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!