Привет, Codeforces!
Благодаря поддержке Neapolis University Pafos, продолжается серия образовательных раундов.
В 14.11.2025 17:35 (Московское время) состоится Educational Codeforces Round 184 (Rated for Div. 2).
Этот раунд будет рейтинговым для участников с рейтингом менее 2100. Соревнование будет проводиться по немного расширенным правилам ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением, равен 10 минутам. После окончания раунда будет период времени длительностью в 12 часов, в течение которого вы можете попробовать взломать абсолютно любое решение (в том числе свое). Причем исходный код будет предоставлен не только для чтения, но и для копирования.
Вам будет предложено 6 или 7 задач на 2 часа. Мы надеемся, что вам они покажутся интересными.
Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Иван BledDest Андросов, Максим Neon Мещеряков, Роман Roms Глазов и Максим FelixArg Новоточинов. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.
Удачи в раунде! Успешных решений!
UPD: Разбор опубликован
Hope to reach expert again with this contest.
i trust u.
thx
are you gonna reach expert?
check my profile around 14 hours later and find out.
you became Expert and i became Specialist :)
Congrats
Hope to finally hack LonggVuz
nah, u won't have a chance hehehe :D
But at least i will try.
could you?
:((( How you doing that strong codes? I can't find edge case to any of your codes, they are too strong. Ok, you win a war, thats your gold, don't kill me:
There should be a goldlinux ahh pfp
(i used to use garuda linux btw)
actually he is call tux :NerdFace:
bru
hoping +delta
Could you please add the score distribution :)
in edu rounds there is no score distribution It is like div3 and div4.
there is no score distribution in educational contests
I hope to solve atleast a single question. :)
bro,you have solved 88 problem of course you can solve more than 1 problem ,best of luck
I hope so :( ! most of the problems I solved are 800 rating :haha .
Hope to solve at least 3 problems, thus increase my rating.
Long time no see
Hope we will have a good night with this round.
It is not going to be good till we don't get rating changes
Come on, brother!
May I ask who can tell me the difficulty of this competition plz orzorz
"6 or 7 problems"
6 7
WHY UNRATED ALLOWED???
Is the contest delayed?
yeah timer keep reseting to 10 minutes .. 2 times now for me ... aaaahhh !!!
Am I the only one for whom the contest hasn't started ??
Why is it getting delayed over and over again?
I don't know if it's a glitch or not , but whenever i am refreshing my website its showing that contest will start after 11 min 6 seconds. I am not able to enter in the contest even though i have registered in this contest.
whoa !! does this mean different people see different timer LOL
it's 11:06 for me at tho :(
no I understand ( same for me ) ... do we like not refersh and then it will start or what LOL ... education for patience
At least they must just update the final timing , then I won't miss my dinner :(
yeah !!! The official announcement / update will help
Same here
so what is the actual time ?
Contest had already started for so many people , this glitch is only for some people.
no panic !!!
What happened to Codeforces? ;((
weird .. I tried entering the contest but couldn't the timer refreshed again and again ..
and then I entered, and looks like I am late, others have already made submissions :cry
But your submissions don't show todays contest
yes, I haven't made any submissions yet, as I got late because of this timer glitch ..
but I can see standings and the number of submissions others have made to a specific problem ...
is it just me or does the timer keep refreshing on the 11th minute?
same for me.... I have left one page where I will not refresh and let the timer go to zero .... we will see what happens
The contest seems to be working from m1.codeforces.com but keeps getting delayed in the main page. I found that out 15 minutes into the contest. What a waste of time, now I cannot answer the contest as that would lower my rating.
I guess you can submit... with very high probability ( coz many people facing issues ) .. this round might end up unrated .. but if you don't want to take risk that is OK !!
The same thing happens when I don't log in or access it via mobile. What is this?
ok now suddenly it says
contest is runningand I can see the problems ..This round should be unrated.
It will be unrated, it has to be
Why? Those who couldn’t enter couldn’t submit anything.
it seems, it started at different time for different people, so possible that many people started late and they didn't know others started earlier.
like people were getting their start timer reset to
11.06on refresh as mentioned in other comments and were not entering the contest at the scheduled time ( I faced this too )Obviously it should be
honestly , the 11:06 is so irritating and I'm so late that I gave up the contest ╯︿╰
I was looking forward to reaching the specialist rank today, but unfortunately the contest started and I couldn't participate because Codeforces kept saying 'starts in 10 minutes'. gg :(
contest submission page is also misbehaving for me ( not showing latest submissions )
[workaround] .. so I am able to see updated status on personal submission page on my main profile submission
when I submitted B , my C was still running :(
oh sorry I don't understand.. you mean
ya ya (kind of) , participated from m1.codeforces.com :(
ok didn't face this issue... I think you solved B very quickly for this to happen ha ha !!
