ranks between 31 and 500, inclusive. The prizes for the 6-round series in 2019
: - In each, среди участников с 31-го по 500-е место. Призы в серии из 6 раундов в 2019
году: - За каждый, 1. [user:Radewoosh,2019-10-16] 2. [user:Petr,2019-10-16] 3. [user:300iq,2019
-10-16] 4, The prizes for the 6-round series in 2019:, [user:KAN,2019-10-16], [user:Endagorion,2019-10-16], [user:arsijo,2019-10-16],
[user:Rox,2019-10-16, Призы в серии из 6 раундов в 2019 году:
→ Обратите внимание
→ Трансляции
→ Лидеры (рейтинг)
| № | Пользователь | Рейтинг |
|---|---|---|
| 1 | jiangly | 3810 |
| 2 | Benq | 3676 |
| 3 | Kevin114514 | 3655 |
| 4 | maroonrk | 3463 |
| 5 | strapple | 3447 |
| 6 | Um_nik | 3387 |
| 7 | heuristica | 3322 |
| 8 | turmax | 3317 |
| 9 | tourist | 3307 |
| 10 | jiangbowen | 3291 |
| Страны | Города | Организации | Всё → |
→ Лидеры (вклад)
| № | Пользователь | Вклад |
|---|---|---|
| 1 | Qingyu | 156 |
| 2 | nik_exists | 150 |
| 2 | maspy | 150 |
| 4 | Um_nik | 141 |
| 5 | Errichto | 139 |
| 6 | adamant | 137 |
| 7 | AmShZ | 135 |
| 8 | BledDest | 132 |
| 9 | maroonrk | 131 |
| 10 | qwexd | 129 |
→ Найти пользователя
→ Прямой эфир
Можно ввести несколько слов — все они попадут в требования к поиску. Кроме того, осуществляется поиск по словоформам и, если повезет, по синонимам. Поддерживается поиск по названию, автору и специальный синтаксис запросов. Примеры:
305— ищет все посты, содержащие 305, найдет посты про Раунд 305andrew stankevich contests— можно писать сразу много слов, будут искаться всеuser:mikemirzayanov title:сазанка— ищет все посты в названии со словом "сазанка" авторства MikeMirzayanov"vk cup"— можно использовать кавычку, чтобы искать точные совпаденияtitle:educational— искать в названии
Результаты
1.
Codeforces Global Round 5 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Hey!
On [contest_time:1237] we will host [contest:1237].
It is the fifth round of a new series of [Codeforces Global Rounds](https://codeforces.me/blog/entry/65002) supported by XTX Markets. The rounds are open for everybody, the rating will be updated for everybody.
The round will last for 2 hours 30 minutes, 8 problems are waiting for you, and one of them will be proposed in two versions.
Scoring distribution: **500 — 750 — (750 + 750) — 2000 — 2500 — 3000 — 3750 — 4000**
The prizes for this round:
- 30 best participants get a t-shirt.
- 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.
The prizes for the 6-round series in 2019:
- In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT).
- The fi...
2.
About the Failed Round 591/Technocup 2020 — Elimination Round 1 Hi Codeforces!
Unfortunately, ill-wishers thwarted the round by making DDOS on our infrastructure. Neither the coordinator nor the writers of the round are subjects to blame for the failure. Please do not downvote the announcement of the round. I think that this situation is an additional reason to support the writers. They worked hard and prepared good problems!
Apparently, such an attack should be regarded as a symptom of the fact that Codeforces outgrew the youth phase and entered serious adult life. Of course, we will respond with adequate measures to protect ourselves from such incidents. Fortunately, for almost 10 years of work, a large community has formed around those who care about Codeforces. We are not worried about possible additional expenses or efforts. We can do this. The rounds must go on.
— [user:MikeMirzayanov,2019-10-06]
**UPD 1:** All three of today's rounds will be unrated.
**UPD 2:** Hooray! Today we've survived another DDOS attack. The round ...
— [user:MikeMirzayanov,2019-10-06]
3.
Hello 2019 Hello coders! I hope that you are enjoying the New Year as much as me. To make its beginning even greater, Codeforces is going to host a contest and I will be an author of all tasks. Hello 2019 will take place on [Friday](https://www.timeanddate.com/worldclock/fixedtime.html?day=4&month=1&year=2019&hour=17&min=35&sec=0&p1=166).
Using the opportunity, I want to thank to:
- [user:lewin,2019-01-02] and [user:mnbvmar,2019-01-02] for testing the round.
- [user:mnbvmar,2019-01-02] for indescribably helpful discussions about problems.
- [user:_kun_,2019-01-02] and [user:KAN,2019-01-02] for round coordination and help with preparation.
- [user:MikeMirzayanov,2019-01-02] for such great platforms (you know which ones :P).
The round will consist of 8 problems and you will be given <s>two and a half</s> three hours to solve them. Yes, the round will be **rated**.
There will be no interactive problems, but if you want you can read [this](https://codeforces.me/blog/entry/45307) docum...
Hello 2019, greater, Codeforces is going to host a contest and I will be an author of all
tasks. Hello2019 will, - A: [user:Errichto,2019-01-05] - B: [user:dorijanlendvaj,2019-01-05] - C:
[user:Um_nik,2019-01, - [user:lewin,2019-01-02] and [user:mnbvmar,2019-01-02] for testing the round.
- [user:mnbvmar, 1. [user:V--o_o--V,2019-01-05] 2. [user:ecnerwala,2019-01-05] 3. [user:tourist,
2019-01-05] 4
Анонс Hello 2019
4.
Goodbye 2019. Hello 2020! <img src="/predownloaded/85/58/8558df7ac8a1c33d501ea8fd9b18dd3d95886b90.png" style="width:290px; float:right; margin: 0 1.5em 1.5em 1.5em"/>
I am happy to wish you a Happy New Year! I wish you a great, bright, interesting New Year! Just believe that it can become so: difficulties will be left behind, and ahead of you will be a joy of victories and discoveries.
I wish all of us new interesting problems, records and achievements! Set new goals and be sure to try to achieve them! And do not go far, we will try to make your 2020 year more fun!
I thank with all my heart for the contribution to the community of coordinators, problem writers, testers, and those who wrote interesting posts and comments. Many thanks to the sponsors, partners and customers: you help the community not to stand still, give the opportunity to hold interesting events. Thanks to all visitors to the website and just not indifferent.
See you in the new year!
— [user:MikeMirzayanov,2019-12-31]
Goodbye 2019. Hello 2020!, and just not indifferent. See you in the new year! — [user:MikeMirzayanov,2019
-12-31], — [user:MikeMirzayanov,2019-12-31]
5.
Good Bye 2019 Снова привет, Codeforces!
Мы ради пригласить вас на <s>Mathforces</s> <s>Thinkforces</s> [Good Bye 2019](https://codeforces.me/contests/1270), который пройдет [contest_time:1270].
Немного информации о раунде:
<ul>
<li>Рейтинговый для всех участников!</li>
<li>3 часа!</li>
<li> <strong> Никаких подзадач! </strong> </li>
<li> В раунде будет <strong> интерактивная задача </strong>. Вы можете ознакомиться с руководством по интерактивным задачам [здесь](https://codeforces.me/blog/entry/45307)</li>
<li> Разбор будет опубликован сразу после окончания системного тестирования </li>
</ul>
Все задачи в этом раунде были приготовлены нами, [user:antontrygubO_o,2019-12-28] и [user:kefaa2,2019-12-28]. Мы долго работали над эти раундом и постарались сделать все задачи очень интересными. Надеемся, вам понравится раунд!
Мы бы хотели поблагодарить:
<ul>
<li> [user:arsijo,2019-12-24] за координацию раунда </li>
<li> [user:GandalfTheGrey,2019-12-24] за идею решени...
Good Bye 2019,
* [user:Radewoosh,2019-12-29]
* [user:Um_nik,2019-12-29] ,
* [user:arsijo,2019-12-24] for coordination of the round ,
* [user:arsijo,2019-12-24] за координацию раунда
* [user:GandalfTheGrey,2019, Bye 2019](https://codeforces.me/contests/1270), which will take place on
[contest_time:1270, Bye 2019](https://codeforces.me/contests/1270), который пройдет
[contest_time:1270]. Немного, ://codeforces.com/blog/entry/72557) between [user:tourist,2019-12-28] and
[user:Um_nik,2019-12-28], which, ://codeforces.com/blog/entry/72557) между [user:tourist,2019-12-28] и
[user:Um_nik,2019-12-28], которое, All problems in this round were prepared by us, [user:antontrygubO_o,2019
-12-28] and, Все задачи в этом раунде были приготовлены нами, [user:antontrygubO_o,2019
-12-28] и
Анонс Good Bye 2019
6.
Goodbye A2 Online Judge :( I'm sadly announcing that [a2oj.com](https://a2oj.com/) ([A2 Online Judge](https://www.facebook.com/A2OnlineJudge/)) will be retiring by end of 2019, I'll shut it down at midnight on New Year's Eve. It was something I took care of for about 10 years.
I'm really sorry, but I prefer not to explain my reasons, so please don't ask me why I'm doing this, it was hard enough for me to make this decision, and also please don't try to convince me to change my mind.
I'd like to say thank you to everyone who used it, and please accept my sincere apologies for shutting it down.
If you have something good to say about A2OJ (how you used it or how it helped you in any way), I'd love to read that, please send it to the following email (or in a comment here): [email protected]
Also please feel free to take a copy of any data you can access, and if you need some data in a specific format, please send your request to the following email: [email protected] (if the data isn't public, make sure to send f...
/A2OnlineJudge/)) will be retiring by end of 2019, I'll shut it down at
midnight on New Year's Eve
7.
Codeforces Round #589 (Div. 2) **다시 만나서 반가워요, 코드포스!** (Nice to see you again, Codeforces!)
I'm again happy to introduce you to [Codeforces Round #589 (Div. 2)](https://codeforces.me/contests/1228). Please look at following information for details:
- This contest will take place on [contest_time:1228].
- The round will be **rated for all Division 2 participants**.
- There are **6 problems** and you will have **2 hours** to solve them. Score distribution will be announced later.
The listed handles below are contributors. Thank you for all who listed!
- **Main author**: ~McDic,2019-09-26 — I made and prepared all problems.
- **Coordinator**: ~arsijo,2019-09-26 — He is my coordinator again.
- **Early phase testers**: ~dorijanlendvaj,2019-09-26 ~tfg,2019-09-26 ~Lawali,2019-09-26 — They are early phase testers. They mostly focused on test data.
- **Late phase testers**: ~_Kuroni_,2019-09-26 ~imbr92,2019-09-26 ~Redux,2019-09-26 ~Dr_Park,2019-09-26 ~Mahotsukai,2019-09-26 ~TOPWINDFLOWER,20...
contributors. Thank you for all who listed! - **Main author**: ~McDic,2019
-09-26 — I made and, - **Main author**: ~McDic,2019-09-26 — I made and prepared all problems. -
**Coordinator, 1. ~PositionZero,2019-09-29 2. ~supy_2,2019-09-29 3. ~hitman623,2019-09-29 4.
~lzqaq,2019-09-29
8.
