I'm not a fan of learning complex topics in CP. I prefer practicing the things I already know, or practicing by rating, not topic.
The problem is that, now that I'm preparing for EJOI, I have no idea if the basics will suffice, especially considering other people born after 2011 who will go to EJOI.
So what are the topics that you HAVE to know if you're going to EJOI? Also, are interactives/grader problems a thing in EJOI?
Thank you, and best of luck to everyone preparing for EJOI
https://2025.ejoi.org/syllabus/
Also, are interactives/grader problems a thing in EJOI?
Yes
Thanks a LOT, man! This is huge for me!
There might also be communication problems, and although there weren't output-only problems in EJOI 2025 there were in IOI, BOI and JBOI, so I think there's a high chance that there will be in EJOI 2026 as well. Check out this problem from the practice round of IOI 2025 (Part II is output-only)
Well, communication isn't as bad as graders, and interactive problems
None of them are very bad if you practice. They can be much easier o harder than batch problems. (In fact, the most-solved problem of IOI was interactive and (I think) with functions)
Btw, I recently made a powerpoint on problem types, you can find it here.
Tysm, this will help my with my hate towards grader/interactive
No problem! Feel free to message me if you have any questions
Alright
Aren't they a new style of questions or are they newly adopted here in codeforces??
They're a recent addition in codeforces but there have been communication / output only problems in OIs for years
“You need to know the Tree topics.”
That's fine
EJOI places great emphasis on data structures, especially segment trees. Graphs / trees are very important too. There are very few (non-interactive + ad-hoc) problems, so it's very different in nature than codeforces.
Wait so it's mostly interactive? Oh no... ;-;
I'm good at graphs, trees and not bad at seg tree but very bad at interactive, and graders
Every year there are around 1-2 interactive / grader problems out of 6. What I meant earlier was that the problems are often classic, not observation-heavy.
Oh, alright. Thanks, a lot!
I'd say mastering segment tree and basic tree stuff like binary jumping lca etc is enough. Contest strategy is also probably different since it is 4 hours unlike other contests. You can do virtual contests on your own to practice :)
Ah, alright! Thanks a whole lot, man
PieArmy orz
Good luck
Most advanced thing I used to get gold in 2025 was an ordered set. Problems last year were focused less on data structures (which is weird for EJOI). In all cases learn everything from syllabus but be ready for constructive and observation heavy problems.