't get advanced to World Finals 2020 and this is the end of our journey, we have experienced a lot of happy and unforgettable moments. Therefore, please allow me to express my gratefulness to my teammates Subconscious and oipotato. And may the friendship between Nanjing University and Zhejiang University last forever.

Authors of this contest come from Competitive Programming Team members from both Zhejiang University and Nanjing University, including gisp_zjz, AceSrc, zyb, Roundgod, calabash_boy, sy_chen, chenjb, Subconscious, oipotato, Sugar_fan, etc.

Testers: mayaohua2003, gtrhetr, xiaowuc1. Thank you!

Contest link: http://official.contest.yandex.ru/opencupXX/contest/18242/enter (Only visible for users with OpenCup login)

I will post the editorial after the contest. We are looking forward to your participation!

UPD: Now it is over. Please feel free to discuss solutions and this is the Editorial Sketch.

UPD2: Now it is in the gym.

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By chenjb, history, 4 years ago, In English

Gp of Zhejiang is over...Let's discuss solutions. How to solve C?

Is there an editorial? jqdai0815

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By chenjb, history, 5 years ago, In English

ZOJ Monthly, January 2019 will be held on Saturday (time). The main problem setters are chenjb and Claris.

Contest Link

It will last for 5 hours and have 8-9 problems in total. Since there is no rating system(Thanks to MudCoal, we may have one in the future) in our Zhejiang University Online Judge, it will be unrated. And I guess the difficulty is as a normal Educational Contest in Codeforces.

All problem ideas come from members of Zhejiang University Programming Contest Setting Team and most of them have already been used in the Internal Member-Selection Contests in ZJU held in July, 2018. They have been carefully selected, modified, tested by our problem setters and rearranged into this Monthly contest eventually.

Special thanks to Claris for helping me testing problems, modifying the content and some other matters. He even gives better and stronger solutions to some problems, which make them more interesting and challenging. I am very grateful.

Also thank TsReaper and shb123 for the help and zimpha, lyk248289469, Sugar_fan, HbFS-, johann_wang, Onlynagesha, zhhhplus, etc for their ideas.

There have been less ZOJ Monthly Contests these years. Therefore, we cherish every chance and wish to make every Monthly contest as good as possible. I really hope all of you can enjoy this contest. Can't wait to see you guys on Saturday!

UPD: The contest will begin in less than 9 hours and there will be 9 problems in total. If you have any question about the contest, please make comments under this blog. And please not to discuss about the solution until the contest ends.

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