Hi,

From now on, we are going to provide video editorials for Codeforces rounds. So, Codeforces rounds are not going to be limited to text editorials, but also video editorials!

We want to seek feedback and try to improve these video editorials as much as possible. We will try different ideas like recorded videos and livestreams to see which one helps you the best. So, please help us make a better content for you!

The blog will be shortly accessible in contest materials.

1986A — X Axis

1986B — Matrix Stabilization

1986C — Update Queries

1986D — Mathematical Problem

1986E — Beautiful Array

1986F — Non-academic Problem

1986G — Permutation Problem

I hope it helps!

Hey Guys, The interview with Adamant will be released on Saturday Jun 22, 17:00 GMT. We will talk from his work at Google to his new project OCPC and what are his hobbies. (Turns out that he is a gamer and watches animes) You may want to watch that!

And again, I will try to continue inviting interesting guests. I have a list already, if you wanted to suggest someone, feel free to let me know!

You can find the link of the video in the streams section of Codeforces! You can watch the video from Codeforces or from Youtube.

First day

We have North America Championship from today (May 23rd) to May 28th in Orlando, Florida. This competition is for choosing the teams qualifying to ICPC WF 2024 in Kazakhstan.

I will make a vlog for each day. I'm trying to make each one of these vlogs 15 mins. My first try wasn't very successful and the first video is about half an hour. (It was good and I couldn't trim more than this)

By the way, we did the real duel with galen_colin and we tried to headshot each other using frisbees. We are both alive but injured.

Everyday, This post will be updated by the vlog of that day. Hope you'll enjoy, feel free to give me suggestions about the next ones. And definitely wish UMD White luck :)

Second Day

I heard a sad news from Mohamed Bakry today. As he said, Iran and Israel cannot attend IOI 2024 onsite and this is told to them about a year ago. I personally don't know what can we do in this situation to prevent such things to happen again.

I also had a short talk with ecnerwala today. Then, we participated in the practice round today. We got the second rank, after MIT. They solved 7, we solved 6, the next teams (Waterloo and Stanford) solved 5.

There was a lot of fun back in the hotel too. Many hilarious things happened.

Third day

Everything was very similar to the second day. We had another practice round. We did not perform well in this one. I also met and had a short talk with SecondThread. Again, we had most of the fun back in the hotel.

Fourth Day

we had dress rehearsal round. It was basically training all the rules of the main contest with a practice round. We won it. Problems were super easy and some of them were from the previous rounds, so this does not mean anything. However, even winning meaningless competitions doesn't feel bad.

There was another round, NSA challenge. We performed poorly in it. The contest was not very good either (was not very competitive programming-ish). We got the 7th place.

Have you heard about link-cut tree? Today, I met its inventor, Professor Daniel Dominic Sleator. I recorded a short talk with him.

I also had a very short talk with our rival, MIT team. (djq_cpp, TLE, and duality) The scary fact about them is that the max rating of all of them is around 3300 ~ 3400. So, we can simply give up the first rank and fight for the second one.

The big day is tomorrow. You can watch the livestream on ICPC official YT channel. It seems like it has some cool features. Each team has a dedicated camera, and you can comment the name of a team to see them, and they will show that team to you. (You can see what they are doing at that moment) It seems cool.

We don't have any Chinese team member. So, wish us luck, we need that!

Fifth Day

We had our contest on the fifth day. We were not at our best, however, we won some very valuable awards. We got:

Qualified to World Final 2024, Astana, Kazakhstan, NAC Bronze Medal, South division, J first accept, $7500 ($3000 for bronze, $3000 for winning South, $1500 for J first accept)

As expected, MIT won the gold medal.

Yeah, now we need to train to get in shape better. Because we need to be at our best in the WF.

Final Day

The contest is over, and in the final day, we decided to go to Disney World. Actually, it was more fun than expected. You can watch this final vlog in the link provided below.

It's over, and now we have to get ready for the next challenge. This is the last update of this blog. Thank you for following!

Videos

Day #1 (Coming to Florida and settling in)

Day #2 (Iran cannot attend IOI 2024, Short Talk with ecnerwala, Practice Round, Missing Frisbees)

Day #3 (Career Fairs, Second Practice Round, Short Talk with SecondThread)

Day #4 (Winning Dress Rehearsal Round, Talk with Link-Cut Tree Inventor)

Day #5 (Won Bronze and South)

Day #6 (I Rode an Ikran! | Many Disneylands, but One Disney World!)

Photos

Well, since you like it even more than educational content, I'm starting to upload more of them.

