legends were competing there — [user:Petr,2020-12-31], [user:tomek,2020
-12-31], [user:ACRush,2020, ; [user:Petr,2020-12-31], [user:tomek,2020-12-31], [user:ACRush,2020-12-31],
then [user:tourist,2020-12-31
→ Pay attention
→ Top rated
| # | User | Rating |
|---|---|---|
| 1 | Benq | 3857 |
| 2 | jiangly | 3810 |
| 3 | maroonrk | 3534 |
| 4 | tourist | 3528 |
| 5 | Kevin114514 | 3510 |
| 6 | turmax | 3411 |
| 7 | Um_nik | 3387 |
| 8 | Radewoosh | 3367 |
| 9 | heuristica | 3322 |
| 10 | strapple | 3317 |
→ Top contributors
| # | User | Contrib. |
|---|---|---|
| 1 | Qingyu | 158 |
| 2 | maspy | 150 |
| 3 | Um_nik | 146 |
| 4 | Errichto | 139 |
| 5 | adamant | 136 |
| 6 | maroonrk | 134 |
| 7 | DNR | 133 |
| 8 | Dominater069 | 131 |
| 9 | Proof_by_QED | 130 |
| 9 | AmShZ | 130 |
→ Find user
→ Recent actions
You can use several words in query to find by all of them at the same time. In addition, if you are lucky search understands word forms and some synonyms. It supports search by title and author. Examples:
305— search for 305, most probably it will find blogs about the Round 305andrew stankevich contests— search for words "andrew", "stankevich" and "contests" at the same timeuser:mikemirzayanov title:testlib— search containing "testlib" in title by MikeMirzayanov"vk cup"— use quotes to find phrase as istitle:educational— search in title
Results
1.
Retiring from competitive competitive programming Recently, I feel I've passed my peak as a competitive programmer, and ran out of sufficient energy/motivation to keep the top form and be prepared to win the next contest.
I think I've done everything I can do as a competitive programmer, and now it's time to end my career as a professional (mind) sport player.
It was a great experience.
I'd like to thank everyone involved in the community, especially:
- Competitors. It was always nice to compete against you all!
- Problem writers who gave great problems to the community.
I started my career as a competitive math-puzzle solver in 1999.
The first contest was a local one named "junior sansu (arithmetic) olympiad".
Since then, I enjoyed this sport a lot for 21 years.
In 2007, I started TopCoder, and it changed my life.
The problems were great, and every single match of SRM felt like a once-in-a-life event.
A lot of legends were competing there — [user:Petr,2020-12-31], [user:tomek,2020-12-31], [user:ACRush,2020-12...
2.
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...
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:
Announcement of Codeforces Global Round 5
3.
О сорванном раунде 591/Технокубок 2020 — Отборочный Раунд 1 Привет, Codeforces!
К сожалению, недоброжелатели сорвали проведение раунда, сделав DDOS на нашу инфраструктуру. Ни координатор, ни авторы раунда не виноваты, что у вас не получилось полноценно принять участие в раунде. Пожалуйста, не минусуйте анонс раунда. Я думаю, что такая ситуация — дополнительный повод поддержать авторов. Они подготовили хорошие задачи!
Видимо, подобную атаку надо расценивать как симптом того, что Codeforces перерос фазу юношества и вступил во взрослую серьезную жизнь. Конечно, мы ответим адекватными мерами, чтобы защититься от подобных инцидентов. К счастью, за почти 10 лет работы вокруг сложилось большое сообщество тех, кому небезразличен Codeforces. Мы не переживаем по поводу возможных дополнительных трат или приложенных усилий. У нас всё получится. Раунды должны продолжаться.
— [user:MikeMirzayanov,2019-10-06]
**UPD 1:** Раунды будут нерейтинговыми, но по результатам тестирования лучшие участники отбора Технокубка будут приглашены в Фин...
About the Failed Round 591/Technocup 2020 — Elimination Round 1, О сорванном раунде 591/Технокубок 2020 — Отборочный Раунд 1, — [user:MikeMirzayanov,2019-10-06]
4.
Codeforces Global Round 9 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Hi!
On [contest_time:1375] we will host [contest:1375].
It is the third round of a 2020 series of [Codeforces Global Rounds](/blog/entry/65002). The rounds are open and rated for everybody.
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 2020:
- In each round top-100 participants get points according to the table.
- The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
- The best 20 participants over all series get sweatshirts and place certificates.
Thanks to XTX, which in 2020 supported the global rounds initiative!
The problems of this round were prepared by a team of authors: [user:adamant,2020-07-01], [user:anto...
- Our fantastic army of testers: [user:aryanc403,2020-07-01], [user:abhayps,2020
-07-01, - [user:MikeMirzayanov,2020-07-01] for the Codeforces and Polygon platforms., - [user:gamegame,2020-07-01] and [user:dorijanlendvaj,2020-07-01], for their
help in improving the, 1. [user:tourist,2020-07-04] 2. [user:scott_wu,2020-07-04] 3. [user:yosupo,2020
-07-04] 4, It is the third round of a 2020 series of [Codeforces Global
Rounds](/blog/entry/65002). The rounds, Thanks to XTX, which in 2020 supported the global rounds initiative!, The prizes for the 6-round series in 2020:, The problems of this round were prepared by a team of authors: [user:adamant,
2020-07-01
Announcement of Codeforces Global Round 9
5.
Codeforces Round #639 Hello, Codeforces!
I'm very glad to invite you to [contest:1344] and [contest:1345]. This contest will take place on [contest_time:1344]. In both divisions, you will have **2 hours 15 minutes** to solve **6 problems**. The score distribution will be announced closer to the start of the contest.
Of course, this round would not be possible without the help of many people, who I'd like to thank:
- [user:isaf27,2020-05-01], for coordinating this round, and helping with solution ideas.
- My ICPC teammates [user:Kuroni,2020-05-01] and [user:strongoier,2020-05-01], and coach [user:cn355,2020-05-01], for encouraging me to pursue competitive programming. In particular, I'd like to thank [user:Kuroni,2020-05-01] for being so spectacularly bad that a barely-orange user like myself actually has a place on our team.
- [user:300iq,2020-05-01], [user:antontrygubO_o,2020-05-01], [user:Ari,2020-05-01], [user:ffao,2020-05-01], [user:fpc_coder,2020-05-01], [user:gamegame,2020-05-01], [user:Kur...
ICPC teammates [user:Kuroni,2020-05-01] and [user:strongoier,2020-05-01], and
coach [user:cn355,2020-05, . - My ICPC teammates [user:Kuroni,2020-05-01] and [user:strongoier,2020
-05-01], and coach
Announcement of Codeforces Round 639 (Div. 1)
Announcement of Codeforces Round 639 (Div. 2)
6.
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!, go far, we will try to make your 2020 year more fun! I thank with all my heart
for the, try to achieve them! And do not go far, we will try to make your 2020 year
more fun!, — [user:MikeMirzayanov,2019-12-31]
7.
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
Announcement of Hello 2019
8.
Codeforces Round #639: the round is rescheduled Hello, Codeforces!
Unfortunately, I report that I decided to reschedule this round. I'm afraid that something might go wrong. Some strange database behavior has appeared, which leads to slow operation in completely unexpected places (it never was and should not be). I will work hard to fix it. My recent tests show that this can dramatically increase judging time (and leads to a huge queue). I don't want to risk the efforts of the writer, the coordinator, testers, and your time. Sorry about it, I was trying to fix it for many hours but I need more time. Hope it will be a great round!
Mike.
**UPD 1:** I temporarily rescheduled it on May, 6. But I'll discuss the date with the writer and coordinator and reschedule it again to the date they want.
**UPD 2:** [user:Monogon,2020-05-04] approved that [contest_time:1345] is good new date and time for the round. See you in 3 days!
**UPD 3:** It seems I've fixed the issue. It turned that it was connected with [week ago incident](htt...
and coordinator and reschedule it again to the date they want. **UPD 2:**
[user:Monogon,2020-05-04, **UPD 2:** [user:Monogon,2020-05-04] approved that [contest_time:1345] is good
new date and time
9.
Codeforces EDU: β-testing (Now in English!) <img src="/predownloaded/47/86/4786c2ec901c0b5b490794ca6fd5145f0dcdeae3.png" style="float:right; width: 400px; margin: 0 1em 1em 1em"/>
Hello Codeforces!
In February, in the Russian-language interface, we announced a new educational subsection of the website. It's time to go international!
I am pleased to invite you to test the new section, which so far has the working title EDU. I hope that someday EDU will become a real educational hub for fans of programming competitions. It will be great to have in one place the collected educational content with text and video materials, with selected thematic problems.
At the moment, its functionality is still under development, and here is the current progress and <i>β</i>-testing preview. Write your comments and suggestions in the comments here.
<center style="margin:2.5em;">
<a href="/edu/courses" style="text-decoration:none; font-size:18px; background-color:#01579B; color:white; font-weight:bold; padding:0.5em 1em;">Go to EDU ...
([user:pashka,2020-06-29]) for preparing the first English lesson. Please
support [user:pashka,2020-06, first feedback from international users. Many thanks to Pavel Mavrin
([user:pashka,2020-06-29]) for
10.
Goodbye 2020. Hello 2021! <img src="/predownloaded/f4/1f/f41ff0beb745fb2f84a55d9f2cc451273efc6267.jpg" style="width:300px; float:right; margin: 0 1em 1em 1em"/>
Hello Codeforces!