Goodbye 2021. Hello 2022! <img src="/predownloaded/f4/1f/f41ff0beb745fb2f84a55d9f2cc451273efc6267.jpg" style="width:300px; float:right; margin: 0 1em 1em 1em"/>
Hello Codeforces!
Oh yes, 2021 ends! I recently realized that 2022 is pronounced like "2020 too". Not that. I want a completely different year!
Anyway, we did a nice job this year. I hope we have pleased you with interesting problems.
Thanks to the round coordinators and writers! You make our community richer. Please make us happy in 2022!
I wish you all interesting tasks and brilliant solutions! I wish you error-free code and wish us only rated rounds :-)
Hello, 2022!
And we have traditional gifts!
#### <img src="https://assets.codeforces.com/images/wand.png"/> Change Handle Feature
Hurry! Only until the 10th of January, you can change your handle (<b>but only once</b>)! Note that it will be possible to roll back the changes or change the handle again only _after a year_. Be careful what you wish for.
You can change your han...
180 days, this period should be in 2019 or earlier. The inactive participant
can't have posted, , this period should be in 2019 or earlier. The inactive participant can't have
posted comments
9.
Codeforces Raif Round 1 [Div. 1 + Div. 2] Hello, Codeforces!
Welcome to the [contest:1428] supported by Raiffeisenbank, that will start on [contest_time:1428]. **It will be a combined rated round for both divisions. Note that the start time is unusual.**
All problems were authored and prepared by [user:bensonlzl,2020-10-15], [user:oolimry,2020-10-15], [user:errorgorn,2020-10-15], [user:dvdg6566,2020-10-15], [user:shenxy13,2020-10-15].
[user:Ari,2020-10-15] gato to:
- [user:isaf27,2019-05-10] and [user:KAN,2020-10-15] for round coordination and help with preparation
- [user:zhangguangxuan99,2020-10-15] for being epic IOI trainer <3
- Our army of testers: [user:Ari,2020-10-15], [user:KAN,2020-10-15], [user:Monogon,2020-10-15], [user:Prabowo,2020-10-15], [user:SYY,2020-10-15], [user:SleepyShashwat,2020-10-15], [user:TeaTime,2020-10-15], [user:Tlatoani,2020-10-15], [user:_rs_,2020-10-15], [user:agul,2020-10-15], [user:cstuart,2020-10-15], [user:dantoh,2020-10-15], [user:jhkoh,2020-10-15], [user:kai824,2020-10-15]...
замечания. - [user:MikeMirzayanov,2019-05-10] за замечательные системы
Codeforces и Polygon, - [user:MikeMirzayanov,2019-05-10] for great systems Codeforces and Polygon., - [user:MikeMirzayanov,2019-05-10] за замечательные системы Codeforces и
Polygon.
10.
Corruption, Cheating at ICPC Yinchuan This blog is about Corruption and Cheating at ICPC YinchuanRegional. ICPC Yinchuan Regional is one of the ICPC regional contests for students competing in the geographic area of Asia East Continent.
I. Background: General Info
------------------
Ningxia Institute of Science of Technology, or NXIST is a higher education institute in China. Since 2019, NXIST has held two regional contests. The and both were considered by many participants as jokes, yet until today participants are unaware of the NXIST's extent of evil.
Zhihu is a Chinese website similar to Quora, and I will refer to this website for information.
II. Background: Before 2021
------------------
Regional competitions in China consists of two stages: The online selection contest and the onsite regional contest. As there are many contestants in China, the online contest is considered serious and rules are usually strictly enforced, with entire universities where some participant cheats disqualified from attend...
NXIST is a higher education institute in China. Since 2019, NXIST has held two
regional contests, Yinchuan Regional Contest held by NXIST in 2019, NXIST used exactly the same
problems as the 2018, . Since 2019, NXIST has held two regional contests. The and both were
considered by many participants as
11.
Технокубок 2020 — Отборочный Раунд 1 (и открытые рейтинговые раунды Codeforces Round 591 Div.1, Div.2) Добрый день!
<p><a style="float:right;margin:0 0 1em 1em;" href="http://codeforces.me/technocup2020"><img src="http://assets.codeforces.com/images/technocup-narrow-logo.png"/></a>
В [contest_time:1223] состоится <a href="/contests/1223">Отборочный Раунд 1</a>
олимпиады для школьников <a href="http://codeforces.me/blog/entry/70187">Технокубок 2020</a>.
Раунд будет длиться два часа, участникам будут предложены 7 задач. По его результатам лучшие участники
(но не более 45% от общего числа участников раунда) будут приглашены на финальный этап в Москву.
Для регистрации на раунд и участия перейдите <a href="http://codeforces.me/contests/1223">по ссылке</a>.
Не забудьте заранее зарегистрироваться на раунд! Для опоздавших будет открыта дополнительная регистрация.
<p style="text-align:center">
<a style="font-size:20px;" href="http://codeforces.me/contests/1223">Зарегистрироваться на Отборочный Раунд 1 →</a>
<br/>
<small>Соревнование открыто для всех в виде отдельных ...
Авторы отборочного раунда — [user:BledDest,2019-10-06], [user:MikeMirzayanov,
2019-10-06
, contests! The Elimination Round authors are [user:BledDest,2019-10-06],
[user:MikeMirzayanov, ,2019-10-06], [user:MikeMirzayanov,2019-10-06], [user:Ne0n25,2019-10-06],
[user:PikMike,2019-10-06, The Elimination Round authors are [user:BledDest,2019-10-06],
[user:MikeMirzayanov,2019-10-06
12.
Codeforces: Итоги 2019 <a style="float:right; display: inline-block; margin:0 1em 1em 2em; max-width: 60%;" href="https://codeforces.me/10years"/>
<img style="max-width:100%" src="https://assets.codeforces.com/images/codeforces-10-years-300.png"/>
</a>
Привет, Codeforces!
Недавно платформе исполнилось <b>10 лет</b>. Мы принимаем ваши поздравления по ссылке <b><a href="https://codeforces.me/10years">https://codeforces.me/10years</a></b>. Пожалуйста, ознакомьтесь
с прогрессом в 2019-м году и <a href="https://codeforces.me/10years">поддержите краудфандинг-кампанию</a> по случаю юбилея. Ваше пожертвование станет вкладом в будущее Codeforces, поможет его развитию и работе. Нам нужны ресурсы,
чтобы продолжать проводить раунды, не останавливаться в разработке, внедрять нововведения и поддерживать существующую инфраструктуру.
В 2019-м году над задачами совместно с многочисленными авторами работали координаторы: [user:KAN,2020-02-06], [user:300iq,2020-02-06], [user:cdkrot,2020-02-06], [user:arsijo,20...
13.
Codeforces Round #580 
И снова привет, Codeforces!
Я рад пригласить вас на [Codeforces Round 580](https://codeforces.me/contests/1205,1206), который состоится в [contest_time:1205]. Раунд будет рейтинговым для обоих дивизионов.
Все задачи в этом раунде придуманы и подготовлены мной, [user:antontrygubO_o,2019-08-16]. Я постарался сделать их идейными и очень надеюсь, что они вам понравятся!
Спасибо [user:arsijo,2019-06-29] за отличное координирование раунда, [user:kefaa2,2019-06-29], [user:gepardo,2019-06-29], [user:danya.smelskiy,2019-08-16], [user:re_eVVorld,2019-08-16], [user:Xellos,2019-08-16], [user:GandalfTheGrey,2019-06-29], [user:prof.PVH,2019-08-16], [user:KAN,2019-08-16] за тестирование и ценные замечания, а также Михаилу [user:MikeMirzayanov,2019-06-29] Мирзаянову за отличные платформы Codeforces и Polygon.
В каждом дивизионе будет предложено 6 задач и 2 часа 10 минут на их решение. Как всегда, **настоятельно** рекомендую прочитать условия всех ...
prepared by me, [user:antontrygubO_o,2019-08-16]. I tried to make them
interesting and hope that you, подготовлены мной, [user:antontrygubO_o,2019-08-16]. Я постарался сделать их
идейными и очень надеюсь, что, **1.** [user:TLE,2019-08-18], **2.** [user:Um_nik,2019-08-18], **2.** [user:sucuk,2019-08-18], **3.** [user:mnbvmar,2019-08-18], **3.** [user:ujrepacul,2019-08-18], **4.** [user:Benq,2019-08-18], **4.** [user:zzffxx,2019-08-18], **5.** [user:CauchySheep,2019-08-18], **5.** [user:Illicit,2019-08-18], A lot of thanks to [user:arsijo,2019-06-29] for the excellent coordination of
the round, All problems in this round were created and prepared by me,
[user:antontrygubO_o,2019-08-16]. I, Все задачи в этом раунде придуманы и подготовлены мной, [user:antontrygubO_o,
2019-08-16]. Я, Спасибо [user:arsijo,2019-06-29] за отличное координирование раунда,
[user:kefaa2,2019-06-29
14.
A problem collection of ODE and differential technique ##A problem collection of ODE and differential technique
*This problem might be well-known in some countries, but how do other countries learn about such problems if nobody poses them.*
For those who are interested in well-known problems in China.
Thank [user:Elegia,2020-04-23] and [user:djq_cpp,2020-04-23] for developing this technique. Thank [user:tEMMIE.w.,2020-04-23] for reviewing this article.
####[Chain Reaction](http://uoj.ac/problem/50) in UOJ Round 3 By [user:vfleaking,2020-04-23]
**Statement**
You are given a set $A$, you need to compute $g_{i} = \frac{1}{2} \sum_{j,k}{i-1 \choose j}{i-1-j \choose k} g_jg_k$ where $i-1-j-k \in A$.
**Solution**
Let the EGF of $g$ be $x(t)$ and EGF of $A$ be $a(t)$. Thus $x'(t)=\frac{1}{2} a(t) x^2(t)+1$. We can solve this equation by D&C and FFT in $O(n\log^2 n)$. But there is a <s>slower</s> solution in $O(n\log n)$.
For a polynomial equation $f(x(t))=0$, we can use the Newton's method to solve it. If we find ...
####[Pearl](https://loj.ac/problem/3120) in CTSC 2019 By
[user:laofudasuan,2020-04-23]
15.
Self-deception: maybe why you're still grey after practicing every day I generally don't like to give much advice on "how to practice", but recently I have been thinking a lot about this and I realized that there is something that I believe affects a lot of people (though it is admittedly hard to tell) that barely gets talked about: self-deception.
Self-deception is a devious thing. It can be very hard to detect, yet can be fatal to improvement.
This blog is mainly directed to greys, greens and cyans that can't get out of these categories. Most examples are given with that in mind. That being said, I believe others have something to think about as well.
This is my first blog on such "psychological issues" and I don't know if I'll ever make another one. It's certainly a difficult topic to write about because for most of the blog, the message is "your practice is not as good as you think it is" or even "you aren't as good as you think you are" which can of course be a hard thing to hear. Thus, I have to somehow be very gentle while getting the poin...
Let me tell you something about my practice history. Somewhere in late 2019 and
early 2020 I
16.