Yesterday, we had Codesprint LA, an online ICPC style contest. Our team (UMD White, galen_colin, sam571128, and I) participated in it. We ended up ranked 6th in total, and 1st amongst the universities who participated. (teams that are eligible for NAC)

Who won the first place? Well, as usual, tourist with his two teammates.

We recorded some parts of it. The cam was on by itself and we were trying to solve problems. I uploaded it to youtube and you can watch it here.

And, as announced, we are going to do the duel today!

EDIT: Because of clashing with the div 2 contest, I will postpone the interview for one day.

Hey,

First, I want to mention that my interview with orz is going to be out on Friday 17:00 GMT. I will soon schedule it!

orz is a unique competitive programming legend! He has a gold medal in IMO (Um_Nik has had qualified to IPhO and orz has a gold medal in IMO, I don't know what is the problem of CP legends with IOI) He was a participant in ICPC 2024 World final. And of course, he is an IGM in Codeforces. He is currently studying PhD in mathematics and works in a startup.

Maybe we (orz and I) will have live commentary on the interview and be active in the chatbox while it is streaming. (If it makes it more interesting ofc)

You can view the trailer here:

https://www.youtube.com/shorts/5rZNLpAq8Tc

Also, I have another (maybe?) interesting material. I decided to upload a vlog of IOI 2022! (after two years lol) Because it was too dope and I'm sure it gives people a lot of motivation! Therefore, I found it very useful even after two years. So, I hope you will enjoy it.

Here is the link of this video: https://youtu.be/Oqz6Lx6Edok

And, you can find some pictures of this vlog below.

Ok, I know it took so much time, but it worth it!

Um_nik, in one word, is a legend. After this interview I found a lot more about him.

Like what? He didn't do IOI and IMO in high school, instead he advanced to IPhO! (International Physiscs Olympiad) He is the champion of ICPC in 2020. Once, he was at the first place of CF for a few weeks (in 2018).

If you are surprised, don't be yet. The real surprise is when he says he doesn't believe in talent!

I will discuss many things with him. It took more than an hour (I wanted to keep it short, but I really couldn't, it was so good that I couldn't remove any part)

He talks about his advices to competitive programmers, his own journey, what happened after he posted the solutions of a div 3 round (during the contest lol), what he did on the 4th Dec 2016 (double lol), his opinion about many different things, and definitely I asked him your questions!

I invite you all to watch this interview on Friday April 5, 17:00 GMT. You can watch later as well, but let's watch it together and chat.

Here are the trailers:

Trailer 1: https://www.youtube.com/shorts/QwR-ihtHvUc

Trailer 2: https://www.youtube.com/shorts/Qi7wzF_BQuM

Trailer 3: https://www.youtube.com/shorts/9EbAZMsjgwo

PS1: I separated the educational channel and the interviews channel.

PS2: Let me know which trailer you liked the best. It helps for making the trailers of the next interviews.

PS3: Tell me who you want me to interview next!

Hey guys,

Yesterday, we won both the Mid-Atlantic region of North America ICPC and the whole South Division (including the Mid-Atlantic, South Central, and Southeast Regions). Our team consists of Colin Galen (galen_colin), Sam Lee (sam571128), and me (Shayan). We are UMD White from the University of Maryland.

I created a vlog for the whole day of the contest. I hope you enjoy it.

https://www.youtube.com/watch?v=OMozjSNLS14

The next round is NAC (the whole USA and Canada will participate). It will be in around 2 months. If we perform well, we will qualify to the World Final.

Hi, I want to share a very interesting proof for the existence of centroid.

Let's direct each edge to the side that has more vertices. (direct randomly if equal) Then you have n vertices and n-1 edges, therefore at least one vertex has an outgoing degree of 0. (If for every vertex the outgoing degree was at least one, we needed at least n edges) This vertex is your centroid. (Because all edges are directed towards it, so no child has more than n/2 vertices).

Using this approach, not only you prove centroid exists, but you can also find it.

I explained it in detail and with visuals in my video on centroid #2 here: https://www.youtube.com/watch?v=t74JJlMIQv8

Recently many people wanted me to talk more about more advanced topics. So I thought maybe I should share this here. (not many people had watched the video)

If you like such facts, let me know. I will make more videos about them.

Let me know about your opinions.

I want to say that if I'm doing anything wrong, I'm sorry. I planned to do something big and make a big positive change, but I received hate in response. I don't think it was fair. But, maybe I was doing something wrong, and I'm sorry about it.

You can read this blog to see what I'm talking about. https://codeforces.net/blog/entry/125745

I don't intend to defend myself. I just have one request. Help me figure out what I did I do wrong that I'm accused of being unethical here.

Do you want to stop doing it? What should I do?

I was thinking about many things that I might have done.

As kostka mentioned many times, duplicate accounts (Shayan and Algorithms_with_Shayan).