This unusual and difficult 2020 has come to an end! What will the new year be like?
I wish all of us that we have the opportunity to meet in person so that the contests take place not only online.
I ask you to think of something important and good. Let this wish come true!
We have had a large number of rounds 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 2021!
I wish the participants victories over yourself (and over problems!) and development of your skills, interest and curiosity!
Hello, 2021!
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 onc...
Goodbye 2020. Hello 2021!, ; float:right; margin: 0 1em 1em 1em"/> Hello Codeforces! This unusual and
difficult2020 has come, This unusual and difficult 2020 has come to an end! What will the new year be
like? I wish all of, — [user:MikeMirzayanov,2020-12-31]
11.
Streams on Codeforces Hello everyone!
Today Codeforces got support for streams! Thanks [user:tourist,2020-10-21] for the great idea!
There are two popular platforms supported: Twitch and YouTube. The opportunity to add streams to Codeforces is open to red participants and by individual invitations for now. We possibly open this opportunity to more users later.
The idea is that streamers will be able to announce their streams to the Codeforces audience. To do this, you should add the stream to the site using a special section in your profile. Please, note that when adding a Twitch stream, you just need to specify the URL of your channel, and when adding a YouTube broadcast, its unique short link (URL like youtu.be/...)
Shortly before the start of the stream, a notification about the upcoming stream will appear in the sidebar on the right, which will be shown to all site visitors.
For example, right now there is a [user:Errichto,2020-10-21]'s stream announcement in the sidebar.
![Streams in ...
[user:tourist,2020-10-21] Короткевичу за отличную идею! Поддерживаются две
популярные платформы, For example, right now there is a [user:Errichto,2020-10-21]'s stream
announcement in the sidebar., Hello everyone! Today Codeforces got support for streams! Thanks [user:tourist,
2020-10-21] for, Today Codeforces got support for streams! Thanks [user:tourist,2020-10-21] for
the great idea!, Например, прямо сейчас в русскоязычном интерфейсе есть анонс лекции Павла
[user:pashka,2020-10-21, Сегодня на Codeforces появилась поддержка трансляций (стримов)! Спасибо
Геннадию [user:tourist,2020
12.
Codeforces Round #635 _Riichi...Tsumo! 2 han 2000 points!_
Hi! Have you ever heard of the game called _Mahjong Soul_? It is a Japanese Mahjong game that is famous for the adorable characters.
We are excited to invite you to take part in [Codeforces Round #635](https://codeforces.me/contests/1336,1337), where you can help the characters in trouble. This round will be held on [contest_time:1336]. Most importantly, it is **rated** for both divisions!
Each division will be given **6 problems** and you will have **2.5 hours** to solve them. An interactive problem may be found in this round. If you are not familiar with interactive problems, you can learn about them [here](https://codeforces.me/blog/entry/45307).
The problems were prepared by [user:EternalAlexander,2020-04-14], [user:ustze,2020-04-14] and me [user:Sooke,2020-04-14].
We sincerely thank [user:isaf27,2020-04-14] for reviewing and coordinating the round, and ...
[user:MikeMirzayanov,2020-04-14] for providing such a great contest preparing
environment., were prepared by [user:EternalAlexander,2020-04-14], [user:ustze,2020-04-14]
and me [user:Sooke,2020, - Div.1 1. [user:boboniu,2020-04-15] (First to solve 1E!) 2. [user:maroonrk,2020
-04-15] (First to, - Div.2 1. [user:Bojangles,2020-04-15] (First to solve 2E!) 2.
[user:JbopkynyRubkLuxSR,2020-04-15, - [user:300iq,2020-04-14], [user:HIR180,2020-04-15], [user:gisp_zjz,2020
-04-15], [user:CMXRYNP,2020, - [user:ouuan,2020-04-14], [user:QAQAutomaton,2020-04-14], [user:PinkRabbit,2020
-04-14, The problems were prepared by [user:EternalAlexander,2020-04-14], [user:ustze,
2020-04-14] and me
Announcement of Codeforces Round 635 (Div. 1)
Announcement of Codeforces Round 635 (Div. 2)
13.
Codeforces Round #658 Hello, Codeforces!
I'm very glad to invite you to [contest:1381] and [contest:1382]. This contest will take place on [contest_time:1381]. In both divisions, you will have **2 hours** to solve **5 problems** (and one subtask). The score distribution will be announced closer to the start of the round.
Huge thanks to:
- [user:isaf27,2020-07-19] for excellent coordination of this round
- [user:Andreii,2020-07-19], [user:antontrygubO_o,2020-07-19], [user:Ari,2020-07-19], [user:DeadlyCritic,2020-07-19], [user:gamegame,2020-07-19], [user:growup974,2020-07-19], [user:hugopm,2020-07-19], [user:Kuroni,2020-07-19], [user:NooB_MB,2020-07-19], [user:Priyank,2020-07-19], [user:SecondThread,2020-07-19], [user:--Someone--,2020-07-19], [user:talibmohd,2020-07-19], [user:WNG,2020-07-19] for testing the problems and providing useful feedback.
- [user:MikeMirzayanov,2020-07-19] for providing Codeforces and Polygon platforms.
I've worked hard to ensure the pretests are short and the statement...
- [user:Andreii,2020-07-19], [user:antontrygubO_o,2020-07-19], [user:Ari,2020
-07-19], [user:DeadlyCritic, - [user:isaf27,2020-07-19] for excellent coordination of this round -
[user:Andreii,2020-07-19, 1. [user:Benq,2020-07-21], 1. [user:badger_champion,2020-07-21], 2. [user:Mai_madarchod_hu,2020-07-21], 2. [user:Um_nik,2020-07-21], 3. [user:KAN,2020-07-21], 3. [user:rulai,2020-07-21], 4. [user:Petr,2020-07-21], 4. [user:Vimmer,2020-07-21], 5. [user:niynip,2020-07-21]
Announcement of Codeforces Round 658 (Div. 1)
Announcement of Codeforces Round 658 (Div. 2)
14.
Codeforces Round #648 (Div. 2) Hi everyone!
I would like to invite you to my fifth Codeforces Round, that I set with my friends [user:FastestFinger,2020-06-05], [user:Vivek1998299,2020-06-05] and [user:ridbit10,2020-06-05].
We are excited to bring another contest within a week :D
With that said, I bring to your attention our new [contest:1365] that will take place on [contest_time:1365]. If your rating is less than **2100**, this round will be rated for you; otherwise, you can participate out of competition.
I would really like to thank:
- [user:FastestFinger,2020-06-05], [user:Vivek1998299,2020-06-05] and [user:ridbit10,2020-06-05] for helping with preparing problems and giving new ideas.
- [user:300iq,2020-06-05] for coordinating our round.
- [user:Um_nik,2020-06-06], [user:antontrygubO_o,2020-06-05], [user:ksun48,2020-06-05], [user:Jeel_Vaishnav,2020-06-05], [user:aryanc403,2020-06-05], [user:FlowerOfSorrow,2020-06-05], [user:KonaeAkira,2020-06-05], [user:_Aaryan_,2020-06-05], [user:Ari,2020-06-...
[user:FastestFinger,2020-06-05], [user:Vivek1998299,2020-06-05] and
[user:ridbit10,2020-06-05
Announcement of Codeforces Round 648 (Div. 2)
15.
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
Announcement of Good Bye 2019
16.
Codeforces Round #646 (Div. 2) Hi everyone!
I would like to invite you to my fourth Codeforces Round, which I have made with my friends [user:FastestFinger,2020-05-29] and [user:TheOneYouWant,2020-05-29]. In terms of problems, it is my favorite among all my rounds.
With that said, I bring to your attention our new [contest:1363] that will take place on [contest_time:1363]. If your rating is less than **2100**, this round will be rated for you; otherwise, you can participate out of competition.
I would really like to thank:
- [user:FastestFinger,2020-05-29] and [user:TheOneYouWant,2020-05-29] for helping with preparing problems and giving new ideas.
- [user:antontrygubO_o,2020-05-29] for coordinating our round
- [user:300iq,2020-05-29], [user:Jeel_Vaishnav,2020-05-29], [user:Ari,2020-05-29], [user:aryanc403,2020-05-29], [user:mahmoudbadawy,2020-05-29], [user:Vivek1998299,2020-05-29], [user:Uzumaki_Narutoo,2020-05-30], [user:Bakry_,2020-05-31], [user:smartnj,2020-05-30] and [user:Nikhil_Medam,2020-05-29]...
[user:FastestFinger,2020-05-29] and [user:TheOneYouWant,2020-05-29]. In terms
of problems, it is my, friends [user:FastestFinger,2020-05-29] and [user:TheOneYouWant,2020-05-29].
In terms of problems, - [user:FastestFinger,2020-05-29] and [user:TheOneYouWant,2020-05-29] for
helping with preparing
Announcement of Codeforces Round 646 (Div. 2)
17.
Codeforces Round #633 **내가 돌아왔다!** (Hello, Codeforces!)
I am thrilled to introduce you to [Codeforces Round #633](https://codeforces.me/contests/1338,1339). Followings are basic information:
- This contest will take place on [contest_time:1338].
- The round is **rated for all participants** who can understand this announcement. There will be two divisions.
- There are **5 problems** in each division and you will have **2 hours** to solve it.
- Score distribution will be announced later.