IOI vs CF performance: 2024 Edition <blockquote>
CF ratings are unrelated to your IOI results. CF contests differ significantly from IOI contests.
</blockquote>
❌ **Wrong!**
A higher CF rating, with a gap of at least 100, correlates with an **87%** chance of achieving a better placement at IOI. In fact, the relationship between IOI placement and CF rating is strongly connected. The [Pierson Correlation Coefficient](https://en.wikipedia.org/wiki/Pearson_correlation_coefficient) for these two factors is -0.83.
<center>
<be>
<a href="https://algoritmiacademy.com/wp-content/uploads/2024/10/output_at_ioi.png">
<img width="80%" src="https://algoritmiacademy.com/wp-content/uploads/2024/10/output_at_ioi.png">
</a>
<br>
<i>Correlation between CF rating and IOI placement</i>
</center>
❗ What is that outlier participant on the top-right? He is Jiyu Shen ([user:PubabaOnO,2024-10-02]), with CF rating of 3000+, but it seems that he was unable to attend the contest 💔
Here are the statistics...
updated prediction. Check out the similar blog for IOI 2019
[here](https://codeforces.me/blog/entry, Check out the similar blog for IOI 2019
[here](https://codeforces.me/blog/entry/68981).
17.
Codeforces Round #556 Hi Codeforces!
I'm so happy to invite you to [contest:1149] and [contest:1150]! The rounds will be held on [contest_time:1149]. The round will be rated for both divisions. (At least that's what I've been told!)
The problems were written and prepared by me.
Thanks to [user:300iq,2019-04-27] for the round coordination, and to [user:Radewoosh,2019-04-27] for his invaluable help with choosing the problemset and testing the problems!
Also, I want to give a shout-out to [user:MikeMirzayanov,2019-04-27] for his amazing Codeforces and Polygon platforms!
_My browser's tab bar, right now._
You'll work on **5** problems, and you will have **2** hours to solve them. The scoring distribution will be revealed closer to the round.
~~~~~
def get_end_remark():
return random.choice([
"Wish everyone high ratings!",
"Good luck!",
"Have fun!",
"Please, read all the problems!"])
~~~...
I've been told!) The problems were written and prepared by me. Thanks to
[user:300iq,2019-04-27, 1. [user:Um_nik,2019-04-29] 2. [user:Vn_nV,2019-04-29] 3. [user:maroonrk,2019
-04-29] 4, 1. [user:jiangly,2019-04-29] 2. [user:Simplicity,2019-04-29] 3.
[user:Netherdrake,2019-04-29] 4, Also, thanks to [user:_kun_,2019-04-29], [user:V--gLaSsH0ldEr593--V,2019-04-29]
and, The problems were written and prepared by me. Thanks to [user:300iq,2019-04-27]
for the round, ](https://codeforces.me/contest/1150/problem/A) | 1:57 | [user:Ahmad,2019
-04-29] | | | | [Tiling
18.
Good Bye 2018 The end of the December is fast approaching and it is time for the <strike>best</strike> last contest of the year! The Good Bye 2018 round will take place on [Sunday, December 30, 2018 at 14:35 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=30&month=12&year=2018&hour=17&min=35&sec=0&p1=166).
As the people who already engaged in [discussions about the ultimate problem](https://codeforces.me/blog/entry/64025) suspect, I am the problem writer. As such, I'd like to thank to:
- [user:arsijo,2018-12-26] and [user:KAN,2018-12-26] for the round coordination and one of the problems,
- [user:AlexFetisov,2018-12-26], [user:cyand1317,2018-12-26], [user:Errichto,2018-12-26], [user:Jeel_Vaishnav,2018-12-26], [user:lewin,2018-12-26], [user:misof,2018-12-26], [user:winger,2018-12-26] for testing and invaluable suggestions,
- [user:MikeMirzayanov,2018-12-26] and everyone involved in building and running Codeforces and Polygon platform.
The round will last for 2:30 hours and...
UPD: The top 3 participants eligible for ICPC 2019/20 season [can win a great
prize](https
Анонс Good Bye 2018
19.
New contest format?! Stream feat. tourist, Um_nik Hey all!
We've created a new 1v1 programming contest format: **Lockout**. Like in most contests, each round has a set of problems and contestants work to solve them as quickly as they can. In Lockout, however, contestants compete head-to-head and only the first contestant to solve each problem gets the points. Contestants can work on problems in any order, so speed and strategy are crucial to avoid getting sniped! The head-to-head action also makes the contest much more exciting for viewers.
We ran the first edition of Lockout at TCO Finals last month as a double-elimination bracket [tournament](https://challonge.com/lockout0). All of the finalists who were available competed (and even some of the problem writers) and we got to see a lot of exciting back-and-forth matches! As you can see though, there's still one set left to play. So we'll be streaming **Grand Finals of Lockout 0 featuring [user:tourist,2019-12-28] vs. [user:Um_nik,2019-12-28]** at [9:30 AM PST](https://www.timea...
featuring [user:tourist,2019-12-28] vs. [user:Um_nik,2019-12-28]** at [9:30 AM
PST](https
20.
Codeforces Global Round 4 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Hi!
On [contest_time:1178] we will host [contest:1178].
It is the fourth round of a new series of [Codeforces Global Rounds](https://codeforces.me/blog/entry/65002) supported by XTX Markets. The rounds are open for everybody, the rating will be updated for everybody.
You will be given 8 problems and 150 minutes to solve them. The scoring distribution will be **500-750-1250-1750-2000-(1500+1500)+3250+4000**.
The prizes for this round:
- 30 best participants get a t-shirt.
- 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.
The prizes for the 6-round series in 2019:
- In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT).
- The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
...
серии из 6 раундов в 2019 году: - За каждый раунд лучшим 100 участникам
начисляются баллы согласно, - [user:arsijo,2019-07-16] for his help in the round's coordination, -
[user:300iq,2019-07-18, - [user:arsijo,2019-07-16] за координирование раунда, - [user:300iq,2019
-07-18], [user:Aleks5d, 1. [user:ainta,2019-07-20] 2. [user:Radewoosh,2019-07-20] 3. [user:tzuyu_chou,
2019-07-20] 4, The prizes for the 6-round series in 2019:, Призы в серии из 6 раундов в 2019 году:
21.
[Tutorial] Collection of little techniques #### Introduction
There are a number of "small" algorithms and facts that come up again and again in problems. I feel like there I have had to explain them many times, partly because there are no blogs about them. On the other hand, writing a blog about them is also weird because there is not that much to be said. To settle these things "once and for all", I decided to write my own list about about common "small tricks" that don't really warrant a full tutorial because they can be adequately explained in a paragraph or two and there often isn't really anything to add except for padding.
This blog is partly inspired by [user:adamant,2022-03-15]'s [blog](48417) from a few years ago. At first, I wanted to mimic adamant's blog structure exactly, but I found myself wanting to write longer paragraphs and using just bolded sentences as section headers got messy. Still, each section is short enough that it would not make much sense to write separate blogs about each of these things.
A...
Riga/Singapore 2019, 300iq contest. I don't know if you can submit it anywhere., This problem is from ICPC Manila 2019 and also, This problem is from Algorithmic Engagements. I know this problem from ["best
problem in2019
22.
Codeforces Global Rounds Hello!
It is always satisfying and important for me when former contest participants offer their help to the community and support the development of programming competitions. And now I am in a hurry to share the news that thanks to the support of <a href="https://www.xtxmarkets.com/">XTX Markets</a> and the personal participation of Yuri Bedny and Alexander Gerko, we are launching a new line of Codeforces Global Rounds. Hooray!
<img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Like many of you, I had never heard of <a href="https://www.xtxmarkets.com/">XTX Markets</a> before but it is one of the largest quantitative-driven electronic liquidity providers in the world. I understand little about the financial sector, but with their 34,148 cores and 42 petabytes of usable storage in their research cluster, XTX’s rapid growth and strong market share globally speak for themselves.
So, in 2019, w...
личному участию Юрия Бедного и Александра Герко в 2019-м году мы запускаем
новую линейку раундов, участию Юрия Бедного и Александра Герко в 2019-м году мы запускаем новую
линейку раундов Codeforces Global, So, in 2019, with the support of XTX Markets, 6 rounds of the new Codeforces
Global Rounds will be, Итак, в 2019-м году при поддержке XTX Markets будет проведено 6 раундов новой
линейки Codeforces, — [user:MikeMirzayanov,2019-02-04]
23.
Codeforces Round #600 (Div. 2) Hello, Codeforces!
I'm glad to invite you to [contest:1253], which will be held on [contest_time:1253]. It will be **rated for all participants with rating below 2100**. You will be given **six problems** and **two hours** to solve them. As usual, the score distribution will be announced shortly before the round.
The problems were invented and prepared by me. Huge thanks to:
- [user:faremy,2019-11-14] for taking time to solve and give me precious feedback on most of the problems I have considered putting into my round throughout its whole creation (more than 6 months!)
- [user:300iq,2019-11-14] for coordinating the round and giving helpful advices
- [user:MikeMirzayanov,2019-11-14] for great systems Polygon and Codeforces
- [user:dorijanlendvaj,2019-11-14], [user:McDic,2019-11-14], [user:nvmdava,2019-11-14], [user:_Kuroni_,2019-11-14], [user:fedoseev.timofey,2019-11-14], [user:Nebuchadnezzar,2019-11-14], [user:opukittpceno_hhr,2019-11-14], [user:aneesh2312,2019-11-14]...
- A. [user:teapotd,2019-11-16] (2 minutes) - B. [user:nitrousoxide,2019-11-16]
(7 minutes) - C, - [user:300iq,2019-11-14] for coordinating the round and giving helpful advices, - [user:MikeMirzayanov,2019-11-14] for great systems Polygon and Codeforces, - [user:dorijanlendvaj,2019-11-14], [user:McDic,2019-11-14], [user:nvmdava,2019
-11-14], [user, - [user:faremy,2019-11-14] for taking time to solve and give me precious
feedback on most of the, 1. [user:Um_nik,2019-11-16] (solved all problems in 38 minutes!) 2.
[user:dreamoon_love_AA,2019-11, 1. [user:whyzker,2019-11-16] 2. [user:root_power_6,2019-11-16] 3. [user:SeranOZ,
2019-11-16] 4
24.
Codeforces Round #572 Привет, Codeforces!
Мы рады пригласить вас на [Codeforces Round #572](https://codeforces.me/contests/1188,1189), который состоится в [пятницу, 5 июля в 18:05](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20190705T1805&p1=166&ah=2). Раунд будет рейтинговым для обоих дивизионов (так как [user:MikeMirzayanov,2019-06-29] спасибо в этот раз мы сказали).
Раунд готовили мы, [user:antontrygubO_o,2019-06-29] и [user:kefaa2,2019-06-29]. Это наш первый контест, и, надеемся, не последний!
