Hello everyone, I am very proud to announce that the second Iranian Combinatorics Olympiad is going to be held soon, also, I will publish the official poster and text for more information.

**Official text:** Have you ever thought about how scientists are improving artificial intelligence? How do banks predict whether a start-up will be successful or not? Or even how these new navigators can find the fastest way to your destination in a crowded city? Lots of you might think of mathematics. Well, that's right; but if look more closely, the basic idea for these achievements is Combinatorics.

Combinatorics is one of the main areas in mathematics which is widely used for solving problems in the real world. By solving combinatorics tasks, you can improve your logic and proving skills.

Interested in combinatorics? We have a very good news for you! Try yourself with some high-quality problems and have a lot of fun by participating in IranianCombinatorics Olympiad.

Iranian Combinatorics Olympiad is a competition in which you can test your skills in groups of three but what makes us unique is having an online scoreboard for a proof-based competition, maybe for the first time in the world. So don't miss this opportunity, gather a team, register for the ICO2021 exam, and compete for medals! Also, feel free to ask us any question that comes to your mind.

Our email address: ico_live@ico-official.com

Update1: Any team from around the world can participate in ICO2021

Update2: You can find the previous year problems in the website or our channel

You can also ask any question about the competition here as well

Is this similar to Iranian Geometry Olympiad?

Yes, it is. But this time for Combinatorics

Where can I find the problems of the first olympiad(last year's problems)

The problems of the previous round are available in the ICO official telegram channel. ICO

Can people from other countries also participate??

Yes for sure, that's why I post this here

I looked at the past problems, absolutely beautiful questions!

We are so pleased to hear that, Hope to see your team in the new season

Hi Aryan, great news! The community is very excited about the competition.

Regarding "Update1", will Israeli teams be eligible to participate?

Thanks in advance, FiveSixFiveFour.

Hi, Well, in this special case, I am not aware of the exact rules and you should ask the directors using the email addresses in the poster.

Thanks for your interest in our exam, Aryan

lmao why is it after IMO

One of my friend tell me about ICO as it written below:

"I have participated in the past ICO, I truly enjoyed the system of live standing and difficulty of the questions. My team and I are coming for the medal this year… I recommend everyone to participate in this competition."

I think it is hard to wait for the day of ICO2021...

Hope to see your's and your friend's team in the ICO2021.

aryanv Where can we find the solutions to the short answer exam for the previous edition of this competition?

kanishk779, you can find the solutions for the short answer exam and the main exam by checking our website using the link in Update2 and downloading the 2020 booklet. Complete answers are written their

Hopefully we can participate in ICO again. online scoreboard is great for Combinatorics. Thank you for informing us.

Wtf? How is combinatorics used in all of these?

Believe me, I was about to comment same thing until I saw your comment lol

For example combinatorial optimization has applications in artificial intelligence and navigations use graph theory. You can search in google for more information. Combinatorics has applications in a very wide range!

Combinatorial optimization != combinatorics

That's a very loose definition of combinatorics.

Agreed, that's all bad examples and each of them requires some other mathematical or CS areas. Basically, I can list the most relevant ones because worked with each "question" to some degree.

Have you ever thought about how scientists are improving artificial intelligence?Mathematical analysis, statistics, modelling etc.

How do banks predict whether a start-up will be successful or not?Data analysis.

Or even how these new navigators can find the fastest way to your destination in a crowded city?Graph theory, geometry.

No combinatorics! At least explicitly.

I'm very intrigued by this — what does this mean? Will there be live grading of the solutions? If so, how exactly will the grading process work (especially since math olympiads are kinda hard to grade at a glance)?

Hello, Thanks for your attention. Yes, there will be live grading for the solutions, we will ask the participants to write down their full solution and upload that to our website. We have asked a lot of IMO and other competitions graders to grade the solutions lively and that's how we can have live standing during the contest.

Is there an age limit for this? (i.e. are university students eligible?)

Hi, The exam will be in three levels:

Elements(Students in Grade 9 or below) Advance(Students in Grades 10 and 11) Free(There is no age limit at this level) And yes University students are eligible at the free level

Hello. Happy to hear that. I will participate for that. It's really good for whom studies IOI & INOI. And one thing forgotten. You can Register in ICO2021-Registraition and main Website is -->> ICO-Official

Hi, We are happy to hear that and also thanks for your additional information. Wish you the best results in ICO2021

Hi, I don’t believe that talking about the applications of combinatorics is the thing that we should discuss, in this blog but it becomes a factor that I can write about the application of the combinatorics in my past researches or studies: First of all, finding the shortest path in a weighted graph which is equivalent to the simple model of the real world, and finding the route between the beginning point to the destination is one of the usages of combinatorics. For sure we should use a bit prediction in real-world tasks according to changing the weights of edges during the time for example: https://ieeexplore.ieee.org/document/8863351?denied= In the link above you can read one of the latest articles about finding the shortest path and understand the application of graphs in them. Secondly, In every country’s banking system, there exists a team that has a list of all transactions and they should recognize high-risk transactions or even money laundering. In fact, by modeling transactions to graphs and using the common methods of finding patterns which are in many articles like below, they can find abnormal transactions with good accuracy. Additionally, we use these graphical patterns to recognize frauds in mobile networks.