Followings are contributors:
- **Authors**: [user:McDic,2020-04-10] (All Div.2 problems and Div.1 D), [user:tzuyu_chou,2020-04-10] (Div.1 E)
- **Coordinator**: [user:antontrygubO_o,2020-04-10]
- **Testers**:
- **Phase 1** (When this round was supposed to be Div.2): [user:dorijanlendvaj,2020-04-10], [user:SoulTch,2020-04-10], [user:pajenegod,2020-04-10], [user:AryaPawn,2020-04-10], [user:Rahul,2020-04-10], [user:mcdx9524,2020-04-10], [user:300iq,2020-04-10], [user:Nemo,2020-04-10], [user:tfg,2020-04-10]...
[user:antontrygubO_o,2020-04-13] but excluded for some reasons. 1. **Binomial
Determinant** is old Div1D, contributors: - **Authors**: [user:McDic,2020-04-10] (All Div.2 problems and
Div.1 D, - **Authors**: [user:McDic,2020-04-10] (All Div.2 problems and Div.1 D),
[user:tzuyu_chou,2020-04, - [user:antontrygubO_o,2020-04-10] is the most intense coordinator I have ever
met. He rejected, 1. [user:Nachia,2020-04-12] 2. [user:Riviclia,2020-04-12] 3.
[user:0.142857,2020-04-12] 4, 1. [user:tourist,2020-04-12] 2. [user:Radewoosh,2020-04-12] 3. [user:tlwpdus,
2020-04-12] 4
Announcement of Codeforces Round 633 (Div. 1)
Announcement of Codeforces Round 633 (Div. 2)
18.
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, that 2022 is pronounced like "2020 too". Not that. I want a completely
different year! Anyway, we, Oh yes, 2021 ends! I recently realized that 2022 is pronounced like "2020 too".
Not that. I want a
19.
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
20.
Algorithms Thread 8: Tree Basics (+ Gym Contest) Algorithms Thread Episode 8: Tree Basics
==================
Episode 8 of Algorithms Thread [comes out in <90 minutes!](https://youtu.be/MOy4UDjN8DM) This one is a bit more beginner-friendly and covers the following ideas:
- Graph/Tree Diameters
- Binary Lifting
- Tree Flattening with Euler tours
Also, to make sure you have actually learned that stuff, I made a [custom Gym set on CodeForces](https://codeforces.me/gym/102694) that will last two weeks that hopefully is really good practice for making sure you have learned this stuff. Here is a link to the gym set; it will be available 45 minutes after the video comes out so that people have time to watch the video before starting the set, if they are interested in penalty points. All of the problems in the gym are original to this set (in their flavortext at least, some are simple enough that I'm sure they have appeared in other contests before).
The new gym integration was heavily inspired by [user:Errichto,2020-08-16]'s ...
other contests before). The new gym integration was heavily inspired by
[user:Errichto,2020-08-16]'s, The new gym integration was heavily inspired by [user:Errichto,2020-08-16]'s
Matrix Expo set format
Announcement of AlgorithmsThread Tree Basics Contest
21.
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
Announcement of Codeforces Round 589 (Div. 2)
22.
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
early2020 I
23.
AtCoder Library Recently, the number of algorithms and data structures we use in competitive programming are rapidly growing.
It's a nice thing: by using more algorithms, the variety of possible problems gets wider, and we can enjoy more problems.
On the other hand, before reaching adhoc, thinking-oriented part of this competition, we have to spend more and more time to learn algorithms.
Sometimes a problem asks matching on general graphs; you have to find a paper describing it, read it, and implement its really complicated algorithm. Or sometimes you have to spend time tuning your library by a constant factor. Or sometimes you use multiple pre-written codes together, the variable names collide, and get annoyed.
Until now, I basically rejected all problems that require pre-written codes of complicated algorithms because I don't like these things. For example, we never used segment trees with lazy propagation in our contests.
However this way we can't use otherwise interesting problems and it ...
interesting part of problems. All the codes were implemented by [user:yosupo,
2020-09-07], and testings, will keep the "easy implementation" rule in the future — the next admin
[user:maroonrk,2020-09-07, All the codes were implemented by [user:yosupo,2020-09-07], and testings were
done by
24.
Good Bye 2020 Hello Codeforces!
We have a pleasure to invite you to [Good Bye 2020](https://codeforces.me/contests/1466), which will take place on [contest_time:1466]. You will have **3 hours** to solve **9 problems**. The round will be rated for participants of both divisions.
The problems for this round were prepared by [user:gawry,2020-12-28], [user:Anadi,2020-12-28] and me.
We would like to thank everyone who made this round possible:
- [user:Nebuchadnezzar,2020-12-28] and [user:KAN,2020-12-28] for the excellent coordination;
- [user:H4CKOM,2020-12-28], [user:221,2020-12-28], [user:manikjain4,2020-12-28], [user:namanbansal013,2020-12-28], [user:Prabowo,2020-12-28], [user:saurabhshadow,2020-12-28], [user:Gauravvv,2020-12-28], [user:Fly_37,2020-12-28], [user:Thaid,2020-12-28], [user:__rkm__,2020-12-28], [user:6520,2020-12-28], [user:Himanshu_77,2020-12-28], [user:H_M_Vaghasiya,2020-12-28], [user:Jellyman102,2020-12-28], [user:SecondThread,2020-12-28], [user:Origenes,2020-12-28], [...
Good Bye 2020, - [user:H4CKOM,2020-12-28], [user:221,2020-12-28], [user:manikjain4,2020-12-28, - [user:MikeMirzayanov,2020-06-02] for great platforms Codeforces and Polygon., - [user:Nebuchadnezzar,2020-12-28] and [user:KAN,2020-12-28] for the excellent
coordination;, 1. [user:tourist,2020-12-30] 2. [user:maroonrk,2020-12-30] 3. [user:Benq,2020
-12-30] 4, The problems for this round were prepared by [user:gawry,2020-12-28],
[user:Anadi,2020-12-28] and
Announcement of Good Bye 2020
25.
Codeforces Global Round 8 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Hi!
On [contest_time:1368] we will host [contest:1368].
It is the second round of a 2020 series of [Codeforces Global Rounds](/blog/entry/65002). The rounds are open and rated for everybody.
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 2020:
- 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.
- The best 20 participants over all series get sweatshirts and place certificates.
Thanks to XTX, which in 2020 supported the global rounds initiative!
Problems for this round are set by me. Thanks a lot to the coordin...
-global-rounds-2020-18730990/) (courtesy of [user:aropan,2020-06-19])., 1. [user:ecnerwala,2020-06-19] 2. [user:tourist,2020-06-19] 3. [user:Marcin_smu,
2020-06-19] 4, It is the second round of a 2020 series of [Codeforces Global
Rounds](/blog/entry/65002). The, Problems for this round are set by me. Thanks a lot to the coordinator
[user:300iq,2020-06-17] and, Thanks to XTX, which in 2020 supported the global rounds initiative!, The prizes for the 6-round series in 2020:
Announcement of Codeforces Global Round 8
26.
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 ...
I think the author of this problem is [user:Endagorion,2020-04-23]., The intended solution is $O(n\log^2 n)$. This improved solution credits to
[user:_rqy,2020-04-23, The intended solution is $O(na^2 \log n)$. This solution credits to
[user:djq_cpp,2020-04-23]., This solution credits to [user:djq_cpp,2020-04-23]., [user:MiFaFaOvO,2020-04-23], #### Exp in Gennady Korotkevich Contest 5 By [user:tourist,2020-04-23], #### Rhyme By [user:Elegia,2020-04-23], ####Chinese Elephant Chess By [user:djq_cpp,2020-04-23], ####[Chain Reaction](http://uoj.ac/problem/50) in UOJ Round 3 By
[user:vfleaking,2020-04-23], ####[Pearl](https://loj.ac/problem/3120) in CTSC 2019 By [user:laofudasuan,2020
-04-23], . The following is the discussion with [user:tEMMIE.w.,2020-04-23]., Thank [user:Elegia,2020-04-23] and [user:djq_cpp,2020-04-23] for developing
this technique. Thank
27.
Codeforces Round #651 (Div. 2) Hi everyone!
I would like to invite you to another one of our rounds, that I set with my friends [user:FastestFinger,2020-06-05], [user:smartnj,2020-06-19], [user:the_hyp0cr1t3,2020-06-19] and [user:ridbit10,2020-06-05].
The round [contest:1370] will take place on [contest_time:1370]. If your rating is less than **2100**, this round will be rated for you; otherwise, you can participate out of competition.
I would really like to thank my co-setters and:
- [user:isaf27,2020-06-05] for coordinating our round.
- [user:cerberus97,2020-06-19], [user:Devil,2020-06-19], [user:Taran_1407,2020-06-19], [user:Alireza_Keshavarz,2020-06-19], [user:Vivek1998299,2020-06-19], [user:KonaeAkira,2020-06-19], [user:demoralizer,2020-06-19], [user:Dragnoid99,2020-06-19], [user:agtxdy,2020-06-19], [user:Rajdeep,2020-06-19], [user:aryanc403,2020-06-19], [user:lavish315,2020-06-19], [user:DeadlyCritic,2020-06-19], [user:Utkarsh.25dec,2020-06-19], [user:AmShZ,2020-06-19], [user:_Aaryan_,2020-06-19]...
[user:FastestFinger,2020-06-05], [user:smartnj,2020-06-19],
[user:the_hyp0cr1t3,2020-06-19] and, ,2020-06-19], [user:Taran_1407,2020-06-19], [user:Alireza_Keshavarz,2020-06-19
Announcement of Codeforces Round 651 (Div. 2)
28.