Спасибо [user:arsijo,2019-06-29] за отличное координирование раунда, [user:gepardo,2019-06-29], [user:GandalfTheGrey,2019-06-29], [user:progmatic2,2019-06-29], [user:zoomswk,2019-06-29], [user:ecnerwala,2019-06-29], [user:AllCatsAreBeautiful,2019-06-29], [user:DmitryGrigorev,2019-06-29], [user:Markellonchik,2019-06-29], [user:dasfex,2019-06-29], [user:Taran_1407,2019-07-01], [user:slicedclementines,2019-07-01], [user:DenisPushkin,2019-06-30], [user:austrian_artist,2019-07-01], [user:mmel...
[user:MikeMirzayanov,2019-06-29] спасибо в этот раз мы сказали)., thanked [user:MikeMirzayanov,2019-06-29])., **1.** [user:Um_nik,2019-07-05], **1.** [user:esbee,2019-07-05], **2.** [user:handsomeIvan,2019-07-05], **3.** [user:Radewoosh,2019-07-05], **3.** [user:philologist,2019-07-05], **4.** [user:Marcin_smu,2019-07-05], **4.** [user:teamskiy,2019-07-05], **5.** [user:Endagorion,2019-07-05], **5.** [user:NeoGul,2019-07-05], A lot of thanks to [user:arsijo,2019-06-29] for the excellent coordination of
the round, Round was prepared by us, [user:antontrygubO_o,2019-06-29] and
[user:kefaa2,2019-06-29]. This is, Раунд готовили мы, [user:antontrygubO_o,2019-06-29] и [user:kefaa2,2019-06-29].
Это наш первый, Спасибо [user:arsijo,2019-06-29] за отличное координирование раунда,
[user:gepardo,2019-06-29
25.
Codeforces: Итоги 2018 Привет, Codeforces!
На календаре уже февраль 2019-го, а это значит, что с отчётом за 2018-й год я припоздал. Приболел, разъезды — и вот результат. Лучше поздно, чем никогда! Давайте вспоминать прошлый год.
В 2018-м году к коллективу координаторов присоединились [user:_kun_,2019-02-05], [user:300iq,2019-02-05] и [user:arsijo,2019-02-05]. Работу координаторов возглавляет (и является координатором координаторов) [user:KAN,2019-02-05]. Я очень надеюсь, что более размеренный график подготовки раундов большим коллективом координаторов даст лучше вникать задачи. Основные нововведения в платформе реализованы мной и разработчиками [user:kuviman,2019-02-05], [user:fcspartakm,2019-02-05], [user:MaximShipko,2019-02-05]. Большую работу по организации мероприятий и рассылке призов оказала [user:gKseni,2019-02-05].
Отдельное спасибо авторам задач и тестерам. Именно ваш контент заряжает сообщество жизнью и объединяет всех нас. Спасибо вам за задачи!
А теперь подведём итоги 2018-го го...
will try to please you in 2019!, порадовать вас и в 2019-м году!, February 2019 is already on the calendar, which means that I was late with the
report for 2018, I hope that in 2019 we will continue to work together with old partners and
find new friends. Have, In 2018, [user:_kun_,2019-02-05], [user:300iq,2019-02-05] and [user:arsijo,2019
-02-05] joined the, В 2018-м году к коллективу координаторов присоединились [user:_kun_,2019
-02-05], [user:300iq,2019, На календаре уже февраль 2019-го, а это значит, что с отчётом за 2018-й год я
припоздал. Приболел, Я надеюсь, что в 2019-м году мы продолжим совместную работу со старыми
партнёрами и наёдем новых, — [user:MikeMirzayanov,2019-02-05]
26.
On problemsetting 2 [Previous part](https://codeforces.me/blog/entry/70178)
Hi there again! Previous part with opinions of some amazing problemsetters turned out to be interesting for you, so I decided to gather some more opinions :D. I really hope that this post will help someone in their problemsetting future!
#### When and how did you start problemsetting?
[user:300iq,2020-01-11]: April, 2017
[user:maroonrk,2020-01-11]: In 2015 Summer, I hold the first contest with friends at high school club. It was a local Japanese contest.
[user:Radewoosh,2020-01-11]: In high school, so probably for 5 years. I was creating problems for other people from my school as my teacher told me that it's a completely different point of view.
[user:voidmax,2020-01-11]: It was 3 years ago. I was on plane and I didn't have a clue what to do in my free time. Then I realized that I can try myself in problemsetting. Later I created first and one of my favorite problem ([problem:963B]). I was full of inspiration a...
#### What are your favorite problems of 2019?, Поиск идеи (ROI 2019, LOL.)
27.
Codeforces Round #547 (Div. 3) Привет, Codeforces!
Я рад пригласить вас на [contest:1141], который начнётся во [contest_time:1141]. К официальному участию приглашаются все, чей текущий рейтинг строго меньше 1600. Все остальные — могут принять участие вне конкурса.
Так получилось, что расписание этого месяца не пестрит раундами (координаторы, мы надеемся на вас!), и поэтому я решил частично исправить ситуацию. Все задачи этого раунда придуманы и подготовлены мной в последний день сборов [Hello Muscat Programming Bootcamp 2019](/blog/entry/63298) и в перелетах из Маската в Санкт-Петербург. Я даже специально засёк время на подготовку: к текущему моменту (задачи готовы к тестированию) я потратил около 6 часов на их подготовку, включая придумывание некоторых из задач. Мне очень нравится работать над задачами, это что-то на стыке творчества и программирования. Очень надеюсь, что вам понравится результат моей работы.
<center>
<br/>
<img src="/predownloaded/76/ea/76eaf024dd0f6321a74e266ed77baad33aac32c0.png...
Bootcamp 2019](/blog/entry/63298) и в перелетах из Маската в Санкт-Петербург.
Я даже специально засёк, I only plan to give the round to testing. Many thanks to the testers
[user:ivan100sic,2019-03-18, of [Hello Muscat Programming Bootcamp 2019] (/blog/entry/63298) and on flights
from Muscat to St, только планирую отдать раунд в тестирование. Спасибо тестерам [user:ivan100sic,
2019-03-18, Good luck on the round
— [user:MikeMirzayanov,2019-03-17], Удачи на раунде,
— [user:MikeMirzayanov,2019-03-17]
28.
Happy 2019 Year! <img style="float:right; margin: 0 1em 1em 1em;" src="https://cdn.shortpixel.ai/client/q_lossless,ret_img/https://programmingforsuccess.in/wp-content/uploads/2017/09/2019-happy.jpg">
Congratulations to all the new 2019 year! At this very moment you can make an important wish. Done? I wish it to be fulfilled!
I wish you to become better in the new year, to think better and to meet less often with bugs and mistakes. Let all your solutions be fast, effective and correct!
Later, I will compile statistics for 2018 and publish in the form of an annual report
Now I'd like to remind you most voted posts of 2018. Here is the list of the top 15:
* <a href="/blog/entry/62865">Codeforces: Problem Difficulties</a> by me, +3158
* <a href="/blog/entry/63375">Codeforces: Our Steps After DDOS Attack</a> me, +2995
* <a href="/blog/entry/56954">Hello 2018</a> by [user:tourist,2018-12-31], +2848
* <a href="/blog/entry/59228">Codeforces: Updates in rating and rounds</a> by me, +1973
* <a...
Happy 2019 Year!, ,ret_img/https://programmingforsuccess.in/wp-content/uploads/2017/09/2019
-happy.jpg, Congratulations to all the new 2019 year! At this very moment you can make an
important wish. Done
29.
Codeforces Round #732 Hello, Codeforces!
I'm glad to invite you to [contest:1545] and [contest:1546], which will be held on [contest_time:1545]. **Note the unusual start time of the round.**
The round will be rated for both divisions. Each division will have **6 problems** and **2.5 hours** to solve them. There may or may not be an interactive problem, so I suggest you should read the [guide for interactive problems](https://codeforces.me/blog/entry/45307).
All problems were written and prepared by [user:CoupDeGrace,2021-07-02], [user:kuangbin,2021-07-02], [user:mejiamejia,2021-07-02], [user:Heltion,2021-07-02], [user:Melacau,2021-07-02], [user:Nanako,2021-07-02], [user:GOATWU,2021-07-02], [user:Cirno_9baka,2021-07-02], [user:Suiseiseki,2021-07-02], [user:ODT,2021-07-02], [user:box,2021-07-03], [user:Ynoi,2021-07-02], [user:syh0313,2021-07-02], [user:wh0816,2021-07-02] and me.
And thanks to [user:QAQAutoMaton,2021-07-02], [user:gamegame,2021-07-02], [user:starusc,2021-07-02], [user:interesting...
round coordination and help with preparation and [user:MikeMirzayanov,2019
-05-10] for great systems
30.
My winning theory in IOI 2018 & 2019 — Why I won 2 golds in IOI Dear Codeforces community.<br />
According to [IOI 2019 Results](http://stats.ioinformatics.org/results/2019), I got the 25th place and got successful gold medals twice in a row.<br />
Although it was pretty close to the gold-medal border (only 6.14pts / 600 difference) and it was lower performance than IOI 2018, which I participated when I was orange in Codeforces, I had many chances to get more points in this IOI, even for top 10. Since there are not so many people who have got two gold medals in IOI (and there were many requests like "I want [user:E869120,2019-08-14] to talk about how to get gold in IOI" like [this comment](https://codeforces.me/blog/entry/66909?#comment-510127) and [this comment](https://codeforces.me/blog/entry/66909?#comment-513129)). I want to write something about IOI, which may be useful for people who will participate in IOI next year and also some years later.<br />
<br />
<br />
### A. First of all
At...
My winning theory in IOI 2018 & 2019 — Why I won 2 golds in IOI, ### E. Results of strategy In IOI 2019, I finally got the gold medal. But there
is an interesting, ### F. How I succeeded to gain concentration and mental toughness In IOI 2019,
I got gold because, > IOI 2019 100 40 50 53 66, > IOI 2019 100 40 72 71 100, Dear Codeforces community.
According to [IOI 2019 Results](http://stats.ioinformatics.org, ](https://oj.uz/problem/view/IOI15_boxes), [IOI 2019
Shoes](https://ioi2019.az/source/Tasks/Day1
31.
ICPC Finals 2019 <img src="/predownloaded/02/25/02253adce36abb83bcaedca3cd1498b9d459d90d.png" style="margin: 0 0 0 1em; float: right;">
ICPC World Finals 2019 will begin on <a href="https://www.timeanddate.com/worldclock/fixedtime.html?msg=ICPC+World+Finals+2019&iso=20190404T12&p1=320&ah=5">April 4, 2019 at 11:00 (UTC)</a>.
This event is the main event of the year in the world of sports programming!
In the past 20 years alone, ICPC participation has increased by more than 2000%. The contest evolved into its present form as a multi-tier competition in 1977, with the first finals held in conjunction with the ACM Computer Science Conference. Last year, ICPC Regional
participation included 52,709 of the finest students and faculty in computing disciplines from 3,233 universities in 110 countries.
We remind you that in the current world champion is the team of Moscow State University.
Codeforces wishes the teams to show a vivid and interesting contest. We wish to find beautiful solutions, write ...
ICPC Finals 2019, ICPC Финал 2019, ICPC World Finals 2019 English Broadcast:
, Legends Live Stream ([user:Endagorion,2019-04-04] + [user:Petr, 4-го апреля 2019 г. в , ICPC World Finals 2019 will begin on
32.
