Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos.
Educational Codeforces Round 195 (Rated for Div. 2) will start on Oct/14/2026 17:35 (Moscow time).
This round will be rated for the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given 7 problems and 2 hours to solve them. I hope everyone participating finds interesting problems for them to solve.
The round is based on the problems from The ICPC Southern and Volga Russia Regional Contest. If you participated in the Qualification Stage, please refrain from taking part in this round.
The problems were prepared by fcspartakm, Roms and me.
I would like to express my gratitude to Mike MikeMirzayanov Mirzayanov for creating Codeforces and Polygon, two platforms which made conducting programming contests and preparing problems for them much more convenient. Also big thanks to testers: awoo, FelixArg.
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Good luck!
Planned post contest discussion stream here
Good luck to everyone, specially to @TheBlueVoid, @guinelo_cp and @-robby-, the best competitive programmers here in Parintins — Amazonas, Brazil.
Good luck to you too my friend. I hope i reach specialist in this contest!
I hope I can manage to do the contest, since I have a guitar lesson :(. I’ve already missed classes for the course because I was doing another contest. Good luck, everyone.
Good.
lets go, another contest! gonna have fun
Everytime I give edu round I always get negative delta. :(
Max positive delta that I ever got from a Edu round was +3
finally one i can participate in without having my schedule blown up
Does unrated registration not exist anymore? I don't feel like competing with AI bots.
I would also like to participate unrated but the option still does not seem to exist.
Why is there no option to register unrated?
I don't feel like competing with low rated users.
said by a newbie
Gimmick comment. Read his username
we are all a newbie in something
Is the given test case for problem D wrong? Cuz it doesnt seem to validate the ps
no see, there are 3 vertex , and only one edge between 1 and 2
vertex 3 does not have any neighbours ,it doesn't have at least one neighbour to be the opposite color
yeah 1,2 and 3 were fine. but what about the 4th test case
1->2->3->4. shouldnt the answer for this be 2.
cuz as far as I can understand the only ways of valid coloring are R,B,R,B and B,R,B,R
Nope , it can also be RBBR and BRRB.
Ooooo yeahh, Ig I was too biased towards bipartite after reading the question. thnx for pointing that out thouu
RBBR and BRRB is ok as well, it's already enough for each vertex to have just one neighbour with a different colour, and it’s no need to let all neighbours be different.
1st Educational round :) !!
The problems were definitely tricky and good as compared to normal rounds, which explains why people say Edu rounds are tricky and heavily rely on paper solving.
Loved the clean problem statements though disguising the math behind fun themes like 'Caveman' made it super engaging. F was Red Flag for me uff Game Theory with Alice and Bob tf :skull
Thanks to the writers for such a round!!
F is amazing
I thought E was a really nice problem but I agree C was not very fun. D was also kinda meh and felt kinda cheesy.
In F, if there is one (k+1) element isn't the goal to leave bob with exactly one (k+1) element and a bunch of (1s) whose frequency is divisible by k+1
Oh boy do I LOVEEEE speedforces slop...
I love educational contests!
i absolutely bombed this contest .... i figured 0_1 and 1_0 will do nothing but then i wasted 1 hour on B just to notice that cases of 111 and 000 along with 01 and 10 are reduntant :(
unfun E and F :(
seems every AK users are cheaters :clown-face:
Thanks to the authors and testers! The problems were really good and enjoyable to solve.
What kind of leetcode ahh contest was this. Also insane amount of cheaters I feel like.
I think F was more like an Atcoder problem
First A-D I've ever gotten!
Same
Same :D, congrats!
Very bad contest imo.
A–E are way too easy, but the gap between E and F is just insane.
I feel like this would be better as some kind of Blitz Round, since the results don't really reflect people's actual skill level.
speed correlates with skill pretty well fyi
ratiod by bocchi
I get that, but I think rating should mostly reflect your problem-solving skills rather than how fast you can solve problems. Of course, speed matters too, but it shouldn't have such a huge impact on your rating. In this contest, 1000+ people solved A–E, which says a lot about the problemset and its balance.
Screencast with commentary
Thanks man for F and G ideas as well as explanation..
I’ll probably lose rating, but I actually enjoyed the problems. They required a good understanding of theory, which is my favorite kind of contest. However, I have one suggestion: consider adding hidden prompts to detect AI-assisted cheating or implementing a more effective anti-cheating system. I feel like easier contests tend to have more cheaters because AI can solve those problems more easily and the main reason for some who didnt like the contest is that. Honestly, I think my rank doesn’t really reflect my performance in this contest. BTW thanks for the contest :)
Please look into this, submission
It seems like the judger is down and it stucks the sys test like forever QAQ.
A-E felt more like a Div. 3
Problems A-E seemed to be pretty easy to reason about. C probably was the simplest in this set. Liked B and D though.
Education Round 195 be like
A – E: Speedforces
F & G: Stopforces
BledDest, could you restart a submission which is currently blocking the system test from completing? Practice submissions are still not allowed.
E is really a trash problem.I think I will meet it in Atcoder Beginner Contest E.And the order of the questions seems to be random.Maybe It's not a good round.
I tried my best but can't solve F :(
C is also too standard. A standard Atcoder Beginner Contest 300 score problem.
It is like a LeetCode medium at best.
I can't understand why my answer to pB is correct. I just guess it after 1 hour to the contest. pC is easier to me. I can't solve pD as well...