Codeforces Raif Round 1 [Div. 1 + Div. 2] Привет, Codeforces!
Присоединяйтесь к объединенному Div1 и Div2 раунду [contest:1428], который будет проходить при поддержке Райффайзенбанка и начнётся в [contest_time:1428]. **Он будет рейтинговым и открытым для обоих дивизионов. Обратите внимание на нестандартное время начала раунда.**
Все задачи были придуманы и подготовлены [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].
Спасибо:
- [user:isaf27,2019-05-10] и [user:KAN,2020-10-15] за коодинацию раунда и помощь в подготовке
- [user:zhangguangxuan99,2020-10-15] за то, что он лучший IOI тренер <3
- Армии наших тестеров: [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],...
time is unusual.** All problems were authored and prepared by [user:bensonlzl,
2020-10-15, задачи были придуманы и подготовлены [user:bensonlzl,2020-10-15],
[user:oolimry,2020-10-15, - Our army of testers: [user:Ari,2020-10-15], [user:KAN,2020-10-15],
[user:Monogon,2020-10-15, - [user:MikeMirzayanov,2019-05-10] for great systems Codeforces and Polygon., - [user:MikeMirzayanov,2019-05-10] за замечательные системы Codeforces и
Polygon., - [user:isaf27,2019-05-10] and [user:KAN,2020-10-15] for round coordination and
help with, - [user:isaf27,2019-05-10] и [user:KAN,2020-10-15] за коодинацию раунда и
помощь в подготовке, - Армии наших тестеров: [user:Ari,2020-10-15], [user:KAN,2020-10-15],
[user:Monogon,2020-10-15, 1. [user:Radewoosh,2020-10-17], 2. [user:Um_nik,2020-10-17], 4. [user:ecnerwala,2020-10-17], 5. [user:littlelittlehorse,2020-10-17], A: [user:300iq,2020-10-17], All problems were authored and prepared by [user:bensonlzl,2020-10-15],
[user:oolimry,2020-10-15, B: [user:icecuber,2020-10-17], C: [user:Not-Afraid,2020-10-17], D: [user:Radewoosh,2020-10-17], E: [user:errichto,2020-10-17], F: [user:fmota,2020-10-17], G: [user:Radewoosh,2020-10-17], H: [user:Radewoosh,2020-10-17], [user:Ari,2020-10-15] gato to:
Announcement of Codeforces Raif Round 1 (Div. 1 + Div. 2)
29.
Codeforces: Results of 2020 [list some changes and improvements] Hello, Codeforces!
I understand that 2021 has been going on for a long time, but here I have picked up a subset of some of the improvements that the Codeforces team made in 2020. Soon I will publish numbers (no, charts) with statistics for 2020. In the meantime, I bring to your attention a list of changes and improvements.
By the way, this is a decent list. This is about half to a quarter of all changes. It's just that other changes are more often somewhere in the internals of the system and are not visible to users. Please read this list. Each item is the effort of someone from the team. Thanks to [user:geranazavr555,2021-03-14], [user:kuviman,2021-03-14] and [user:cannor147,2021-03-14] for their efforts. You've made our platform better! Well, by the way, I don't quit programming and many improvements were made by me.
The items on the list are written in a concise and informal form, many of the items I just copied from commit messages from git. If you want more details &mdash...
Codeforces: Results of 2020 [list some changes and improvements], picked up a subset of some of the improvements that the Codeforces team made in
2020. Soon I will, problems the archive * Now Codeforces highlights recent changes in problem
statements * Nerc2020, some of the improvements that the Codeforces team made in 2020. Soon I will
publish numbers (no, charts
30.
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 ...
Технокубок 2020 — Отборочный Раунд 1 (и открытые рейтинговые раунды Codeforces
Round 591 Div.1, Div,
Авторы отборочного раунда — [user:BledDest,2019-10-06], [user:MikeMirzayanov,
2019-10-06
, href="http://codeforces.me/blog/entry/70187">Технокубок 2020. Раунд будет
длиться два часа, problems of Technocup 2020 Elimination Round 1 that will be held at the same
time. Technocup is a, приглашены на финал Технокубка 2020 из этого раунда. Кроме этого, будет
проведен **четвертый** раунд., школьников Технокубок 2020 <http://codeforces.me/blog/entry/70187>. Раунд
будет длиться, The Elimination Round authors are [user:BledDest,2019-10-06],
[user:MikeMirzayanov,2019-10-06
Announcement of Technocup 2020 - Elimination Round 1
31.
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...
32.
Codeforces Round #638 (Div. 2) Hi Codeforces!
I’m thrilled to invite you to [contest:1348], which will take place on [contest_time:1348]. It's rated!
There will be **6 problems**, and you will have **2.5 hours** to solve them. All the problems are written and prepared by me.
Huge thank you to everyone who made this round possible:
- [user:adedalic,2020-04-28] for awesome coordination, guidance, advice, and more <3
- [user:dragonslayerintraining,2020-04-28] for extensive testing, feedback, and buffing tests
- [user:pikmike,2020-04-28], [user:walnutwaldo20,2020-04-28], [user:Benq,2020-04-28], [user:hocky,2020-04-28], [user:Geothermal,2020-04-28], [user:isaf27,2020-04-28], [user:McDic,2020-04-28], [user:bfs.07,2020-04-28], [user:iankury,2020-04-28], [user:songsinger,2020-04-28], [user:Agnimandur,2020-04-28], [user:dcshin,2020-04-28], [user:chrome,2020-04-28], [user:Rods,2020-04-29], [user:brian,2020-04-29], and [user:HAEtaRhoEta,2020-04-30] for taking the time to test and provide invaluable advice
...
round possible: - [user:adedalic,2020-04-28] for awesome coordination,
guidance, advice, and more <3, **UPD:** Thanks also to [user:darnley,2020-05-01] for proofreading statements
and suggestions!, - [user:MikeMirzayanov,2020-04-28] for wonderful platforms Codeforces and
Polygon (preparing, - [user:adedalic,2020-04-28] for awesome coordination, guidance, advice, and
more <3, - [user:dragonslayerintraining,2020-04-28] for extensive testing, feedback, and
buffing tests, - [user:pikmike,2020-04-28], [user:walnutwaldo20,2020-04-28], [user:Benq,2020
-04-28], [user:hocky, 1. [user:dreamoon_love_AA,2020-05-01], 2. [user:KrK,2020-05-01], 2. [user:czyarl,2020-05-01], 3. [user:NishimiyaShouko,2020-05-01], 4. [user:PureVessel,2020-05-01], 4. [user:antontrygubO_o,2020-05-01], 5. [user:I_love_Tanya_Romanova,2020-05-01], 5. [user:Neraxis,2020-05-01]
Announcement of Codeforces Round 638 (Div. 2)
33.
Codeforces Global Round 12 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
¡Buenos días! (That's Spanish for "what's up homies")
On [contest_time:1450] we will host [contest:1450].
It is the sixth round of a 2020 series of [Codeforces Global Rounds](/blog/entry/65002). The rounds are open and rated for everybody.
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 2020:
- In each round top-100 participants get points according to the table.
- The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
- The best 20 participants over all series get sweatshirts and place certificates.
Thanks to XTX, which in 2020 supported the global rounds initiative!
The problems were written and prepared by smart Cu...
[contest_time:1450] we will host [contest:1450]. It is the sixth round of a
2020 series of, - [user:Ernestico,2020-12-02], [user:McDic,2020-12-02], [user:Ari,2020-12-02],
[user:gamegame,2020, 1. [user:Benq,2020-12-06] 2. [user:tourist,2020-12-06] 3. [user:jiangly,2020
-12-06] 4, It is the sixth round of a 2020 series of [Codeforces Global
Rounds](/blog/entry/65002). The rounds, Thanks to XTX, which in 2020 supported the global rounds initiative!, The prizes for the 6-round series in 2020:, The problems were written and prepared by smart Cuban [user:Devil,2020-12-02]
and stupid Americans
Announcement of Codeforces Global Round 12
34.
Hello 2020 **새해 복 많이 받으세요, 코드포스!** (Happy new year, Codeforces!)
Welcome to the first Codeforces Round of the new decade, [Hello 2020](https://codeforces.me/contests/1284)! The round will be held on [Jan/04/2020 15:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=4&month=1&year=2020&hour=15&min=5&sec=0&p1=166).
Some information about the round:
* Div 1, 2 combined
* 2.5 hours!
* **7 problems!**
* No subtasks!
* Score distribution: 500-1250-1750-2500-2750-4000-4000
* Yes, it is rated!
This round is prepared by [user:ko_osaga,2020-01-01] [user:nong,2020-01-01] [user:ckw1140,2020-01-01]. I am personally very thrilled to deliver my first Codeforces contest as such a memorable one!
More credits for the contest:
* Coordinator: [user:300iq,2020-01-01]
* Testers: [user:kdh9949,2020-01-01] [user:kriii,2020-01-01] [user:OnionPringles,2020-01-01] [user:molamola.,2020-01-01] [user:evenharder,2020-01-01] [user:jihoon,2020-01-01] [user:DongwonShin,2020-01-01] [user:xia...