Праздник к нам приходит! Подарки 2019! <img src="https://codeforces.me/predownloaded/21/66/2166e92dd3e8a1a3a9d6f5816deb3a306e1307d6.png" style="float:right; width:400px; margin: 0 1em 1em 1em;"/>
У вас же уже новогоднее настроение?
А у нас традиционные подарки!
#### <img src="https://assets.codeforces.com/images/wand.png"/> Смена хэндла
В Новый год мечты сбываются: вы можете сменить хэндл до 10-го января!
Открыта традиционная новогодняя акция. Спешите! Только до 10-го января вы можете изменить свой хэндл абсолютно безвозмездно, то есть даром! Сменить
хэндл можно лишь <b><i>единожды</i></b>. Обратите внимание, что откатить изменения или изменить хэндл еще раз вы сможете
только через год. Будьте внимательны и осторожны со своими желаниями! :)
Хэндл можно сменить либо на совсем новый (ранее никем никогда не используемый), либо на тот, который у вас был когда-то ранее. Кстати, ссылки
на ваш профиль с прошлым хэндлом работать не перестанут — будет автоматический редирект со старого хэндла на новый.
У ...
Праздник к нам приходит! Подарки 2019!
33.
Codeforces Round #530 Всем привет!
Сейчас проходит зимняя смена ЛКШ (Летней Компьютерной Школы), и мы в составе параллели А+ с ее преподавателями подготовили полноценный Codeforces Round.
Раунд состоится в [contest_time:1098] и продлится 2.5 часа. В каждом дивизионе будет предложено по 6 задач.
Задачи раунда были придуманы и подготовлены [user:300iq,2019-01-04], [user:scanhex,2019-01-04], [user:cookiedoth,2019-01-04], [user:allrats,2019-01-04], [user:osaaateiasavtnl.,2019-01-04], [user:Qlukva,2019-01-04], [user:Forestryks,2019-01-04], [user:Dimon,2019-01-04], [user:LordVoldebug,2019-01-04], [user:romanovsavelij,2019-01-04], [user:golub,2019-01-04], [user:ismagilov.code,2019-01-04],[user:alexey_kuldoshin,2019-01-04], [user:LadyPython,2019-01-05], [user:UnstoppableSolveMachine,2019-01-05] под руководством преподавателей [user:izban,2019-01-04], [user:VArtem,2019-01-04], [user:_meshanya_,2019-01-04], [user:pashka,2019-01-04].
Также спасибо за тестирование раунда [user:isaf27,2019-01-04], [user:isaf...
были придуманы и подготовлены [user:300iq,2019-01-04], [user:scanhex,2019
-01-04], [user:cookiedoth, **UPD**: так как регистрация открывается раньше пересчета рейтинга Hello 2019,
в случае изменения, . The tasks of the round were invented and prepared by [user:300iq,2019-01-04],
[user:scanhex, Also thanks for testing [user:isaf27,2019-01-04], [user:isaf27_loves_me,2019
-01-04, And, of course, thanks to [user:MikeMirzayanov,2019-01-04] for great systems
Codeforces and Polygon., The tasks of the round were invented and prepared by [user:300iq,2019-01-04],
[user:scanhex,2019, Задачи раунда были придуманы и подготовлены [user:300iq,2019-01-04],
[user:scanhex,2019-01-04, И, конечно же, спасибо [user:MikeMirzayanov,2019-01-04] за великолепные системы
Codeforces и, Также спасибо за тестирование раунда [user:isaf27,2019-01-04],
[user:isaf27_loves_me,2019-01-04
34.
Codeforces Round #789 Hello, Codeforces! ฅ(*`ω´*)ฅ
We are glad to invite you to take part in [contest:1677] and [contest:1678], which will be held on [contest_time:1677].
The round will be **rated** for all participants from both divisions. Participants in each division will be offered **6** problems and **2** hours to solve them. Both divisions will share 4 problems.
The problems were written and prepared by [user:funer,2022-05-05], [user:dark_light,2022-05-05], [user:FreshP_0325,2022-05-05], [user:Frank_DD,2022-05-05], [user:qsmcgogo,2022-05-05], [user:winterzz1,2022-05-05], [user:Heltion,2022-05-05], [user:TomiokapEace,2022-05-05] and me.
Thank to:
- [user:74TrAkToR,2022-05-05] for excellent coordination of this round! And translating the statements to Russian.
- [user:KAN,2022-05-08] for helping us to review and fix some statements.
- [user:TomiokapEace,2022-05-05] for helping us to translate **all** the statements and tutorials to English.
- [user:Heltion,2022-05-05] for giving...
- [user:MikeMirzayanov,2019-05-16] and his Codeforces team for amazing systems
Codeforces and
35.
[Tutorial] Пересечение матроидов простыми словами **[This article is also available in [English](https://codeforces.me/blog/entry/69287?locale=en)]**
Привет, CodeForces.
Я думаю, что матроиды — это прекрасные и очень мощные структуры, однако, не настолько хорошо известные в спортивном программировании.
Я познакомился с матроидами на Зимних Петрозаводских Сборах 2019. Там была задача, которая очевидно не решалась обычными способами, известными мне тогда. Разбор этой задачи состоял буквально из трех слов “just matroid intersection”. Тогда мне потребовалось больше двух дней дорешивания чтоб найти всю необходимую информацию и детали и написать решение, которое получает Accepted. И намного больше времени мне потребовалось чтобы понять почему это действительно работает и как именно это работает. (Я до сих пор сомневаюсь в некоторых деталях.)
Конечно, совершенно не трудно нагуглить все необходимые определения и статьи, связанные с этой темой, но мне кажется, что все они больше сконцентрированы на математической теории, с...
I’ve discovered matroids at 2019 Petrozavodsk Winter Training Camp. There was a
problem that, Я познакомился с матроидами на Зимних Петрозаводских Сборах 2019. Там была
задача, которая очевидно
36.
Dasha Code Championship Finals and Mirror Round 588 Announcement Hello everybody! A new round is upcoming and I'm honored to be its author. The round will first appear as the onsite for Dasha.AI Code Championship and later we will hold a rated mirror. Everybody is welcomed to participate in Codeforces and I wish good luck for people in Saint Petersburg and Novosibirsk.
Using the opportunity, I want to thank:
- [user:mnbvmar,2019-01-02] for helping in the preparation of a great part of everything. Really, without you, I wouldn't do it.
- [user:300iq,2019-01-02] for coordination and help with preparation.
- As always, [user:MikeMirzayanov,2019-01-02] for taking care of international competitive programming and making such great platforms as Codeforces and Polygon.
- [user:KAN,2019-09-24], [user:zscoder,2019-09-24], [user:Lewin,2019-09-24], [user:JeffreyHo,2019-09-24], [user:Darkstalker,2019-09-24], [user:Darko,2019-09-24] and [user:Gtaumaturgo,2019-09-24] for testing the problems and great advice.
- [Dasha.Ai](https://dasha.ai/en/) for an or...
Novosibirsk. Using the opportunity, I want to thank: - [user:mnbvmar,2019
-01-02] for helping in the, - [user:mnbvmar,2019-01-02] for helping in the preparation of a great part of
everything. Really, 1. [user:Timonnable,2019-09-24] 2. [user:Pechalka,2019-09-24] 3. [user:Maho,2019
-09-24], 1. [user:Um_nik,2019-09-24] 2. [user:yosupo,2019-09-24] 3.
[user:ksun48,2019-09-24], 1. [user:aid,2019-09-24] 2. [user:V--gLaSsH0ldEr593--V,2019-09-24] 3.
[user:cookiedoth,2019-09-24], 1. [user:lqs2o15,2019-09-24] 2. [user:rainboy,2019-09-24] 3. [user:TomiokaGiyuu,
2019-09-24]
37.
Codeforces Round #599 Hi guys!
Glad to invite you to <a href="/contests/1242">Codeforces Round #599</a> to be held this [contest_time:1242]!
My name is Evgeny Vihrov, this is already my 6th Codeforces contest as an author. To introduce myself, I have participated twice in the ACM ICPC Finals (2012, 2014) and currently I am co-coaching teams for the ICPC at the University of Latvia. This is my first solo round, and it took 3.5 years to make! (the last one was #347 with [user:Alex_2oo8,2019-11-04]).
In this contest you will have to help Ujan deal with his renovation issues. Hopefully, everyone will find a problem matching their taste!
Huge thanks to [user:arsijo,2019-11-04] for coordinating the preparation of the contest and for the patience with the frequent delays. :) Thanks to [user:Xellos,2019-11-04], [user:Origenes,2019-11-04], [user:KAN,2019-11-04] and [user:opukittpceno_hhr,2019-11-06] for generously testing the round. And as always, thanks to [user:MikeMirzayanov,2019-11-04] for the <s>pan...
problem matching their taste! Huge thanks to [user:arsijo,2019-11-04] for
coordinating the, сможет найти задачу по своему вкусу! Огромное спасибо [user:arsijo,2019-11-04]
за координацию, **UPD1:** [user:McDic,2019-11-05] is joining as a coauthor of the contest
(reasons to be revealed, **UPD1:** [user:McDic,2019-11-05] присоединяется как соавтор раунда (причины
будут прояснены позже)!, **UPD5:** The reason behind [user:McDic,2019-11-06] entering as a coauthor is
that one problem was, **UPD5:** Причина тому, что [user:McDic,2019-11-06] присоединился как соавтор,
в том, одна задача, 1. [user:Benq,2019-11-06] 2. [user:wxhtxdy,2019-11-06] 3. [user:ecnerwala,2019
-11-06] 4, 1. [user:hakobdilif,2019-11-06] 2. [user:is1813r,2019-11-06] 3. [user:Fype,2019
-11-06] 4, Huge thanks to [user:arsijo,2019-11-04] for coordinating the preparation of the
contest and for the, Огромное спасибо [user:arsijo,2019-11-04] за координацию раунда и терпение во
время многочисленных
38.
Codeforces Round #569 Привет, Codeforces!
Я рад пригласить всех на [contest:1179] и [contest:1180], которые состоится завтра, [в пятницу, 21 июня 2019 г. в 19:35](https://www.timeanddate.com/worldclock/fixedtime.html?day=21&month=6&year=2019&hour=19&min=35&sec=0&p1=166). Раунд будет рейтинговым для обоих дивизионов.
Это второй контест от нашего проекта "Обсуждаем задачи". Если у вас есть интересные задачи, то, пожалуйста, присылайте их нам, и, если они окажутся хорошими, вскоре мы дадим их на аналогичный раунд. Вот ссылка на [программный пост](https://codeforces.me/blog/entry/65110).
Свои задачи на раунд предложили Иван [user:ScreaMood,2019-06-20] Фёдоров, Кирилл [user:Choopa_choops,2019-06-20] Бессонов, Мухаммаджон [user:Mr.Hakimov,2019-06-20] Хакимов, Федор [user:osaaateiasavtnl.,2019-06-20] Ушаков, Фёдор [user:Kuyan,2019-06-20] Куянов и я, Дмитрий [user:DmitryGrigorev,2019-06-20] Григорьев.