If you change a substr 101 to 111 or change a substr 010 to 000 then overall size of the final string will be decremented by 2. For example, take 001011. if step 1 not done, final string will be 0101 but if it's changed to 000011 in step 1 then final str will be 01. Note the difference bw 0101 and 01
Similary, If you change a substr 111 to 101 or change a substr 000 to 010 then overall size of the final string will be incremented by 2
Changing the final string size by 1,3,4,5,6... is impossible cuz:
to change by 1, u need to either insert a new maximal block or delete an entire maximal block, which is impossible
to change by more than 2, u need to change at least 2 digits but problem statement allows a maximum of 1 digit change only
Hence, only:
performing no change is allowed (1 in ur code)
incrementing final size by 2 is allowed (b in ur code)
decrementing final size by 2 is allowed (c in ur code)
split the problem into the following cases:
2.1. 2
2.2. Many
B: The compressed string is always alternating. Its first and the last characters are fixed so a different compressed string corresponds to different lengths. In one operation, you can change the length by 0 or by +/- 2. Therefore, the answer never exceeds 3. Now, if there exists 010 or 101, then you can flip the middle bit and reduce the compressed length by 2. If there exists 111 or 000, then you can flip the middle bit and increase the compressed length by 2.
D: Notice, that the answer is never 1. Now, if some node is isolated, it never has a neighbour to begin with let alone one with a different colour. So, return -1 in this case. Next, split the graph into minimum sized stars (this is always possible). If there is only 1 star, then the answer is 2, otherwise > 2. You do not need to simulate the splits. Just determine if the graph is a star or not.
I see, I missed that a star's answer is 2. Really thanks for your comment .
For D, another way is:
Brain melt: if there is an isolated vertex
Many: if there is a cycle, or there is a simple path having ≥ 3 edges, or there are atleast 2 disconnected components.
2: otherwise
For many case:
1. Cycle: can be done using DFS/BFS
2. Simple path of ≥ 3 edges: pretty simple algorithm where for a path A-B-C-D, you loop through all possible edges B-C and see whether distinct A and D exist.
3. Atleast 2 disconnected components: Again using DFS/BSF.
There's only one special case which is of a triangle. But, even that has more than 2 colour schemes.
i think the core observations were necesarry in this p, it seems like u have to write it down for diff cases and see the implicaitons of the constraint. like the obs that for all strings of same length will be same, is a imp nice obs, which happens because of guaranteed alternate strings. so my q is, sometimes these problems can only be dealt with via good obseravtions and writing diff things down ryt
Is the system testing finished?
Do you know when the rating will be updated?
When will the rating be updated?
Weak test cases on Problem B (allows O(N^2) to pass). Please correct me, if I'm wrong.
My submission is O(N^2) in worst case, still passed in ~170 ms.
Hello Codeforces team,
I am the author of submission 394572504 for problem 2276E and received a similarity warning for that. I wrote this solution independently and did not share code with or receive code from any of the listed participants during the contest.
I regularly store my Codeforces solutions in a GitHub repository. I do not publish codes while the contest was running and publish them only after the contest had finished:
https://github.com/manhhomienbienthuy/codeforces
The repository contains my commit history and reflects my established coding style and workflow. I can also provide the relevant commit details, local file history, earlier versions, and an explanation of how I derived the solution if needed.
I respectfully request that this case be reviewed. Thank you.
P.S. I reviewed other solutions in the list. Although there are common ideas for the solution, the codes are different.
Hello Codeforces team and contest coordinators,
I am requesting a manual review of my submission for problem 2276D (Caveman) from Educational Codeforces Round 195, held on 14 October 2026.
My submission ID is 394583640, and the warning references submission 394568273 by user SHIKARI26. I do not know this user.
I independently worked out and wrote my solution in VS Code. I was surprised to receive a warning stating that my submission significantly coincides with another user's code.
It has now been five days, and all four of my contest submissions are still marked as “Skipped.” My profile continues to show a rank of 2496 and a rating change of +72. I can still log in, register for contests, and submit practice problems, but I do not know whether my contest results have been finalized or whether any further action is pending.
I understand the importance of maintaining fair competition on Codeforces. I respectfully request that the relevant submissions and my contest status be reviewed manually. I am willing to provide any available evidence of my development process and explain my solution if needed.
Thank you for your time and consideration.
Subject: Request to review disabled account (handle: kavyasanger) – skipped submissions
Hello Codeforces Team,
My account kavyasanger (email: [email protected]) has been disabled, and I would like to request a manual review.
In my recent contests, my submissions were marked as Skipped. I believe this was a mistake, for these reasons:
A flagged contest where I made no submission. In ED round 195, I did not submit any solution, yet that contest was also flagged on my account. I can’t see how a contest with no submissions could involve any violation. The problems I solved were simple. In the other flagged contests, the problems I solved were straightforward, low-rated ones. They use standard approaches, and I am fully capable of solving them on my own. Because the solutions are short and common, similar code from other participants is natural. I have not cheated. I did not share my code, and I did not use anyone else’s solutions. I write my solutions myself in C++, in a plain, simple style.
I have been an active participant for a long time and want to keep competing fairly. I’m happy to explain my approach to any of these problems, or to provide any other information you need.
Could you please review my account and, if the flags were a mistake, restore my account and my skipped submissions?
Thank you for your time.
Regards, Kavya Codeforces handle: kavyasanger Email: [email protected]