Hello 2020, * Coordinator: [user:300iq,2020-01-01] * Testers: [user:kdh9949,2020-01-01]
[user:kriii,2020-01-01, 1. [user:mnbvmar,2020-01-04] 2. [user:TLE,2020-01-04] 3. [user:Benq,2020-01-04]
4. [user:tourist, This round is prepared by [user:ko_osaga,2020-01-01] [user:nong,2020-01-01]
[user:ckw1140,2020-01
Announcement of Hello 2020
35.
Новое на Codeforces: возможность переписать условие в мэшапе Привет, Codeforces!
Есть кое-что новое. Кажется, теперь переиспользовать задачи с раундов в учебных и прочих целях станет проще.
Как вы знаете, <a href="https://codeforces.me/blog/entry/10099">в мэшапы</a> можно добавлять задачи с прошедших раундов Codeforces просто по их кодам вида <code>1234D</code> (айдишник контеста + буква задачи). Я сам регулярно этим пользовался, когда преподавал в Саратовском университете — очень удобно было так делать тренировки: задачи ожидаемой сложности и тематики, есть русское и английское условия, можно посмотреть разбор и множество решений. Почти всюду очень сильные тесты по причине поддержки взломов и довзламывания, задачи хорошо подготовлены. Кроме того, с помощью <a href="https://codeforces.me/blog/entry/21912">списков пользователей</a> можно для группы учащихся легко подобрать задачи, которые они не решали.
<img src="/predownloaded/ac/ae/acae3c9dda56f3fd7a480ec96ed717dd5ca18f49.png" style="float:right; margin: 0 1em 1em 1em; width:60...
просьб была от Daniel [user:Darooha,2020-11-19] Sleator
(https://en.wikipedia.org/wiki/Daniel_Sleator, . One of the most recent such requests was from Daniel [user:Darooha,2020
-11-19] Sleator (https
36.
Codeforces Round #663 (Div. 2) Henlo Codeforces! ^_^
I invite you to participate in [Codeforces Round #663 (Div.2)](https://codeforces.me/contests/1391) taking place on [contest_time:1391]. The round is rated for users rated less than 2100, while other users can participate non-competitively.
The round features five problems, and you have 2 hours to solve them. There may, or may not, be an interactive problem; regardless, you should [know](https://codeforces.me/blog/entry/45307) how to deal with them.
I would, now, like to thank–
- [user:antontrygubO_o,2020-07-31] for coordination <s>and manipulation</s>.
- [user:AwakeAnay,2020-07-31], [user:AsleepAdhyyan,2020-07-31], and [user:RestingRajarshi,2020-07-31] for always listening to my problem ideas.
- [user:BRCode,2020-08-03] for making [3b1b-style](https://www.youtube.com/watch?v=LYrtRnz35sU) video editorials of the problems!
- [user:Aggu_01000101,2020-08-07], [user:Devil,2020-07-31], [user:Dragnoid99,2020-07-31], [user:NOOBxCODER,2020-07-31], [use...
* [user:420iq,2020-08-10],
* [user:Heltion,2020-08-10] ,
* [user:LayCurse,2020-08-10],
* [user:PouyaNavid,2020-08-10],
* [user:risujiroh,2020-08-10],
* [user:silxi,2020-08-10] , , now, like to thank– - [user:antontrygubO_o,2020-07-31] for coordination and
manipulation, - [user:antontrygubO_o,2020-07-31] for coordination and manipulation. -
[user:AwakeAnay, Here are video editorials by [user:BRCode,2020-08-09]:
Announcement of Codeforces Round 663 (Div. 2)
37.
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...
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
38.
Support Anton Trygub Since [user:antontrygubO_o,2020-07-12] has became CF coordinator he is trying hard to make rounds which meet his standards for quality and (more importantly) beauty. I think he is doing a great job.
For some time there is a very vocal group of people who dislike his view on things. I feel like it will be hard for Anton to maintain his work if he would think that majority of people doesn't approve.
But I don't really think that this is a majority. If you enjoy rounds prepared or coordinated by Anton, please comment here with some positive feedback.
`#AdHocProblemsMatter`
Since [user:antontrygubO_o,2020-07-12] has became CF coordinator he is trying
hard to make rounds
39.
Problem Ratings are Recalculated [May, 2020] Hi!
As many have noticed, sometimes problem ratings were assigned in a strange way that was not consistent with expectations. For example, ratings for complex problems of Div3 rounds were often overestimated. This was mainly due to the fact that high-ranking unofficial participants did not try such problems. It turned out that despite the high rating of a participant, a problem is not solved by the participant, and this fact raised the rating of the problem. It is not entirely correct to take into account only official participants since ratings for difficult problems are sometimes more accurately determined by unofficial participants.
Somewhere in the comments, I've read that problem ratings are set manually. Of course, this is not so. The process is automated, but I start it manually (I will fix it somehow).
I changed the formulas for calculating problem ratings, now they slightly better correspond to expectations. New problem ratings are already available on the website. I ...
Problem Ratings are Recalculated [May, 2020]
40.
Codeforces Global Round 10 Hi! <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width: 200.0px;float: right;margin: 0 1.0em 1.0em 1.0em;max-width: 100.0%;max-height: 100.0%;">
On [contest_time:1392] we will host [contest:1392].
This is the fourth round of a 2020 series of [Codeforces Global Rounds](https://codeforces.me/blog/entry/65002). The rounds are open and rated for everybody.
The prizes for this round are as follows:
- The top 30 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 2020 are as follows:
- In each round, the top 100 participants get points according to [this table](https://pastebin.com/QT5sXEaT).
- The final result for each participant is equal to the sum of the points they got in the four rounds where they placed the highest.
- The top 30 participants over all series get sweatshirts and place certificates.
Thanks to XTX for sup...
[contest_time:1392] we will host [contest:1392]. This is the fourth round of a
2020 series of [Codeforces, - [user:antontrygubO_o,2020-08-12] for rejecting most of our problems
coordinating our round, 1. [user:boboniu,2020-08-16] 2. [user:maroonrk,2020-08-16] 3. [user:ecnerwala,
2020-08-16] 4, Thanks to XTX for supporting the global rounds initiative in 2020!, The prizes for the 6-round series in 2020 are as follows:, The problems in this round were prepared by [user:KLPP,2020-08-12],
[user:zscoder,2020-08-12, This is the fourth round of a 2020 series of [Codeforces Global
Rounds](https://codeforces.me/blog
Announcement of Codeforces Global Round 10
41.
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
Announcement of Codeforces Round 580 (Div. 1)
Announcement of Codeforces Round 580 (Div. 2)
42.
Codeforces Round #685 (Div. 2) Hi everyone!
I would like to invite you to another one of our rounds, that I set with my friends [user:Jeel_Vaishnav,2020-11-19], [user:FastestFinger,2020-11-19], [user:Utkarsh.25Dec,2020-11-19], [user:the_hyp0cr1t3,2020-11-19] and [user:ridbit10,2020-11-19]
We had two approved contests, but decided to merge it into one with more logical thinking ^_^
The round [contest:1451] that will take place on [contest_time:1451]. If your rating is less than **2100**, this round will be rated for you; otherwise, you can participate out of competition.
I would really like to thank my co-setters and:
- [user:300iq,2020-06-05] for coordinating our round and always replying quickly.
- [user:jtnydv25,2020-11-19], [user:antontrygubO_o,2020-11-20], [user:Monogon,2020-11-19], [user:Vivek1998299,2020-11-19], [user:tejas10p,2020-11-19], [user:smit_mandavia,2020-11-19], [user:T1duS,2020-11-20], [user:kshitij_sodani,2020-11-20], [user:ayushsinghiitr,2020-11-19], [user:Ajax,2020-11-19], [user:...
[user:Jeel_Vaishnav,2020-11-19], [user:FastestFinger,2020-11-19],
[user:Utkarsh.25Dec,2020-11-19, - [user:300iq,2020-06-05] for coordinating our round and always replying quickly, 1. [user:I_Love_Convex_Hull,2020-11-25] 2. [user:221,2020-11-25] 3.
[user:afterall,2020-11-25] 4, 1. [user:noimi,2020-11-25] 2. [user:I_Love_Convex_Hull,2020-11-25] 3.
[user:zhouzhendong,2020-11
Announcement of Codeforces Round 685 (Div. 2)
43.
I challenge you to a duel, Errichto (UPD: Saturday 11am PT) 
Dear [user:Errichto,2020-09-17],
In case you are unaware, you beat me by 3 seconds of penalty on [Facebook Hacker Cup Round 3](https://www.facebook.com/codingcompetitions/hacker-cup/2020/round-3/scoreboard). Upon deep reflection, I decided that I will not accept this lying down. In order to avenge this notorious defeat, I am challenging you to a 1v1 duel.
**Rules:**
1. Duel will be held as a lockout competition and will be televised live
2. Lockout problems will be chosen by a neutral problem setter
3. Loser must change their main to honor the winner. See below for details
~~~~~
// your template if you lose
#define stevenkplus main
int stevenkplus() {
// your code here
}
~~~~~
---
**Update:**
We're doing it this Saturday! https://www.timeanddate.com/worldclock/fixedtime.html?msg=Errichto+vs+Stevenkplus&iso=20200926T11&p1=224&ah=1
Will be broadcast live at https://www.twitch...
[user:Errichto,2020-09-17], In case you are unaware, you beat me by 3 seconds
of penalty on [Facebook, ://www.facebook.com/codingcompetitions/hacker-cup/2020/round-3/scoreboard).
Upon deep reflection, I, Dear [user:Errichto,2020-09-17],
44.