Раунд готовили мы, Дмитрий [user:DmitryGrigorev,2019-06-20] Григорьев, Фёдор [user:osaaateiasavtnl.,20...
завтра, [в пятницу, 21 июня 2019 г. в
19:35](https://www.timeanddate.com/worldclock/fixedtime.html, июня 2019 г. в
19:35](https://www.timeanddate.com/worldclock/fixedtime.html?day=21&month=6&year=
2019, 1. [user:PSMaoTheKingOfAzerbaijan,2019-06-22], 1. [user:Radewoosh,2019-06-22], 2. [user:ACRush,2019-06-22], 2. [user:atacan,2019-06-22], 3. [user:Shayan.Kashefi_A,2019-06-22], 3. [user:ecnerwala,2019-06-22], 4. [user:LiPro,2019-06-22], 4. [user:mango_lassi,2019-06-22], 5. [user:BrutBurger,2019-06-22], 5. [user:neal,2019-06-22], Problems for the round have been proposed by Ivan [user:ScreaMood,2019-06-20]
Fedorov, Kyrill, The round have been prepared by us, Dmitry [user:DmitryGrigorev,2019-06-20]
Grigoryev, Fedor, We'd like to give thanks to Ildar [user:300iq,2019-03-09] Gainullin for
excellent coordination of, ], which will be held [on Friday, June 21, 2019, at
19:35](https://www.timeanddate.com/worldclock, Раунд готовили мы, Дмитрий [user:DmitryGrigorev,2019-06-20] Григорьев, Фёдор
[user:osaaateiasavtnl, Свои задачи на раунд предложили Иван [user:ScreaMood,2019-06-20] Фёдоров, Кирилл, Спасибо Ильдару [user:300iq,2019-03-09] Гайнуллину за отличное координирование
раунда, Sooke
39.
Manthan — Codefest'19 Hello Codeforces!
I would like to invite you to [Manthan, Codefest'19](https://codeforces.me/contests/1208), which will take place on [Sunday, August 25, 2019 at 8:05 PM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Manthan%2C+Codefest%2719&iso=20190825T1435&ah=2). This is a **combined Div. 1 + Div. 2** round and is **rated** for participants from both divisions.
The Department of Computer Science and Engineering, IIT (BHU) is conducting Codefest from 23rd August — 25th August. Manthan, the algorithmic programming contest under the banner of [Codefest](https://codefest.tech/), is being held as a special Codeforces round. The round follows regular Codeforces rules.
All problems in this round were created and prepared by [user:drastogi21,2019-08-23], [user:_shanky,2019-08-23], [user:enigma27,2019-08-23], [user:navpun31,2019-08-23], [user:KAN,2019-08-23] and me ([user:hitman623,201...
**1.** [user:tourist,2019-08-25], **2.** [user:Um_nik,2019-08-25], **3.** [user:wxhtxdy,2019-08-25], **A.** [user:IgorI,2019-08-28], **B.** [user:Geothermal,2019-08-25], **C.** [user:icecuber,2019-08-25], **D.** [user:ILoLy,2019-08-25], **E.** [user:nocriz,2019-08-25], **F.** [user:GoGooLi,2019-08-25], **G.** [user:wxhtxdy,2019-08-25], **H.** [user:tourist,2019-08-28], **UPD:** We decided to give the 8th T-shirt to [user:IgorI,2019-08-28] for
problem A. Congrats!, ,2019-08-23], [user:enigma27,2019-08-23], [user:navpun31,2019-08-23], [user:KAN,
2019-08-23] and me, /contests/1208), which will take place on [Sunday, August 25, 2019 at 8:05 PM
IST](https, A lot of thanks to [user:KAN,2019-08-23], [user:300iq,2019-08-23],
[user:V--gLaSsH0ldEr593--V,2019
40.
CEOI 2019 Mirror [The 26th Central European Olympiad in Informatics](https://ceoi.sk/) will take place in Bratislava, Slovakia, during **July 23rd-29th 2019**. The most gifted high school students from 13 countries will have the opportunity to prove their knowledge and skills in informatics.
Codeforces will organise the online mirror for this year's competition. The online mirrors will take place after the finish of each of the 2 competition days, having the same scoring format.
The online mirror schedules are the following:
- [contest_time:1192]
- [contest_time:1193]
**Contest format**
- The contest will be unrated for all users.
- You will have to solve 3 tasks in 5 hours.
- There will be full feedback throughout the entire contest.
- The scoreboard will be hidden until the end of the contest.
- The tasks will have partial scoring. The maximum score for each problem will be 100 points.
- Among multiple submissions only the one that achieves the maximum score is counted towards t...
CEOI 2019 Mirror, [user:arsijo,2019-07-27]. Many thanks!, , Slovakia, during **July 23rd-29th 2019**. The most gifted high school
students from 13 countries, 1. [user:mnbvmar,2019-07-28] 300 1. [user:Benq,2019-07-28] 300 3.
[user:gamegame,2019-07-28] 281, 1. [user:zx2003,2019-07-28] 230 1. [user:saba2000,2019-07-28] 230 2. [user:TLE,
2019-07-28] 200 2, Many thanks to [user:KAN,2019-07-28] for running the mirror,
[user:MikeMirzayanov,2019-07-28] for
41.
Helvetic Coding Contest 2019 online mirror **UPDATE: the editorial is [here](https://assets.codeforces.com/files/helvetic/helvetic-coding-contest-2019-editorial.pdf)**
**[Link to the online mirror](https://codeforces.me/contest/1184)**
Hello CodeForces! This year again, I'd like to invite you to [the online mirror](https://codeforces.me/contest/1184) of an open championship of Switzerland called HC2 (the Helvetic Coding Contest). A mirror was also held [one](http://codeforces.me/contest/958), [two](http://codeforces.me/contest/802) and [three years ago](http://codeforces.me/contest/690).
[The Helvetic Coding Contest](http://hc2.ch/) is a yearly contest held at [the EPFL](http://epfl.ch/) in Lausanne by the [PolyProg](http://polyprog.epfl.ch/) association. The contest itself took place on April the 13th, but the online mirror is scheduled on [**Sunday, 7th of July, 10:05 Moscow time**](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Helvetic+Codin...
Helvetic Coding Contest 2019 online mirror, , -contest-2019-editorial.pdf)**, /helvetic-coding-contest-2019-editorial.pdf) ------------------ Also:, 1. 大象大象你的鼻子为什么那么长 (solved all 14 problems!): [user:FizzyDavid,2019-07-07],
[user:300iq,2019-07-07, 2. zxtxdy (13 problems): [user:cuizhuyefei,2019-07-07], [user:MarkF,2019
-07-07], [user:zx2003,2019, 3. helveticow (12 problems): [user:scott_wu,2019-07-07],
[user:ksun48,2019-07-07], [user:ecnerwala, Acknowledgments: the problems were set by [user:bgamlath,2019-07-03],
[user:DamianS,2019-07-03
42.
Background of Good Bye 2019 Hi there! The recent Good Bye 2019 was very important event for us, and thanks for all the positive feedback we got, especially from [user:Radewoosh,2020-01-01]! As a follow-up, we would like to share some background on its preparation.
### **Problems:**
**A**: This one was the hardest to come up with. We wanted it to be super easy but still to include some idea, and this is like the $10$th version of the problem.
**B**: Initially there was another problem at this position. However, it turned out to be too hard for B (one orange couldn’t do it during the testing), and people didn’t like it in general, so we came up with another task.
**C**: Funny, but we didn’t know that it’s always possible to make array good with adding at most $1$ element before the contest.
**D**: This problem was created just 3 days before the contest to make it more balanced :O. We are glad that the contest did turn out to be well-balanced.
**E**: Initially we wanted this problem to be at positi...
Background of Good Bye 2019, Hi there! The recent Good Bye 2019 was very important event for us, and thanks
for all the positive
43.
Codeforces Round 975 (Div. 1, Div. 2) Ciao, Codeforces! We're glad to invite you to take part in [contest:2018] and [contest:2019], which will start on [contest_time:2018]. You will be given **6 problems** and **2 hours and 30 minutes** to solve them in both divisions. Some problems will be divided into subtasks.
**UPD: the time has been changed to [contest_time:2018], which is different from the time announced before. Please note the unusual starting time.**
This round is based on [Italian Olympiad in Informatics (OII) 2024](https://codeforces.me/blog/entry/133905).
The problems were authored by [user:lorenzoferrari,2024-09-22], [user:wksni,2024-09-22] and me.
We would like to thank
- [user:KAN,2024-09-22] for his nutella coordination;
- [user:Alexdat2000,2024-09-27] for Russian translation;
- [user:bortoz,2024-09-22], [user:collodel,2024-09-22], [user:dp_1,2024-09-22], [user:franfill,2024-09-22], [user:franv,2024-09-22], [user:harniver,2024-09-22], [user:jamesbamber,2024-09-22], [user:Kaey,2024-09-22], ...
Ciao, Codeforces! We're glad to invite you to take part in [contest:2018] and
[contest:2019], which
44.
Codeforces Round #538 (Div. 2) **TREMBLE BEFORE THE MIGHTY OMEGALULGRAPE**
Hello Codeforces!
We are honored to invite you to Codeforces Round #538 (Div. 2), which will take place at [contest_time:1114]. The round will be rated for all Division 2 participants **(with rating less than 2100)**. Still, we warmly welcome Division 1 participants to join us out of competition.
You will be given **6** problems to solve in **2 hours.** The round's problems were initially prepared by Duy-Bach ~Akikaze,2019-02-05 Le, Xuan-Tung ~neko_nyaa,2019-02-05 Nguyen and Xuan-Quang ~xuanquang1999,2019-02-05 D. Nguyen.
**There will be an interactive problem in this round.** Learn more about interactive problems [here](https://codeforces.me/blog/entry/45307).
This is our first attempt in making a Codeforces round, so suggestions are much welcome to help us improve ourselves. ;)
We also want to thanks many friends for making this round possible:
- Dmitry ~_kun_,2019-02-05 Sayutin...
1. [user:Hazyknight,2019-02-10] 2. [user:tfg,2019-02-10] 3.
[user:tempura0224,2019-02-10] 4, 1. [user:xlk200,2019-02-10] 2. [user:vasilescu_mihai,2019-02-10] 3.
[user:Cinro_9baka,2019-02-10
45.
Codeforces Round #694 (Div.1, Div.2) Hello Codeforces!
Сейчас проходит зимняя смена ЛКШ (Летней Компьютерной Школы), и мы в составе параллели A+A0 и её преподавателей подготовили полноценный Codeforces Round. Вы можете ознакомиться с предыдущими раундами, подготовленными учениками ЛКШ: [Codeforces Round #612](https://codeforces.me/contests/1286,1287), [Codeforces Round #530](https://codeforces.me/contests/1098,1099).
[Codeforces Round #694](https://codeforces.me/contests/1470,1471) начнётся во [contest_time:1470]. В обоих редакциях раунда Вам будет предложено по $6$ задач на $2$ часа. Раунд будет рейтинговым для обоих дивизионов.