I'm sorry for it. As I mentioned once Algorithms_with_Shayan is not my personal account and I think it is not against the policy. But from now on, I won't do anything in that account anymore. I will have this account. That account can be banned. I'm sorry if I did anything against the policy. Does that resolve it?

My conversation with TheScrasse about the stream.

I never did anything against your consent, my friend. But you tried to show everyone like I used you or something? I don't understand why?

I never share my chats. Here, some part of the chat is exposed in the other blog and some parts are hidden. People are accusing me of using TheScrasse. So I have to show this.

This is how we decided to do the streams. I used anyone? I talked bad with anyone?

I'm sorry if I had done anything wrong.

Please tell me what is the reason you wrote against me so that maybe I can stop it.

Do you want me close my YT channel? Do you want me to stop getting help from others to stream for me? What I am doing wrong that you insult me like this and accuse me of being unethical?

Somebody tells me that I used people. Someone tells me my videos are bad. Someone tells me you are muslim!

The word 'exposed' is used for criminals or at least someone who has done something bad. Right? Can you tell me my crime? Making bad videos?

I can't understand any of these.

I'm not an enemy, tell me what disturbs you and I can stop that.

Hello Codeforces!

We are going to hold some online OI-style contests, the tasks are the selected tasks, chosen from the older Iran national team selection contests.

The level of these contests is around the IOI, maybe a bit simpler, and the main reason of them is to help Iranian students to prepare better for the summer camp contests, which will be held around 3 weeks from now and the national medalists will be chosen there.

And also we did translate tasks to English, so that if anyone from anywhere wanted to prepare for the IOI or other competitions could use it too.

We will have 1 contest per week, and you can freely choose 5 hours to participate in the contest, after each contest the top performers will be announced.

You can participate in contests on the inoi-judge website, the first contest time period starts from Aug 10. 08:00 GMT, There is no need of registration from now, whenever a contest starts you can go and participate in it.

Also, you can see tasks of this year’s contests in the problemset, just keep in mind that you should first login to see the tasks.

And also you can join our telegram channel if you want, further content and posts will be there.

The INOI Team Selection 2021 Online Mirror Competition has ended, now the second-day contest’s tasks are on the judge for upsolving, and statements, editorials, and testcases of tasks released here.

We want to apologize if there were any issues in the contests and thank all the people who gave us feedback.

We had an interesting talk with Zixiang Zhou (duality) who has won 2 gold medals and a silver medal in IOI at age 16 and also got 600 points in our competition. we asked some questions about himself, how he practices and his strategy in the contests. We believe it can be beneficial for everyone. You can see this talk in our telegram channel.

Also, soon we will have online mirrors of our summer camp contests and our Regional ICPC, and some other stuff.

Hope this will be helpful.

Hello everyone!

We are glad to invite you to participate in the Iran National OI Team Selection contests.

Every year in Iran, the Iranian National Olympiad in Informatics (INOI) committee conducts a summer camp to choose 8 top students to prepare them for next year's IOI and a spring camp to choose 4 out of those 8 to form the Iranian national team in IOI.

After the successful experience of holding the mirror of last year’s summer camp contest with few contestants, we are going to have the mirror of our national team selection on a larger scale. The level of these contests is around the IOI, and harder than the contests of the summer camp, and the point of holding the mirror of these contests is to help the IOI participants from other countries to prepare better for the IOI, and Persian younger students to have experience of these contests and prepare better for the future.

Now we want to invite the codeforces community to participate in the contests too.

Two contests will be held, each contest will have 3 problems with subtasks and duration of 5 hours, statements will be available in both English and Persian, you will have 7 days time, first 4 days are for participating and you can freely choose 5 hours to participate in the contest, after this 4 days tutorials will be released and you will have 3 days for upsolving problems, after that, the judge will be down.

The first contest time interval begins from May 29. 08:00 GMT, and the second contest time interval begins from June 5. 08:00 GMT. Contests will be held in inoi-judge, and you can see summer camp problems and other announcements there too, for more announcements and discussions you can join our telegram channel.

The whole ranking will be released after the contests, and the top 8 and the top 8 of Persian students under age 18 will be announced as honorary gold medalists, the dataset will be released for the public too, but if you wanted to use our problems in some contests or training camps, please contact us via [email protected] and inform us.

PS:

The chosen national team this year is:

1. Ali Safari (Amoo_Safar)
2. Alireza Kaviani (alireza_kaviani)
3. Ali Shahali (AliShahali1382)
4. Alireza Keshavarz (Keshi)

In most of these last years we had rank around 3 to 5 in IOI, hope this team will end up with rank 1 or 2 and break our record. :)