Codeforces Round #668 Hello Codeforces!
We are glad to invite you to [contest:1404] and [contest:1405], which will take place on [contest_time:1404].
The problems were created by [user:Ari,2020-09-04], [user:Kuroni,2020-09-04], [user:Maripium,2020-09-04], [user:Monogon,2020-09-04], [user:antontrygubO_o,2020-09-04] and [user:hugopm,2020-09-04].
We would like to thank:
- [user:dorijanlendvaj,2020-09-04], [user:Jatana,2020-09-04] and [user:MrDecomposition,2020-09-04] for helping with the preparation of the tasks.
- [user:gamegame,2020-09-04] for always being nice and supportive.
- [user:DatVu,2020-09-04], [user:Maripium,2020-09-04], [user:MofK,2020-09-04] and [user:atoiz,2020-09-04] for stealing the round #666, forcing us to retheme around ponies.
- [user:Monogon,2020-09-04] for making the author list more colorful.
- [user:TwentyFour,2020-09-04], [user:thenymphsofdelphi,2020-09-04], [user:qlf9,2020-09-04], [user:mcfr,2020-09-04], [user:Tlatoani,2020-09-04], [user:i_love_Lisa,2020-09-04...
take place on [contest_time:1404]. The problems were created by [user:Ari,2020
-09-04], [user:Kuroni, ,2020-09-09] 4. [user:w_o_kje,2020-09-09] 5. [user:veckoper,2020-09-09], - [user:DatVu,2020-09-04], [user:Maripium,2020-09-04], [user:MofK,2020-09-04]
and [user:atoiz,2020, - [user:MikeMirzayanov,2020-09-04] for the Codeforces and Polygon platforms., - [user:Monogon,2020-09-04] for making the author list more colorful., - [user:TwentyFour,2020-09-04], [user:thenymphsofdelphi,2020-09-04],
[user:qlf9,2020-09-04, - [user:dorijanlendvaj,2020-09-04], [user:Jatana,2020-09-04] and
[user:MrDecomposition,2020-09-04, - [user:gamegame,2020-09-04] for always being nice and supportive., 1. [user:maroonrk,2020-09-09] 2. [user:ainta,2020-09-09] 3. [user:ko_osaga,2020
-09-09] 4, The problems were created by [user:Ari,2020-09-04], [user:Kuroni,2020-09-04],
[user:Maripium,2020
Announcement of Codeforces Round 668 (Div. 1)
Announcement of Codeforces Round 668 (Div. 2)
45.
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...
Check out the similar blog for IOI 2019
[here](https://codeforces.me/blog/entry/68981).
46.
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
Announcement of Codeforces Round 556 (Div. 1)
Announcement of Codeforces Round 556 (Div. 2)
47.
Some thoughts on recent discussions Hello everyone!
I finally decided to write some response/explain my view after all recent discussions of my problems and rounds I coordinate, and I would like to make a few points.
**1.** After some recent contests there were a lot of comments saying that Data structure problems should appear as easy problems (say, D2A-D2D in a Div2 of $6$ problems)
I don't think I agree with this. To begin with, I don't think that having Data Structure problem is a requirement for a good contest at all, not just in first few positions.
However, for positions D2A-D2D, I just don't see a way to properly include data structure problems. Take some Data Structure problem, it consists from two parts:
<ul>
<li> Knowing/implementing the Data Structure </li>
<li> Actually thinking about the problem, and how this Data Structure...
* [user:MikeMirzayanov,2020-07-12] for great systems Codeforces and Polygon
48.
Codeforces Round #666 
(Translation: Hello)
We are very happy to invite you to take part in our contest, [contest:1396] and [contest:1397]. The contest starts on [contest_time:1396] and lasts **2 hours**. In both divisions, there will be **5 problems** for you to solve.
The problems were authored and prepared by [user:Maripium,2020-08-28], [user:DatVu,2020-08-28], [user:MofK,2020-08-28], and me.
We are very grateful and would like to sincerely thank the following people for their assistance in preparing the round:
- [user:300iq,2020-08-28] for coordinating our round and for reviewing and helping us with the problems.
- [user:minhtung04042001,2020-08-28], [user:TomOwO,2020-08-28], [user:EntityIT,2020-08-28] for their problem ideas and for helping us prepare the problemset.
- [user:codeveloppy,2020-08-28], [user:lolicon234,2020-08-28], [user:DeadlyCritic,2020-08-28], [user:growup974,2020-08-28], [user:VietCT,2020-08-28...
problems** for you to solve. The problems were authored and prepared by
[user:Maripium,2020-08-28, - [user:300iq,2020-08-28] for coordinating our round and for reviewing and
helping us with the, - [user:MikeMirzayanov,2020-08-28] for the _amazing_ platforms Codeforces and
Polygon., - [user:codeveloppy,2020-08-28], [user:lolicon234,2020-08-28],
[user:DeadlyCritic,2020-08-28, - [user:minhtung04042001,2020-08-28], [user:TomOwO,2020-08-28], [user:EntityIT,
2020-08-28] for, 1. [user:chokottodake,2020-09-01] 2. [user:1092515504,2020-09-01] 3.
[user:mickey639,2020-09-01, 1. [user:tourist,2020-09-01] 2. [user:Radewoosh,2020-09-01] 3. [user:aid,2020
-09-01] 4, The problems were authored and prepared by [user:Maripium,2020-08-28],
[user:DatVu,2020-08-28
Announcement of Codeforces Round 666 (Div. 1)
Announcement of Codeforces Round 666 (Div. 2)
49.
Goodbye, 2024. Hello, 2025! <img src="/predownloaded/85/58/8558df7ac8a1c33d501ea8fd9b18dd3d95886b90.png" style="width:290px; float:right; margin: 0 1.5em 1.5em 1.5em"/>
Goodbye, 2024. Hello, 2025!
Dear Santa Claus,
Please make 2025 a happy year—not just for me, but for everyone. We all need this.
Hello, 2025!
And of course, we have our traditional gifts!
#### <img src="https://assets.codeforces.com/images/wand.png"/> Change Handle Feature
Hurry! Until the 10th of January, you can change your handle (<b>but only once</b>)! Note that you can roll back the changes or request another handle change only _after a year_. Choose wisely!
You can change your handle to a new one that hasn’t been used by anyone else, or to one that you’ve previously used. Links to your old profile will automatically redirect to your updated profile.
Again this year, if you’ve participated in at least 10 rounds, you can request the handle of an _inactive_ participant. This means the participant must have had a perio...
lasting at most 180 days, and this activity must have occurred in 2020 or
earlier. The inactive
50.
Codeforces Global Round 11 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Hi!
On [contest_time:1427] we will host [contest:1427].
This is the fifth round of the 2020 series of [Codeforces Global Rounds](https://codeforces.me/blog/entry/65002). The rounds are open and rated for everybody.
The prizes for this round are as follows:
- 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 2020:
- 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.
- The best 20 participants over all series get sweatshirts and place certificates.
Thanks to XTX, which in 2020 supported the global rounds initiative!
Problems for this round ar...
**UPD5**: And congratulation to [user:Petr,2020-10-10] who upsolved H before
the editorial was, 1. [user:Benq,2020-10-10] 2. [user:yosupo,2020-10-10] 3.
[user:ksun48,2020-10-10] 4, Problems for this round are set by me. Thanks a lot to the coordinator
[user:antontrygubO_o,2020, Thanks to XTX, which in 2020 supported the global rounds initiative!, The prizes for the 6-round series in 2020:, This is the fifth round of the 2020 series of [Codeforces Global
Rounds](https://codeforces.com
Announcement of Codeforces Global Round 11
51.
touristreams are back! 006: SNSS 2020 R1, and more It's this time of the year again!
Tune in at [twitch.tv/the__tourist](https://twitch.tv/the__tourist) at around [21:45 MSK, 21 Aug 2020](https://www.timeanddate.com/worldclock/fixedtime.html?msg=touristream+006&iso=20200821T2145&p1=3396) to watch me solving [SnarkNews Summer Series 2020 Round 1](https://contest.yandex.com/snss2020/contest/19320/enter) live! First I will do the round competitively without much interaction, and I'll be up for discussing the problems on stream afterwards.
SnarkNews Winter/Summer Series (SNWS/SNSS) is organized by [user:snarknews,2020-08-19] yearly and consists of 5 rounds. Each round is a virtual 6-problem 80-minute contest open for 10 days. The series is open to all, but problem statements are in Russian only. Unlike last series, I'll be reading problem statements automatically translated to English on stream.
To make the stream more fun and for easier understanding of what will be going on, you're welcome to do the round yourself beforehand! If...
touristreams are back! 006: SNSS 2020 R1, and more, Aug 2020
](https://www.timeanddate.com/worldclock/fixedtime.html?msg=touristream+007&iso, /the__tourist) at around [21:45 MSK, 21 Aug 2020
](https://www.timeanddate.com/worldclock/fixedtime.html?msg, 2020
](https://www.timeanddate.com/worldclock/fixedtime.html?msg=touristream+006&iso=20200821T2145&p1, SnarkNews Winter/Summer Series (SNWS/SNSS) is organized by [user:snarknews,2020
-08-19] yearly and
52.
Ozon Tech Challenge 2020 Hello Codeforces!