Задачи раунда были придуманы и подготовлены [user:AliceG,2019-03-03], [user:Pakhomovee,2020-05-01], [user:MadProgrammer,2020-07-30], [user:ArtNext,2019-12-14], [user:fastmath,2019-09-28], [user:IgorI,2017-12-28], [user:Kapt,2018-10-11], [user:KhB,2019-10-26], [user:Helloo_zk,2020-03-01], [user:ipamaro,2018-12-30], [user:Arbuzniy_kekich,2020-02-17], [user:Mangooste,2020-02-17], [user:p...
Problems are authored and prepared by [user:AliceG,2019-03-03],
[user:Pakhomovee,2020-05-01, Задачи раунда были придуманы и подготовлены [user:AliceG,2019-03-03],
[user:Pakhomovee,2020-05-01
46.
Links of ICPC/CCPC Contests from China **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 Pro...
### 2019:
47.
April Fools Day Contest 2024 Hello, <s>April Fools lovers</s> Codeforces!
We, [user:AlperenT,2024-03-26], [user:flamestorm,2024-03-26], [user:toxicpie9,2024-03-26], and [user:willy108,2024-03-26], would like to invite everyone on Codeforces to [contest:1952]! The 12th April Fools Day Contest will take place on [contest_time:1952]. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
In this round, you will be given $n$ cool bugaboos where $-1 \le n \le \textbf{[REDACTED]}$ and **2** hours to solve them. The contest will use extended ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them). You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise.
Please note that the round is **unrated** and that the penalty for a **wrong submission** is **10** minutes.
To get an idea of what the contest will look like, you can check out the contests of the pas...
://codeforces.com/contest/784), [2018](https://codeforces.me/contest/952), [
2019](https://codeforces.com
48.
ROI 2018 in GYM Hi.
On Wednesday at [9:05 CET / 8:05 UCT](https://www.timeanddate.com/worldclock/fixedtime.html?day=27&month=3&year=2019&hour=11&min=5&sec=0&p1=166) you can participate in the GYM version of the finals of 2017-2018 Russian Olympiad in Informatics (ROI), Day 1.
And on Thursday there will be day 2, same time.
Links to GYM contets: [day1](https://codeforces.me/gym/102147) and [day2](https://codeforces.me/gym/102154).
5 hours, 4 problems, IOI-style scoring with subtasks.
Statements will be available in three languages: English, Russian, Polish.
We wanted to use those problems in a camp in Warsaw so we had to import the problems to some system anyway.
Then why not Polygon+Codeforces and thus allowing everybody to participate?
Huge thanks to [user:MikeMirzayanov,2019-03-25] for helping me with using GYM.
And credits to problem authors: [user:Andreikkaa,2019-05-21] for Radium, [user:Endagorion,2019-05-21] for Viruses, [user:pashka,2019-05-21] for Innophone, Георгий Корнее...
And credits to problem authors: [user:Andreikkaa,2019-05-21] for Radium,
[user:Endagorion,2019-05, Second day authors: [user:_kun_,2019-05-21] for Decryption, "jury" for Quick
Sort, [user:GlebsHP
49.
List of All Open Cup Contests Open Cup has very high quality problems. I made a list for all the contests containing the standings, sources, upsolving links, statements and discuss blog in codeforces. Some materials and links of old opencup contests are missing, maybe [user:snarknews,2020-11-10] could help to fill these entries.
I will update the list when new opencup stages published.
Note: most of the upsolving links need the logins for yandex.contest or opentrains.
## XXI Open Cup named after E.V. Pankratiev
| # | Contest | Upsolving | Materials |
|:--:|:------------|:--:|:--:|
| Stage 1 | [Grand Prix of Eurasia](https://official.contest.yandex.ru/opencupXXI/contest/20063/standings)<br/> [XXI All-Siberian Programming Contest. Online](https://olympic.nsu.ru/files/inet_res_2020_0.pdf) | [baekjoon](https://www.acmicpc.net/category/detail/2403)<br/> [yandex](http://official.contest.yandex.ru/opencupXXI/contest/20063) | [statement](https://yadi.sk/i/dsRvTxbgJ9fDXw) [discuss](https://codeforces.me/blog/...
Summer 2019. Day 2: 300iq Contest
2](http://karelia.snarknews.info/index.cgi?data=macros/day&sbname, &ncup=ocj)
[Petrozavodsk Winter 2019. Day 5: Gennady Korotkevich Contest 4](http
50.
Codeforces Round #601 Hello Codeforces!
I am glad to invite you to [Codeforces Round #601](https://codeforces.me/contests/1254,1255), which will take place on [contest_time:1254]. The round will be rated for both divisions.
All problems in this round were created and prepared by a team of all-Vietnamese setters: [user:MofK,2019-11-18], [user:Prof.PVH,2019-11-18], [user:UncleGrandpa925,2019-11-18], [user:ngk,2019-11-18]. This is the first Vietnamese Div1 round. We tried to make both the problems and the statements interesting and hope that you will enjoy them!
There is an interactive problem in the round. You can read the guide for interactive problem [here](https://codeforces.me/blog/entry/45307).
We would like to give a lot of thanks to:
- [user:MikeMirzayanov,2019-11-18] for the amazing platforms Codeforces and Polygon.
- [user:arsijo,2019-11-18] for excellent coordination and many valuable advice for the round.
- Our team of testers: [user:MikeMirzayanov,2019-11-18], [user:KAN,20...
- Our team of testers: [user:MikeMirzayanov,2019-11-18], [user:KAN,2019-11-18, : [user:MofK,2019-11-18], [user:Prof.PVH,2019-11-18],
[user:UncleGrandpa925,2019-11-18], [user:ngk
51.
Репетитор по спортивному программированию – помогите мне исполнить мечту Всем привет!
Меня зовут Александр Мокин. Последние три года в качестве основной работы я преподаю спортивное программирование.
Я был победителем Всероссийской олмипиады по информатике в 2012, призёром – в 2011 и 2013. В 2018 я стал финалистом чемпионата по программированию ICPC.
В 2019 я начал преподавать и помог десяткам людей продвинуться и достичь своих целей ([смотри отзывы](https://profi.ru/profile/MokinAB/)). За это время я разработал свой подход. Я не только провожу людей по пресловутым алгоритмам, но и учу конкретным техникам для решения реальных задач, а также быстро писать работающий код.
Теперь я хочу выйти на другой уровень. Я обращаюсь к мировой аудитории: не стесняйтесь писать мне в [Facebook](https://www.facebook.com/rembocoder/), [Telegram](https://t.me/rembocoder), личные сообщения или на е-мэйл: [[email protected]](mailto:[email protected]). Базовая цена: **$50/ч**.
Если я получу достаточно фидбэка, я обещаю создать YouTube-канал, посвящённый СП, ...
In 2019 I started teaching and have helped dozens of people to make progress
and reach their goals, В 2019 я начал преподавать и помог десяткам людей продвинуться и достичь своих
целей ([смотри
52.
Codeforces Round #879 (Div. 2, по Всероссийской олимпиаде имени Келдыша) [Рейтинговый] Всем привет!
В воскресенье состоится всероссийская олимпиада школьников для 5-8 классов имени Келдыша. Удачи всем участникам! Олимпиаду подготовила Московская методическая комиссия, известная вам также по Открытой олимпиаде школьников по программированию, Московской олимпиаде школьников по программированию, Московской командной олимпиаде и олимпиаде Мегаполисов (раунды <a href="https://codeforces.me/blog/entry/21185">327</a>, <a href="https://codeforces.me/blog/entry/23309">342</a>, <a href="https://codeforces.me/blog/entry/43615">345</a>, <a href="https://codeforces.me/blog/entry/47769">376</a>, <a href="https://codeforces.me/blog/entry/50613">401</a>, <a href="https://codeforces.me/blog/entry/54350">433</a>, <a href="https://codeforces.me/blog/entry/55201">441</a>, <a href="https://codeforces.me/blog/entry/57981">466</a>, <a href="https://codeforces.me/blog/entry/58229">469</a>, <a href="https://codeforces.me/blog/entry/61638">507</a>, <a href="https://codeforces.me/blo...
[user:MikeMirzayanov,2019-10-18] for systems Codeforces and Polygon, which was
used to prepare problems of this, Спасибо [user:Artyom123,2023-06-16] за координацию раунда, а так же
[user:MikeMirzayanov,2019-10-18
53.
April Fools Day Contest 2026 Hello, Codefoolers!
We, [user:AlperenT,2026-03-29], [user:Ari,2026-03-29], [user:ToxicPie9,2026-03-29], [user:flamestorm,2026-03-29], [user:prvocislo,2026-03-29], [user:temporary1,2026-03-29], and [user:willy108,2026-03-29] would like to invite everyone on Codeforces to [contest:2214]! The 14th April Fools Day Contest will take place on [contest_time:2214]. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
In this round, you will be given $n$ problems where $n$ is the number of different AI models I used today and **2** hours to solve them. The contest will use extended ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them). You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise.
There will be at least one non-interactive problem. In case you do not care about those problems, [here](https://codeforces.me/blog/e...
://codeforces.com/contest/784), [2018](https://codeforces.me/contest/952), [
2019](https://codeforces.com
54.
About Problemsetting (for AtCoder and Codeforces) Since the amount of information available about the preparation of a competitive programming contest for AtCoder/Codeforces is very little, I decided to collect here what was my experience.
I will try to both describe my experiences and give some general advice to wannabe problemsetters.
I hope that this will be useful to future problemsetters who are "out of the loop". Moreover, participants might be curious to know what happens behind the scenes (and maybe the platforms may consider this as a form of constructive feedback).
*Acronyms*:
- AGC = Atcoder Grand Contest
- GR = Codeforces Global Round
### Why I know something about problemsetting?
I am in the competitive programming world since ~8 years: I have participated in IOI/ICPC/GCJ and a number of contests on AtCoder/Codeforces (and lately Codechef).
I am not a top participant but, being in this world for so long, I know, more or less, all the standard tricks.
Recently, I was the author of the *flagship conte...
I had chosen as coordinator because I really liked Goodbye 2019) asking
whether I could be the
55.
Are subtasks evil? Everything in this blog is only my opinion, motivated by the recent round. If you disagree with it, let's discuss in the comments!
It's always hard to prepare a balanced problem set, and when the contest turns out to be unbalanced, an army of angry coders will destroy you in the comments section. But how can setters make Codeforces contests balanced?
Before, authors usually had to spend more time coming up with new problems which would close a too large gap between some $2$ problems. But now we have an easier solution! Any time there is a big difficulty gap in a contest, add subtasks to it!
[View](https://codeforces.me/blog/entry/67810?#comment-520212) on subtasks by [user:MikeMirzayanov,2019-11-24]:
Subtasks became really widely used in Codeforces contests recently. I looked at last $30$ contests rated for Div1 users. In turns out that:
Rounds $30 - 21$ had only $1$ subtasks in total,
Rounds $20 - 11$ had $3$ subtasks in total,
The last $10$ rounds already had $7...
,2019-11-24]:
56.
Codeforces Round #539 (Div. 1, Div. 2) Доброго времени суток, Codeforces!
