Hi everyone! Codeforces Month Of Blog Posts Pt. II has ended at 15th of November. Sorry for the delay of the results!

Overall, we (together with orz and i_love_penguins) raffled $800! I've chosen 6 blogs to be named winners, and here they are: TeaTime, Iura_Shch, asdasdqwer, WeakestTopology, catalystgma win $150 each and valeriu wins $50, congrats!

Here are the links and brief reviews of each winner blogs!

• TeaTime – Counting Perfect Matchings – won 150 usd! – interesting read, loved it! The described algorithm lets you count the number of perfect matchings in a bipartite planar graph in $$$O(n^3)$$$. Proofs are understandable, the blog is of high quality, not sure about the applications though :D
• Iura_Shch — Online 3D Mo's algorithm – won 150 usd! – interesting idea! Briefly, to answer subrange queries you split the $$$N*N$$$ grid into $$$C * C$$$ blocks, so you can update your struct in $$$O(C^2)$$$ and answer the queries in $$$O(\frac{N}{C})$$$. By choosing $$$C$$$ equal to $$$cbrt(N)$$$ you can get the something like $$$O(N^{5/3})$$$. Basically, the asymtotics is the same as in regular 3D Mo's algo, but now it supports online queries! (but uses additional memory :])
• asdasdqwer – Rotating Calipers and It's Applications (both parts) – won $150! – a blog about the rotating calipers technique with a lot of nice pictures and explanations. Also, a lot of applications – it turned out I didn't know most of them!
• catalystgma – Exponential Length Substrings in Pattern Matching – won $150! – a nice blog with an interesting idea and A TON of proofs :)
• WeakestTopology – Snapshot of finite calculus and using it to solve a 3000 rated problem & The discrete derivative, falling factorials and polynomials – won 150 usd! – it is a nice introduction to the finite calculus! I loved the first blog, my inner mathematician is happy. As for the second blog, I was able to read only the first half of it, so can't really tell it's quality haha
• valeriu – Heigh-wise Small-to-large trick – won 50 usd! – classical/basic idea, but still a nice blog, make sure to read it if you don't know the trick!

Sorry for those who wasn't able to win this time! Make sure to check out every blog in the comment section of the announcement!

Thanks everyone for taking part in the challenge! Hope you liked it :D

TL;DR: Post an interesting Codeforces blog until October 15th and win $800+1.

UPD: We decided to shift the deadline to 15th of November!

This blog is inspired by peltorator's Codeforces Month of Blog Posts.

Hi everyone! The last time, this initiative was a gem for me! I've enjoyed every bit of it and the winner in particular — it helped me when I needed it the most. So now I willing to pay back (or forward :D) — by organizing the Codeforces Month of Blog Posts one more time!

Intro

My view is the same as peltorator's one — I am a huge Codeforces fan, it almost replaces me social media, and the blogs section is one of the best parts of it! Many people may be waiting for the best time to publish their blogs — now the time has come!

Rules & Deadlines

The rules are simple:

1. Post something on Codeforces not earlier than 10th of September (00:02 UTC) 2024

We are looking for novel ideas / new views on the topics / tutorials on the topics that we have not seen yet — anything of your choice. It could even be somthing like this comment! — I think you get the idea: write something novel. If I were to judge, one of the best post of the previous peltorator's months was probably his own announcement :D

2. Send me a personal message until 15th of November (00:02 UTC) 2024 with the link to your codeforces blog post

I would appreciate it if you also include a one-sentence explanation at the beginning of your blog post explaining this challenge and a link to the blog post you are reading right now so that more people can learn about it and participate. So the general deadline is 15th of October.

Prizes!

The winner blog post will be awarded with a money prize — $350+1! The runner-up will win $250! The third place will win $150! The forth place will win $50! :)

If you are willing to increase the budget for the winners — also PM me :D

The process of choosing the winner is not decided yet, I may think of two ways: choosing the winner by myself, or the blog post with the most amount of likes. Write your own opinion in the comments sections

Outro

Let the challenge begin! I hope there will be at least one great blog, so my initative won't be left useless :D

801$ is not a small amount — so I believe in you, make something novel, make something that people want!