https://we-yun.com/doc/neo4j-book/%E5%9B%BE%E6%95%B0%E6%8D%AE%E5%BA%93%E4%BA%94%E5%A4%A7%E5%BA%94%E7%94%A8%E6%A1%88%E4%BE%8B/Fraud%20Detection%20Using%20GraphDB%20-%202014.pdf

Thirdly, in data mining, there are many combinatorial algorithms for example streams are mostly commentarial algorithms such as uniform sampling or even more famous ones like Flajolet, DGIM or ASM. https://www.sciencedirect.com/science/article/pii/0022000085900418 or https://www.sciencedirect.com/science/article/pii/S0022000097915452/pdf?md5=a1d6b653f215655121004757d1e18a4f&pid=1-s2.0-S0022000097915452-main.pdf&_valck=1 Fourthly, you can see a wide range of usage of prediction and estimation in machine learnings. There is about no article that doesn’t talk about the probabilistic proofs in part of it. We should consider that this probability is not normally the probability that we see in olympiads but it’s a more advanced version. Also, lots of proofs and definitions in machine learnings are by using combinatorics such as VC-dimension of many sets, Rademacher complexity and sign rank are proved by combinatorics directly, in many cases. https://arxiv.org/abs/2007.11045 Fifthly, in some cases of optimizations, some combinatorial algorithms help for example in distributed optimization, I have seen many articles about calculating SGD which are using coding or random algorithm to have calculations with lower errors. For example, the following article finds an algorithm for SGD which uses a well-known Coupon Collector problem. https://ieeexplore.ieee.org/abstract/document/8425504/

Of course, Combinatorics and Combinatorial ideas have usages in some other parts such as Verne style cryptographic algorithms, distributed computation or coded computation, safe computation.

Thanks for sharing such great resources, lot to learn.

First, I think we can discuss about this. The blog post implying that we can register in competition in order to improve combinatorics skills, so then we can understand "how scientists are improving artificial intelligence".

As combinatorics in "Iranian Combinatorics Olympiad", we are talking about

purecombinatorics, notpracticalone. For example, in "recognizing high-risk transactions or money laundering", there is a practical application of combinatorics to "find abnormal patterns in graph". It is nessercary to know combinatorics in order to understand basic idea of "find abnormal patterns in graph", but it is not sufficient for "recognizing high-risk transactions or money laundering".So I am suggesting that "if you almost know how to "build navigators to find the fastest way to your destination in a crowded city", you can understand it better if you improve your combinatorics skills." (but in order to "build one", there are lots of topics even outside of mathematics you need to learn)

At last I think there should be a formal definition of combinatorics olympiad in website, before advertising here. Codeforces considers combinatorics as problems referred to some sort of counting or choosing. Something like finding shortest path in weighted graph includes other topics like graphs too.

What time is it on the contest day, or is it a 24h contest format? Should we assume access to computers (writing a dp etc to verify answers/guesses is fine), or not?

Hi there, The contest is on 30th of July at 4:30(UTC). The duration of the exam will be 5 hours for advanced and free levels and 2 hours for elementary. You can use algorithms and dp for guessing but obviously you can not refer to it in the proves.

Just to check, this is the timing of the contest? It is on a Thursday/Friday?

Hi The contest is on Friday 30th of July only. The starting time will be at 4:30UTC If you are in grade 10 or higher the duration of the contest will be 5 hours for you!!

I am just wondering why the competition falls on a weekday. I think most people who have not graduated will be in school when the competion is live. Because of this I am unfortunately unable to take part :<

Well, actually the contest is on weekends in our own country. In Iran our weekends are Fridays and Thursdays. I am sorry to hear that you can't participate but please let me know if I can help you!!

Oh that is interesting!

I cant believe I have lived so long without knowing that many countries have work weeks that are not Monday to Friday :|

How is question pattern of ICO? I mean, is it just combinatorics problems to prove something? I am participating for the first time and I don't know these....

ICO2020 was a great one. Hope to gather a medal this year!

So excited to see ICO coming back! ICO 2020 was a great experience. I really enjoyed participating in the contest with you, and of course, winning a medal together. As mentioned by others, the online standings was a new, unique and exciting experience which could not have become true without fast, knowledgeable and experienced graders. It was the brilliant and innovative point in the contest. I am looking forward to participating in ICO 2021.

Is there any limit on how many teams from each category can register from each country?

No, there is not!!

Hi I would also suggest posting this on AoPS(if you've done this already, could you give a link?) as more people would be interested there I belive.

Hi Thanks for your suggestion and yes I have posted it in the AoPS and will share the link with you right here AoPS Link I hope you can share them with more people and ask them to take part in our competition.

Thanks! Sure, I will try to do that!

JUST WANNA ANNOUNCE THAT THE DEADLINE TO REGISTER IS 24TH OF JULY SO IF ANYONE ELSE WANNA PARTICIPATE PLEASE HURRY UP...

in math olympiads, combinatorics refer to anything that is not number theory, algebra or geometry, so that is almost all codeforces problems

Are the problems already available somewhere?

The booklet of the ICO2020 is available at the ico-official.com and the booklet of the ICO 2021 will be published soon(as well as the editorial for the full proof problems)