Представляю вашему вниманию [Codeforces Round #539](https://codeforces.me/contests/1109,1113), который пройдет в эту [субботу, 16 февраля 2019 г. в 19:35](https://www.timeanddate.com/worldclock/fixedtime.html?day=16&month=2&year=2019&hour=19&min=35&sec=0&p1=166). Раунд будет **рейтинговым** для обоих дивизионов.
Авторы задач: [user:markysha,2019-02-14], [user:xolm,2019-02-14], [user:aleex,2019-02-14]. Это наш первый раунд на Codeforces, и, надеюсь, не последний :)
Выражаем благодарность всем кто помог в подготовке задач:
- Нашему координатору [user:arsijo,2019-02-14] за помощь во всем
- Большое спасибо [user:kefaa2,2019-02-14], [user:GandalfTheGrey,2019-02-14], [user:sharepoLOVEDDD,2019-02-14], [user:austrian_artist,2019-02-14], [user:Adalbert,2019-02-14], [user:StasyaCat,2019-02-14], [user:Fekete,2019-02-14] и [user:Daryusz,2019-02-14] за прорешивание задач (да, да к тестированию мы подошли основательно :))
- [user:gepardo,2019-02...
**Div 1:** 1. [user:Um_nik,2019-02-16] 2. [user:wxhtxdy,2019-02-16] (was so
close, **Div 1:** 1. [user:Um_nik,2019-02-16] 2. [user:wxhtxdy,2019-02-16] (это было
очень, - Our coordinator [user:arsijo,2019-02-14] for his help with everything -
Thanks very much, - Нашему координатору [user:arsijo,2019-02-14] за помощь во всем - Большое
спасибо, . [user:revivedDevil,2019-02-16] 4. [user:miseri,2019-02-16] 5. [user:fragusbot,
2019-02-16], /contests/1109,1113), that will take place at [Saturday, February 16, 2019 at
19:35](https, ://codeforces.com/contests/1109,1113), который пройдет в эту [субботу, 16
февраля2019 г. в 19:35](https, Авторы задач: [user:markysha,2019-02-14], [user:xolm,2019-02-14], [user:aleex,
2019-02-14]. Это наш
57.
My own algorithm — offline incremental strongly connected components in O(m*log(m)) Hello Codeforces!
As all of you know, there are so many known algorithms named after people who invented them — from the easiest ones, like Dijkstra, to the harder ones, like Berlekamp–Massey algorithm. These algorithms were innovative when they were invented, so of course, it's good that they are named after their inventors.
But, today, I've seen a blog about the solution to the problem "compute LCS of two strings in time $O((n + k) \cdot \log(k))$, where $n$ is the sum of lengths of the strings, and $k$ is the number of pairs of matching positions in them". To be honest, it a bit pissed me off that even this algorithm is named after its creators. Is it ok to name the solution to every possible problem after its author? I won't judge it. Anyway, I want my very own Radecki algorithm, so let me give it a try. If anyone has ever heard about it — it's cool. Let me know, and it'll be just another helpful blog on Codeforces.
Let's imagine the following problem: there is...
place between 2018 and 2019, which tells that this problem was created in
2018. Even if the intended
58.
Codeforces Round #546 (Div.2) Привет, Codeforces!
Я рад пригласить всех на раунд #546 Codeforces, который состоится послезавтра, [в понедельник, 11 марта 2019 г. в 19:35](https://www.timeanddate.com/worldclock/fixedtime.html?day=11&month=3&year=2019&hour=19&min=35&sec=0&p1=166). Раунд будет рейтинговым для всех участников из второго дивизиона (то есть для участников с рейтингом **меньше, чем 2100**). Как обычно, мы будем очень рады видеть всех участников из первого дивизиона на нашем контесте вне конкурса!
Это первый контест от нашего проекта "Обсуждаем задачи". Если у вас есть интересные задачи, то присылайте их нам, и, если они окажутся хорошими, вскоре мы дадим их на аналогичный раунд (возможно, и Div1). Вот ссылка на [программный пост](https://codeforces.me/blog/entry/65110).
Свои задачи на раунд предложили Фёдор [user:osaaateiasavtnl.,2019-03-09] Ушаков, Степан [user:IbragiMMamilov,2019-03-09] Стёпкин, Алексей [user:usertab34,2019-03-09] Розе, Денис [user:Denisson,2019-03-09] Шпаковский и Александр [...
Problems for the round have been proposed by Fedor [user:osaaateiasavtnl.,2019
-03-09] Ushakov, The round have been prepared by us, Dmitry [user:DmitryGrigorev,2019-03-09]
Grigoryev, Fedor, Раунд готовили мы, Дмитрий [user:DmitryGrigorev,2019-03-09] Григорьев, Фёдор
[user:osaaateiasavtnl, Свои задачи на раунд предложили Фёдор [user:osaaateiasavtnl.,2019-03-09]
Ушаков, Степан
59.
Most annoying person on CF It is this time of year! Many people trying to summarize all the things happened during the year. And since I love to hate people, I want to make a vote for most annoying person on CF in 2018.
I know that I'm in top contributors list for too long, so to vote for given person you should **downvote** the comment with this person's handle(s). Due to the nature of voting through comments on CF, you can vote for many people, and you can also upvote comments if you find given person's comments helpful/funny/positive.
If you care for your contribution but want to nominate a candidate, you can PM me their handle(s), then I will write a comment to vote. Note that I **will** write that it was you who nominated this person, so it saves your contribution but not relationships with the nominee. I will ignore messages from people without rating.
If you hate someone already nominated so much that you want them to know, you can also PM me so I'll add you to list of people who nominated given ...
Here are our champions: -515 [user:Numb,2019-01-01] -316 [user:riela,2019
-01-01] -264
60.
Story about edge coloring of graph You are given a graph $G$, and for each vertex $v$ you have to assign a positive integer **color** such that every adjacent pair of vertices (vertices directly connected by edge) have different color assigned. You have to minimize the maximum color assigned: In other words, you have to minimize the number of distinct assigned colors.
But that's [graph coloring](https://en.wikipedia.org/wiki/Graph_coloring) (vertex coloring). It's hard. Ok, one more time:
You are given a graph $G$, and for each **edge** $e$ you have to assign a positive integer **color** such that every adjacent pair of edges (edges sharing same endpoints) have different color assigned. You have to minimize the maximum color assigned: In other words, you have to minimize the number of distinct assigned colors.
This is the edge coloring of graph, and I will talk about this now.
*Note that this can be interpreted as "graph coloring (vertex coloring) of line graphs". In that sense, you can consider in a similar...
2019/2020 GP of Wroclaw G:
Choreography](https://codeforces.me/blog/entry/75266) * [Codeforces
61.
Codeforces Global Round 1 Добрый день!
Уже завтра, в [contest_time:1110] состоится [contest:1110].
Это первый раунд из новой серии [Codeforces Global Rounds](/blog/entry/65002). В раундах могут участвовать все, рейтинг тоже будет пересчитан для всех.
Призы в этом раунде:
- 30 лучших участников получат футболки.
- 20 футболок будут разыграны случайным образом среди участников с 31-го по 500-е место.
Призы в серии из 6 раундов в 2019 году:
- За каждый раунд лучшим 100 участникам начисляются баллы согласно [таблице](https://pastebin.com/QT5sXEaT).
- Итоговый результат участника равны сумме баллов для четырех лучших выступлений этого участника.
- Лучшие 20 участников по итоговым результатам получают толстовки и сертификаты с указанием места.
Задачи для этого раунда были разработаны целым коллективом авторов: [user:aitch,2019-02-06], [user:simonlindholm,2019-02-06], [user:grphil,2019-02-06], [user:V--gLaSsH0ldEr593--V,2019-02-06], [user:GreenGrape,2019-02-06], [user:Nebuchadnezzar,2019-02-06]...
The problems of this round were developed by a team of authors: [user:aitch,2019
-02-06, Задачи для этого раунда были разработаны целым коллективом авторов: [user:aitch,
2019-02-06
62.
Codeforces Round #584 (Dasha Code Championship Elimination Round) (div. 1 + div. 2) Hey, hi, hello.
[contest:1209] starts on [contest_time:1209] and lasts 2h30m. The score drain will be adjusted for longer contest duration.
It's a combined rated round with around eight problems. It is open and it is rated for everybody. Yes, it's rated.
There are Dasha t-shirts for top 30 competitors (not counting later-to-be onsite finalists).
As an extra, this is an elimination round for those who live in/near SPb/Novosibirsk.
More info about the championship is in the other [blog](https://codeforces.me/blog/entry/69530).
Thanks to Dasha.AI for making such an event for the community!
Problems are prepared by [user:MikeMirzayanov,2019-09-14], [user:FieryPhoenix,2019-09-14], [user:dragonslayerintraining,2019-09-14] and [user:Errichto,2019-09-14]. One of these setters also created Codeforces, thanks for that! And huge thanks to [user:_kun_,2019-09-14] for coordinating the round, to [user:Merkurev,2019-09-14], [user:isaf27,2019-09-14], [user:KAN,2019-09-14] and me for test...
1. [user:Petr,2019-09-14] 2. [user:wxhtxdy,2019-09-14] 3. [user:LayCurse,2019
-09-14] 4
63.
Testlib: tests + CI Hello, Codeforces.
I have wanted for a long time and now, finally, I sat down and did it.
Many of you are familiar with my [Testlib](https://github.com/MikeMirzayanov/testlib) project. This is a library that helps you develop problems if you are using C++.
In the case of problems for Codeforces rounds, its use is mandatory. It seems to me that it is almost a de facto standard for preparing materials for completely different olympiads and competitions.
The history of С++-Testlib is almost lost in centuries, I published the first version in 2005.
Nowadays, making edits to Testlib has become tricky. The code grown to thousands of lines, also it has too long a history.
This increases the likelihood of accidentally changing some aspect of behavior, which will jeopardize the holding of a Codeforces round or another important competition.
In short, making a bug in this code or changing behavior anywhere is highly discouraged.
So I recently took the plunge and wrote some test...
-2019, windows-server-2022), * different versions of different C++ compilers (g
++, clang ++, msvc
64.
Polygon updates (June-October 2019) Hello, Codeforces!
I and [user: cannor147,2019-11-07], as students of ITMO University, joined the Codeforces team in June. From June to October, we mainly dealt with the development of the Polygon platform. In this post, we would like to present to you a list of what we have done during this time. This list does not include minor bug fixes or any improvements that are invisible to users.
#### PIN codes for problems and contests
Sometimes very important contests and problems are being developed in Polygon. In such cases, a leader of the jury may be worried about data leaking. For example, it can be so because of the weak password of another member of the jury. PIN code is an additional factor of confirmation the access for the problem or contest and it can be set up only by the owner. It is assumed that the PIN code will be sent in another secure way.
There is a link Create Pin for the owners in the contest interface:
, Обновления Polygon (июнь-октябрь 2019)
Codeforces (c) Copyright 2010-2026 Михаил Мирзаянов
Соревнования по программированию 2.0
Время на сервере: 24.09.2026 12:40:48 (g2).
Десктопная версия, переключиться на мобильную.
При поддержке