<center>
<img alt="ozon" src="https://codeforces.me/predownloaded/6a/99/6a99904b94e5c20a149198e2dde4068dadd9278a.png" style="float:right; height: 200px; margin: 10px; max-width:50%;"/>
</center>
We are glad to invite you to the upcoming “[Ozon Tech Challenge 2020](https://codeforces.me/contests/1305)”, which will start at [contest_time:1305]. The round will be open and rated for everybody!
This round is initiated and supported by Ozon.
Ozon — one of the leading players in e-commerce (provides its customers with over 2.5 million product names in 24 categories), a tech company that actively developing its IT department. They already have the largest Golang team in Russia, a proprietary WMS fulfillment management system completely written by the Ozon team, 250 million lines of logs per day, collected on the site and in the Ozon mobile application. Ozon experts perform at the leading profile conferences GoperCon, Heisenbug, GoWayFest, GolangConf, and also ...
Ozon Tech Challenge 2020,
* [user:Benq,2020-03-03] ,
* [user:Endagorion,2020-03-03] ,
* [user:Maripium,2020-03-01], [user:gamegame,2020-03-01], [user:hugopm,2020
-03-01,
* [user:Um_nik,2020-03-03] ,
* [user:gisp_zjz,2020-03-03] ,
* [user:maroonrk,2020-03-03] ,
* [user:neal,2020-03-03] ,
* [user:peehs_moorhsum,2020-03-03] ,
* [user:tourist,2020-03-03] ,
* [user:yasugongshang,2020-03-03] , %;"/> Мы рады пригласить вас на общий рейтинговый раунд “[Ozon Tech Challenge
2020, The problems were created by [user:Akikaze,2020-03-01], [user:Ari,2020-03-01],
[user:Kuroni,2020-03, Задачи раунда были придуманы [user:Akikaze,2020-03-01], [user:Ari,2020-03-01],
[user:Kuroni,2020-03
53.
Testing Round #16 (Unrated) Hello, Codeforces!
Paul [user:stingray,2020-05-07] Komkoff is my hero! He found some issues in the network configuration. The most important of them was about flow control auto-negotiation: in case of our network routers the number of dropped packets reduced in times. Thanks!
To be sure that it really helped to fix the issue I ask you to take part in [contest:1351]. It will start on [contest_time:1351]. Probably, it will contain 3 easy problems which are not prepared for now (I'll use some old problems, I think). The only reason to host the round is to check the system under a load. It will be an unrated round.
I am upset about what happened with the last round. Once again, I apologize to both the participants and the writer, coordinator and testers. I wrote [user:Monogon,2020-05-07] about the incident and apologized.
I am sure that the only way to **absolutely** prevent unrated rounds is just don't host them. And this is not my way. The most popular rounds were hosted with...
participants and the writer, coordinator and testers. I wrote [user:Monogon,
2020-05-07] about the incident and, Paul [user:stingray,2020-05-07] Komkoff is my hero! He found some issues in the
network
Announcement of Testing Round 16 (Unrated)
54.
[Tutorial] Generating Functions in Competitive Programming (Part 1) Hi everyone! Inspired by the recent [Codeforces Round 641](https://codeforces.me/contest/1349), I decided to write an introductory tutorial on generating functions here. I am by no means an expert in generating functions so I will write about what I currently know about them. [user:MiFaFaOvO,2020-05-15] has written a really interesting [blog](https://codeforces.me/blog/entry/76447) here on Codeforces about more advanced applications of generating functions, but I think there is no English tutorial on the basics of this topic yet (or at least on CP sites). Thus, I would like to share about this topic here.
I plan to split this tutorial into two parts. The first part (this post) will be an introduction to generating functions for those who have never learned about them at all, and some standard examples and showcases of generating functions. The second part will be a collection of several applications of generating functions in CP-style problems. If you are already familiar with ge...
in generating functions so I will write about what I currently know about
them. [user:MiFaFaOvO,2020
55.
Codeforces Round #655 (Div. 2) Hey everybody!
We ([user:MagentaCobra,2020-07-05], [user:Tlatoani,2020-07-05], [user:golions,2020-07-05], [user:qlf9,2020-07-05]) are super excited to invite you to take part in [contest:1372], which will happen on [contest_time:1372]. _Please note the unusual start time_. The round is rated for users with rating strictly less than **2100**, although higher rated users are more than welcome to take part out of competition.
Huge thanks to those who helped make this round possible:
- [user:Tlatoani,2020-07-06], [user:golions,2020-07-06], [user:qlf9,2020-07-06] for creating problems and preparation
- [user:antontrygubO_o,2020-07-05] for r̶e̶j̶e̶c̶t̶i̶n̶g̶ ̶m̶o̶s̶t̶ ̶o̶f̶ ̶o̶u̶r̶ ̶p̶r̶o̶b̶l̶e̶m̶s̶ coordinating our round
- [user:gamegame,2020-07-05], [user:dorijanlendvaj,2020-07-05], [user:thenymphsofdelphi,2020-07-05], [user:aryanc403,2020-07-05], [user:Ari,2020-07-05], [user:alireza_kaviani,2020-07-05], [user:KonaeAkira,2020-07-05], [user:Mn619,2020-07-05], [user:AmShZ,2020-07...
- [user:Tlatoani,2020-07-06], [user:golions,2020-07-06], [user:qlf9,2020-07-06]
for creating, Hey everybody! We ([user:MagentaCobra,2020-07-05], [user:Tlatoani,2020-07-05],
[user:golions, We ([user:MagentaCobra,2020-07-05], [user:Tlatoani,2020-07-05], [user:golions,
2020-07-05
56.
Codeforces Round #652 (Div. 2) $$~-\text{In the name of God}~-$$
Hi community,
I'm glad to invite you to my first contest, [contest:1369] which will be held at [contest_time:1369] ($\text{notice the unusual time}$). The problems are mainly prepared and invented by me. The round is rated for participants with rating strictly less than $2100$, others are able to take part in the round out of competition. You will be given $2$ $\text{hours}$ to solve $6$ $\text{problems}$.
Firstly I'd like to thank [user:adedalic,2020-06-15] for coordinating and reviewing the round, as well as helping with many different things.
I'd like to thank [user:antontrygubO_o,2020-06-21], [user:physics0523,2020-06-21], [user:McDic,2020-06-21], [user:Ashishgup,2020-06-21], [user:dannyboy20031204,2020-06-21], [user:Kuzey,2020-06-21], [user:Return_0,2020-06-21], [user:FieryPhoenix,2020-06-21], [user:ma_da_fa_ka,2020-06-21], [user:ITDOI,2020-06-21], [user:AM_I_Learning,2020-06-21], [user:pikmike,2020-06-21], [user:lynmisakura,2020-06-...
,2020-06-15] for coordinating and reviewing the round, as well as helping with
many different things, Also I'd like to thank coauthors, [user:amiralisalimi,2020-06-21],
[user:AS.82,2020-06-21] and, Finally, thanks to [user:MikeMirzayanov,2020-06-15] for very nice and
convenient Codeforces and, I'd like to thank [user:antontrygubO_o,2020-06-21],
[user:physics0523,2020-06-21], [user:McDic,2020
Announcement of Codeforces Round 652 (Div. 2)
57.
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
Announcement of Good Bye 2018
58.
Remove Virtual Contestants from Contest Leaderboards As most of you are likely aware, cheating in virtual contests (typically by submitting prewritten or copied solutions in order to appear at the top of the leaderboard) is very common. Most recently, [user:wannabecandidatemaster,2020-05-28] submitted solutions to all problems in [this round](https://codeforces.me/contest/1358/standings) in order to take first place in the standings, and [user:bemandrei,2020-05-28] competed virtually in [this round](https://codeforces.me/contest/1360/standings) after competing in the round officially, and ended up in second place on the leaderboard.
In response to the rise of VC cheating (as well as some other issues with the VC system I'll describe below), I'd like to make a simple proposal: **Remove all virtual participants from the contest leaderboards.** The one exception is that you should see your own name on leaderboards for contests you VCed (that is, virtual contestants should be visible only to themselves). Similarly, virtual participan...
, [user:wannabecandidatemaster,2020-05-28] submitted solutions to all problems
in [this round](https
59.
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
60.
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.
...
between 31 and 500, inclusive. The prizes for the 6-round series in 2019: - In
each round top-100, 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
Announcement of Codeforces Global Round 4
61.
Codeforces Round #647 — Thanks, Algo Muse! Hello Codeforces!
We have a pleasure to invite you to [Codeforces Round #647 (Div. 1)](https://codeforces.me/contests/1361) and [Codeforces Round #647 (Div. 2)](https://codeforces.me/contests/1362). This round will take place on [contest_time:1361]. In both divisions, you will have **2.5 hours** to solve **6 problems**. Three of them will be shared.
The problems for this round were prepared by [user:MicGor,2020-06-02], [user:Grzmot,2020-06-02], [user:Okrut,2020-06-02] and me.