I don't like this round
LOL!!!
now contest remaining time also shows different value on different pages,
after refreshing them now
25minremaining4minremaining55 minremainingI think some issue with timer of codeforces today LOL .. I am on main codeforces site and not a mirror
one of the least enjoyable contests in recent memory
That sigh of relief after having solved D2 and D1 simultaneously in the last 5 minutes !!
UGH D2 TLE on test 27
D2 TLE on testcase 27 :sob:
round was not good in overall experience,
I hope this doesn't happen on Sunday, as I cancel some of my outdoor activity to make time for this
What is the reason to reject binary search solution in D2 =(
With some optimizations binary search works just fine: 349019338
I guess it is not enough with just some optimizations
After hacking phase and retesting my initial solution went from 1.3s to 4.6s.
But I was still able to optimize it from 4.6s down to 1.64s :) 349375791
Can anyone give some advice for C?
I guess we need to solve (l+r)*(r-l+1)>prefix[r]-pre[l-1] but I couldnt figure out the implementation part in the given time, will have to upsolve.
yes close...
we can convert this equation to a form where
landrare having similar expression then we can solve it in one iteration left to right ... the expression isi*i + i - prefixSum[i]for indexiyes , try expressing out best gain we can achieve from a segment as best(l,r) = (r-l+1) *(l+r+2) , equate out the l and r terms seperately and we will get two identity equation for every index i, depending on to take it as L or R , just try to maximise those two terms
there is also this mysterious idea ... mention here https://mirror.codeforces.com/blog/entry/148317?#comment-1325552
interesting one ,thanks
lmao after seeing your variable name in problem C :)
We all love it (first thing it comes in my mind when I am stuck in a problem , /s )
I was also able to figure this out but was unable to reach final solution :(
For a fixed $$$l$$$, we need to calculate
So you can just precalculate $$$[r^2 + r + s_{r+1}]$$$ values and their suffix max, then iterate over all $$$l$$$ and calculate the value for each.
Nice!
thanks! will try now
The nice solution: consider the sequence $$$b_k = a_k - 2k$$$. Note that the sum $$$\sum_k a_k$$$ which we wish to maximise is equal to $$$n(n+1) + \sum_k b_k$$$ and that setting an interval $$$a_l, a_r$$$ to $$$l+r$$$ is equivalent to setting an interval $$$b_l, b_r$$$ to $$$0$$$. Therefore, the interval that solves the problem for $$$a$$$ is the interval in $$$b$$$ with minimal sum (which we subtract from the total sum by deletion). This is a standard problem.
can you please explain equivalence of given operation to setting
b[l:r]to0Notice that the operation on $$$a_l$$$ to $$$a_r$$$ is adding $$$(l-r+1)(l+r) = 2(l+\ldots+r)$$$ (this equality is the key step!) and subtracting $$$a_l+\ldots+a_r$$$. Therefore we can rewrite it as subtracting $$$\sum_l^r (a_k - 2k)$$$ from the total sum of $$$a_k - 2k = b_k$$$.
whoa thanks, I can see it now!!
this idea is so cool.
thanks for sharing your genius approach
dif(l, r): change in sum of the array after applying the operation in l, r.
let's say we have dif(l, r — 1) calculated for all l and we want to calculate dif(l, r)
dif(l, r) = dif(l, r — 1) + (r — l) + (l + r — a[r])
= dif(l, r — 1) + 2*r — a[r]
(r — l): every value in the previous interval increases by 1
(l + r — a[r]): current change
so, if we choose to add some element in the operation, the change in difference doesnt depend on the previous values
thus, the answer is gonna be the sum of the original array + largest subarray sum of b where b[i] = 2*i — a[i]
wow !! very cool.
how did you think of this solution, trying to get intuition so that I can also think like this !!!
i guess i just got lucky. i spent basically the entire contest trying to solve it using some sort of sliding window
ok, that is cool. thanks for sharing your idea.
xyz
your audacity is crazy
I guess the codeforces servers still loves me..