Maybe we should hold this sort of thing annually? Something like "Codeforces Year of Blog Posts"? Write our ideas in the comments section!

P.S: Check out LI2 Contests!

UPD1: A great friend of mine decided to give an additional $200 for the runner-up! He insisted on remaining anonymous though D:

UPD2: One month left! Additionally, let's thank i_love_penguins for giving a $100 prize for the third place

UPD2: One month left! Additionally, let's thank orz for increasing the budget by $200!

Hi everyone!

I'm thrilled to invite you to the LI2 Contest — free collection of high-quality contests to master every topic — here, on Codeforces! Group Link! Click here!

Current avialibale list of topics:

Loops; Prefix Sums; Sortings; Binary Search; Recursion; Sweepline; Two Pointers; Linear Data Structers (stack, queue, etc); Graphs, DFS, BFS; Dynamic Programming; DSU; Shortest Paths; Minimum Spanning Tree; Greedy; ...

Why this course?

I believe that finding high-quality problems is the hardest part of practice, especially when you are only getting your feet wet with competitive programming.

There are many lectures and articles, but not so many open collections of problems for each topic.

Time-tested

I guarantee you that this course is time-tested, I used it myself.

LI2 is short for Boarding Lyceum №2 in Kazan — the school I study in. So we've been using this course for years and I can proudly say that we are one of the best schools for studying informatics in Russia, alongside with several other schools in Kazan, Chelyabinsk, Moscow and St. Petersburg.

Some notable people that completed the course from our school are: bashkort, Nutella3000, asafiul, isirazeev, M_bolshakov, Rip_robot, nocap, Pavarishko, lishy2 and many many more!

How To Practise Competitive Programming — The Russian Way

There are two main "How To Practise Competitive Programming" blogs that I really love: Radewoosh's and Um_nik's.

I agree with them both, but want to present the other way that is used in Russia. So here's a brief carrer of a competitive programmer in Russia:

1. Get into a great school (optional, but much recommended)
2. Start doing CP in school and/or at weekly held lectures + contests sponsored by big tech companies (like Yandex & Tinkoff)
3. Attend CP camps in Sirius or camps like SIS — Summer Informatics School.
4. Solve problems provided by these camps and tech companies
5. Win a prize medal at the Russian OI
6. Go to any university you want

As you see, almost all of them are very lucky that they have mentors who provide them high-quality contests. They don't have to worry about what problems to solve. Believe me, I'm an IOI gold medalist from Russia and know the system extremely well.

And these contests (in the LI2 group) are taken from the camps mentioned above, isn't it great?

As a side note, if you don't want your problem to be here, please, contact me right away. To be honest, I believe that they are not kept in secret since everyone in Russia knows them, but still, if you have any disagreement with me sharing your problems — PM me.

Announcement and Discussion For Each Contest

There's an announcement for each contest in the group's blog section. In the blog you will find lectures & artices suggested by me, as well as disucussion in the comment secion under every blog, where you can help each other!

Articles and Lectures include links to pashka's youtube lectures, usaco.guide articles and some cp-algorithms.com articles.

I believe that usaco.guide is one of the best, if not the best, place to study algorithms and solve problems. But I don't see any problem in using both usaco.guide and this course, the more the better!

Additional Practise

But let's be honest, you won't get anywhere without additional practise. It can be codeforces contest or previous olympiads. When I started completing the course, I was practising on past Russian olympiads. Without them I wouldn't get anywhere. So you also need to find other ways to practise additionally not just topic-based contests. Codeforces Rounds are a great way to practise!

For reference, this is my raiting graph when I started completing the course:

What to do now?

Get into the group by clickling on this link. Solve the problems and get better, share the group with your friends!

If you have any suggestions, please, let me know in the comments!

Thanks!

I didn't make the course myself, I only translalted it and published it.

1. Huge thanks to MikeMirzayanov for making this hole thing possible!
2. Huge thanks to ilsaf13, the informatics teacher in our school, for maintaining this hole thing and helping us with our CP journey!
3. All of the people who prepared problems over the years!

Hello everyone! As you might know, IOI 2023 will start at the 28-th of August in Szeged. Let's share your predictions here!