Hello, Codeforces!
I am super excited to invite you to participate in Codeforces Round 1096 (Div. 3), which will take place on Apr/30/2026 17:35 (Moscow time). You will be given $$$2$$$ hours and $$$30$$$ minutes to solve $$$8$$$ problems. All problems were authored and prepared by me.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of 10 minutes for each wrong submission, following the rules of educational rounds.
Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:
- take part in at least five rated rounds (and solve at least one problem in each of them)
- do not have a rating of 1900 or higher at any moment in time.
Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you (unless you register unrated).
I would like to thank the following people for making this round possible:
- cry for coordinating the round;
- __baozii__ for red testing;
- -firefly-, omsincoconut for orange testing;
- cgmoreda, SpyrosAliv, wuhudsm, Argentum47 for purple testing;
- mathtsai, chromate00 (VIP), Mousa for blue testing;
- simplelife for cyan testing;
- lina_os, Syrianooo for green testing;
- Vladosiya for statement translation and testing;
- MikeMirzayanov for developing Codeforces and Polygon.
Good luck, and most importantly, have fun!
So excited
As a member of the Sunphis fan club, hope I become an expert.
As a VIP participant of cf rounds,I've fully prepared to solve div3 problems.
ying is ready to ak
Finally after months!!!
The best, as usual
why isnt carrot working in recent contest? Can something be done about it?
Actually Codeforces' API, from where Carrot fetches data, is down since a few days, more than 21 days to be precise, we can just hope it gets fixed, the same thing has happened in past too.
We can try doing this
this is my last chance to become an expert before my finals
I hope I get a plus in this contest.
Wish my friends wwwqwq,whopassby,yiren and mikasa_kira can improve their rating this round
I'm a super fan of Kuro_neko!
Mandatory Comment
hope to AK the round and get back to my peak!
I am ready to participate in this contest.
Me too...
Hope to reach specialist level in this contest. Let's gooooo
best wishes
kskbl？
HELLO
Hoping for some Interactive Problem:)
Don`t trust pretests this round.
Open hacking phase will likely change final standings significantly.
someone call me when the contest starts +78129254848, i'm going to take a nap
As long as I call your phone, I will receive a billing notice shortly, because we are in different countries.
my first contest, super excited!
10/10 experience
ye greater contest div 3 of all time
yep!!
pupil
excited
Will participate in a round after 1.5 years.
_nsa_is a cheater, he cheats at every contest using AIMikeMirzayanov, ban him
xD
79XD
Hello everyone, my account is disabled by adminstrator by no reason, and I did not get any notification. What do I need to do? Can anyone help me please to get my account back. In my own account I am Candidate Master, so I need that account
codeforces
speedforces
чо
Div. 4 pretending to be a div. 3 :)
Interesting problems! My first All Clear cooked by greedy in H
so is it greedy or not? mine didn't work
I think that also need re-rooting
Best Div 3 of the year?
It All Went Sideways (my rank on the number line) after seeing the problem E.
Prefsum-forces
Can someone tell me what's wrong with my solution to problem D? https://codeforces.me/contest/2227/submission/373151513
Can't understand your code... what's your idea?
the same as the editoral
I think you are calculating mex3 without checking if the [i..j] is palindrome where i<j and A[i]=A[j]=0
Ohh Okay... Now as I read the editorial, my solution is completely different from it and completely relies on the nature of the given data.
I basically just started expanding palindrome of even and odd length and insert the given elements into a set, once I have a palindrome of a fixed length i just check which element is missing and that is my mex and then I update the answer. The only reason why it work is because there can be at most two duplicate number thus the inner and outer loop will consider an element at most 4 times. So it is sort of O(4n)
You have to have the loop for finding mex3 inside if(palin) block. Else you might not have palindrome in l to r (as also mentioned by vanshgambhir) but still have updated some values in Esta3 vector.
Accepted
You messed up with brackets. Look carefully though you are expanding on outer end when inner subarray is palindrome but you calculate mex3 regardless of if inner is palindrome or not. Just shift your for loop inside if(palin) block and it should work fine.
H is a really cool problem, but how to solve G? Really good contest, thanks to authors
For segment ending in odd index, the sum on odd index has to be > sum of even index and vice versa
I got so lucky to guess the invariant in $$$G$$$! and then it was just a simple counting problem after that.
Bruhh
I really liked the problemset
Thanks for bringing to my attention the Egyptian Koshari dish, I will try!
is this contest easy or its just people with AI made the standard of this contest lower ? or am i noob ?
You're right, it's on the easier side for a Div. 3
Very nice problems!
hello world
although I only solved A,B,C . it was a good contest ! hope I make it in the next few rounds ISA
Problem authors definitely made the hacking interesting this round. Having a lot of fun!
It isn't... For me...
I got +11 on D, and now it becomes -12.
wonderful contest, fun problem without mind boggling math tricks and complex data structure.the best div3 and wish more nice contest like this
uhh how long would it take for changes in rating
It was a great contest!
great contest,but the sample explanation of C has some mistakes
In how much time will results get announced??
A few hours after open hacking ends
It was my first contest in almost a year , felt afetr solving 3 problems
Doubt: When will the rating change happen if at all there is?
It takes a while. Rating updates a few hours after open hacking ends.
Hi, this contest appears unrated in my profile, is it because of the C problem statement correction? Can anyone help me with this?
Because the rating hasn't be updated.
I think that you should wait patiently.
Thanks a lot, I feel relieved. I haven't used cf much so I was in doubt.
on no I missed it AGAAIINNN
I'm new here. Wanna ask if this competition doesn't have a rating, right? What should I play if I wanna improve my rating?
This contest will be rated some hours later. Don't worry, most of contests are rated.
i did'nt got rating why this is my first contest
You may have registered as unrated before the contest started
good experience
Hey, I just had given 4 contests and this was my 5th one, and I got a rating jump, while I think the contest must be unrated for me. Can anyone help me
From the contest announcement:
Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you (unless you register unrated).
I love this contest. ANd I got 370 ratings. And problems are very interesting and exciting for me. I love all.
Hello,
I received a warning that my solution is similar to others in this round.
I want to clarify that I solved the problem on my own during the contest. I did not copy any code or communicate with anyone.
My solution comes from my own understanding of the problem. I wrote the code from scratch and followed my usual way of solving problems.
I understand that similar solutions can happen, especially when the idea is common, but my work was completely independent.
If needed, I can explain my solution step by step.
Thank you.
Hi,
I received the plagiarism warning for my submission for problem G, and all of my submissions in the contest are marked skipped. I would like to clarify that I did not intentionally copy anyone’s solution. I solved the problem independently and had no intention of violating the contest rules.
Unfortunately, I do not have editor history or other proof saved that could clearly demonstrate my solving process. I understand the seriousness of this matter and respect the efforts taken to maintain fairness in contests.
I am not trying to argue with the system; I simply wanted to honestly state my side.
Thank you for your time.
good