We would like to thank everyone who made this round possible:
- [user:Nebuchadnezzar,2020-06-02] for the excellent coordination;
- [user:Lewin,2020-06-02], [user:ALILILILILI-KHAN,2020-06-02] for invaluable advice and extensive testing;
- [user:KrK,2020-06-02], [user:yarek,2020-06-02], [user:-is-this-fft-,2020-06-02], [user:w0nsh,2020-06-02], [user:Marckess,2020-06-02], [user:Ari,2020-06-02], [user:Fortin,2020-06-02], [user:Dup4,2020-06-02], [user:kraborak,2020-06-02], [user:300iq,2020-06-02], ...
prepared by [user:MicGor,2020-06-02], [user:Grzmot,2020-06-02], [user:Okrut,
2020-06-02] and me. We, - [user:KrK,2020-06-02], [user:yarek,2020-06-02], [user:-is-this-fft-,2020
-06-02], [user:w0nsh,2020, - [user:Lewin,2020-06-02], [user:ALILILILILI-KHAN,2020-06-02] for invaluable
advice and extensive, - [user:rainboy,2020-06-05] - [user:Charbel11,2020-06-05] - [user:firecookie,
2020-06-05] - [user, - [user:tourist,2020-06-05] - [user:Um_nik,2020-06-05] - [user:boboniu,2020
-06-05, The problems for this round were prepared by [user:MicGor,2020-06-02],
[user:Grzmot,2020-06-02
Announcement of Codeforces Round 647 (Div. 1) - Thanks, Algo Muse!
Announcement of Codeforces Round 647 (Div. 2) - Thanks, Algo Muse!
62.
[Repost] "Justice may be delayed, but it cannot be absent": New Evidence on
NXIST's Cheating Scandal
[Repost] "Justice may be delayed, but it cannot be absent": New Evidence on NXIST's Cheating Scandal _Original post: [「正义可以迟来但不能缺席」：关于 NXIST 的一些新证据](https://zhuanlan.zhihu.com/p/620297880)_
_Translated by GPT-4 with some adjustment. Please inform me if there are any mistakes._
_All links to the invalid repository have been redirected to the backup repository._
**This article provides a logically complete set of evidence, which does not involve any non-public internet resources, regarding the "suspected cheating" incident involving the ICPC Yinchuan Station and ICPC Shenyang Station in 2021. By discovering the suspected GitHub account ([NaokiLH](https://github.com/NaokiLH), renamed to https://github.com/brokenTarget) of a team member from Ningxia Institute of Science and Technology (NXIST) TS 1 team, Lan Hao, two years ago, and by mining and analyzing the commit records of his algorithm competition repo, we have obtained direct evidence that at least 4 questions from the 2021 Yinchuan regional contest set and at least 6 questions (including scrapped questions) from the 2021 Sh...
](https://pic4,  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...
automatically checking a lot of stuff). We both checked the statements (and
[user:antontrygubO_o,2020, received a message from [user:MikeMirzayanov,2020-12-09] asking to propose
rounds (it was sent to a number
64.
Codeforces Round #672 (Div. 2) Hello, Codeforces!
I am very glad to invite you to the [Codeforces Round #672 (Div. 2)](https://codeforces.me/contest/1420), which will take place in [contest_time:1420]. <b>This round will be rated for the participants with rating lower than 2100</b>.
All tasks were made by me, but [user:gepardo,2020-09-22] helped me a lot with the last two tasks, probably these tasks wouldn't have appeared if he didn't help me.
My thanks to:
- [user:antontrygubO_o,2020-09-22] for coordinating this round. With this great coordination only good tasks remained in the contest.
- [user:gepardo,2020-09-22] made a lot, there wouldn't have been this contest if he didn't help me. He not only helped me with making last two tasks, but also helped me to understand how to make tasks for Codeforces rounds. Thanks!
- [user:EIK,2020-09-22] this is the person who teached me competitive programming — my Informatics teacher. Thanks!
- [user:programmer228,2020-09-22], [user:Hacktafly,2020-09-22], [...
- [user:Osama_Alkhodairy,2020-09-22], [user:vamaddur,2020-09-22],
[user:thenymphsofdelphi,2020-09, - Тестировали задачи и предоставляли свой бесценный фидбек
[user:Osama_Alkhodairy,2020-09-22
Announcement of Codeforces Round 672 (Div. 2)
65.
Goodbye 2022. Hello 2023! <img src="/predownloaded/f4/1f/f41ff0beb745fb2f84a55d9f2cc451273efc6267.jpg" style="width:300px; float:right; margin: 0 1em 1em 1em"/>
Dear Santa Claus. Please make 2023 a happy year, not just that. Please, we all need this.
Hello, 2023!
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 handle to the new one which wasn't used before by anybody or which was used by you before. The links to a profile page with an old handle would automatically redirect to the actual profile.
Again, this year if you took part in at least 10 rounds you can request a handle of an _inactive_ participant. It means that the participant should have a period of activity on Codeforces
of...
180 days, this period should be in 2020 or earlier. The inactive participant
can't have posted
66.
Петиция по поводу флага Беларуси Привет всем беларусам, которые активно, или не очень, участвуют в жизни замечательного сообщества Codeforces.
Хотелось бы заручиться вашей поддержкой в том, чтобы инициировать смену флага Беларуси на данном ресурсе на исторический [бело-красно-белый флаг](https://ru.wikipedia.org/wiki/%D0%91%D0%B5%D0%BB%D0%BE-%D0%BA%D1%80%D0%B0%D1%81%D0%BD%D0%BE-%D0%B1%D0%B5%D0%BB%D1%8B%D0%B9_%D1%84%D0%BB%D0%B0%D0%B3), потому что государственный флаг Республики Беларусь стал стойко ассоциироваться с преступлениями против человечности, с той жестокостью, пытками, зверствами, нарушениями прав человека, которые, к сожалению, стали обыденностью в последние месяцы в нашей прекрасной стране.
<html>
<body>
<img src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Flag_of_Belarus_%281918%2C_1991%E2%80%931995%29.svg/500px-Flag_of_Belarus_%281918%2C_1991%E2%80%931995%29.svg.png" style="display: block; width:30%; margin: 0 auto; border: 1px solid black">
</body>
</html>
Вне публичной ...
(Idea author: [user:vladik,2020-09-30], author of the text: [user:sdryapko,2020
-09-30]), (Автор идеи: [user:vladik,2020-09-30], автор текста: [user:sdryapko,2020-09-30])
67.
Codeforces Round #649 (Div.2) Hi everyone!
Codeforces round #649 will take place on [contest_time:1364]. It's rated for the second division, but, as usual, first division participants can take part out of competition.
The problems were created by me. I'd like to thank my forever orzable coordinator [user:antontrygubO_o,2020-06-11]; my incredible army of testers [user:dorijanlendvaj,2020-06-11], [user:300iq,2020-06-11], [user:Osama_Alkhodairy,2020-06-11], [user:AmShZ,2020-06-11], [user:Taran_1407,2020-06-11], [user:TigranMec,2020-06-11], [user:_Aaryan_,2020-06-11], [user:Mohammad_Yasser,2020-06-11], [user:zoooma13,2020-06-11], [user:lavish315,2020-06-11], [user:Utkarsh.25dec,2020-06-11], [user:NOOBxCODER,2020-06-11], and [user:Laggy,2020-06-11]; and, of course, you-know-who for the amazing codeforces and polygon platforms.
This time, in an effort to kill type-races and because I'm lazy, you'll be given 5 problems and 2 hours to solve them.
**UPD:** the scoring distribution will be 750-1000-1500-2000-2500...
[user:antontrygubO_o,2020-06-11]; my incredible army of testers
[user:dorijanlendvaj,2020-06-11], [user:300iq,2020-06, ,2020-06-11]; my incredible army of testers [user:dorijanlendvaj,2020-06-11],
[user:300iq,2020-06-11, 1. [user:SanyaSaske,2020-06-13] 2. [user:Chloristendika,2020-06-13] 3.
[user:el_risitas,2020-06
Announcement of Codeforces Round 649 (Div. 2)
68.
C++ tips and tricks Hello, codeforces.
I would like to tell you about some tricks and constructions I use in C++. They are not hidden or anything, moreover, most of them are from stl or maybe well known among software engineers, but I often see codes where something is done by hand in, say, 5 lines, while in stl there is a function which does the same.
The things below are filtered by my personal sense of non-popularity (so no `__builtin` functions) and usage frequency (so there almost surely are similar things I don't know about) and are not really sorted in any reasonable order. Let's begin. [cut]
<hr>
- ### `all(x)`
This may be an exception to the rule of non-popularity -- this is quite widely used, but some next items will depend on `all(x)`, so I define it here. So, I talk about
```[c++]
#define all(x) (x).begin(), (x).end()
```
Now sorting a vector looks like `sort(all(vec))` instead of `sort(vec.begin(), vec.end())`.
However, it's not all about this define. Imagine you nee...
Big thanks to my friends and colleagues [user:Wild_Hamster,2020-03-14],
[user:ArtDitel,2020-03-14
69.
My thoughts on clarifications and on the round #677. Alright, I'm done. I wanted to write a blog like that for a long time, but now I really don't have enough patience to ignore this issue anymore.
I want to say that I get 100-200 clarifications each Div.3 round. It doesn't even matter how well the statements are, it doesn't matter if there are any issues with solutions or checkers, people always find what to ask.
Before I start whining here, I really want to recommend anyone to read these two [user:Um_nik,2020-10-20] blogs: [this one](https://codeforces.me/blog/entry/62730) and [this one](https://codeforces.me/blog/entry/62744). Sorry, [user:Um_nik,2020-10-20], I unnecessarily tagged you, I will not do that anymore.
Now some breaking news for most participants: _your local IDE compiler_ and _Codeforces compiler_ are **actually** different things! If your code works fine locally but gets WA/TL/RE/ML/etc on Codeforces, it (most probably) means you have a bug somewhere in your code. There are rare cases when the issue is with comp...
Before I start whining here, I really want to recommend anyone to read these
two [user:Um_nik,2020
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