Please check my approach to B. https://mirror.codeforces.com/contest/2169/submission/348983371 Some edge case i miss or whole approach is wrong!!
your aprroach is correct, but there is a case, with * that you're missing
I was thinking but I could not decode.
didnt read completely but try these cases
ohkaay thank u so much I will try this!
try these ; these were the ones i had issues with
Basically, in your approach the infinite pattern checking is correct, but when it comes to finding the maximum, you missed one edge case.
In your code, you counted only <<<<< and >>>>> type of patterns, but it can also be like this: <<<<****<<<< and >>>>***>>>. You missed that * can also come in between.
If you implement this correctly, your code will handle all cases.
Thanku so much I will understand and do the upsolving.
I think codeforces should add an option to report cheaters in a contest.
D1 had a feeling similar to josephus problem .. so made some weird recursion kind of solution but couldn't optimize for D2 .. guess some observation (like different approach for smaller and larger
y?? ) and then math stuff ??just binary search worked for me
ok like binary search the answer
Aand then in validity check .. try to check how many numbers smaller thanAwere crossed out ... something along that line ??keep subtracting A / y for x times. see if the remaining is larger than k.
for D2 ??
D1. I got TLE on D2. still no clue
yeah I did something weird for D1 .. no idea of D2
The key idea is that one operation transforms a position p into
p + ((p-1)/(Y-1)).
However, the added value d = (p-1)/(Y-1) stays constant while p remains in a specific range. Instead of considering it one at a time , we consider jumping(adding) multiple such d . This jump length is (R − p)/d + 1 (we can prove it) , where R =(d+1)(Y−1).
We subtract whole blocks from X and increase p , it can be seen that no more than 50-55 such jumps we need
oh wow !! how come you are specialist
he isnt
what do you mean .. alt account ?
btw I am just saying that I didn't get an idea as someone rated
expertso I was just kind of appreciating the idea .how do you get to this point , have you seen such kind of jumping before ?
we can always think of it repeating a constant task one by one is always bad than doing it in bulk at a time !!
Can you elaborate on why we need only 50-55 jumps (i.e. log 1e12)?
can say (Y-1 >=2)
This is nice . How u come to this conclusion ?
i mean experience or just trying out in live contest[love to hear].
what do you want me to answer ?? I don't get your question
ok ok , calm down. It is not so difficult to come up with the idea :) .
Suppose we have a position $$$p$$$. If $$$p \bmod y \neq 0$$$, then it changes as:
The non trivial idea is as follows: We start from a position $$$k$$$, and we want to find the original position $$$p$$$ that was transformed into $$$k$$$.
Let $$$k = q \cdot y + r$$$ (where $$$0 \leq r \lt y$$$). If $$$q + r \lt y$$$, then we can simply perform:
This operation directly moves $$$k$$$ to the end of the current interval. If this process stays within bounds (does not spill over the interval), you can repeat it as long as the condition holds.
Once $$$q + r \geq y$$$, we want to find $$$q_2$$$ such that:
which rearranges to:
Here, $$$r_2 \leq y - 1$$$. To check if $$$r_2 = y - 1$$$, simply verify:
now , solve for $$$q_2$$$ and update $$$k$$$:
By applying these steps, you obtain an algorithm that works in $$$\sqrt{x}$$$ steps.
ok, thanks.. I will try to understand more and upsolve later
I tried this exact approach once i noticed the quocient was repeating, but still got TLE on 25. do you have any idea why? I couldn't see any edge case.
I mean it was quite of a reach, overall solution should work on $$$\mathcal{O}(T\log(10^{12})$$$$$$\sqrt x$$$), which is around $$$10\cdot40\cdot10^6 = 4\cdot10^8$$$. Did yours get AC?
https://mirror.codeforces.com/contest/2169/submission/348965036
why are you doing binary search ? If you read what I do ,there is no binary search involved.
The idea was the same "We start from a position $$$k$$$, and we want to find the original position $$$p$$$ that was transformed into $$$k$$$.", i tried to solve this using BS, then my check was supposed to find the final position for a given number $$$p$$$. Now I'm not so sure I understood your solution, it is really similar to what I've done in my check function. Would you care to explain a little further how is it that your steps end up finding $$$p$$$?
you simply start with $$$k$$$ , and find what next position $$$p$$$ satisfies $$$p \mod y \neq 0$$$ and transitions to this $$$k$$$ , and then update the $$$k$$$. You can look at my submission.
xyz
yeah same ! I did D1 but not D2 .. will try to upsolve later
How to d2? I solved d1 by binary searching over if there exists an element $$$ c $$$ such that at least $$$ k $$$ elements survive $$$ \lt = c $$$ after all operations.
My $$$E$$$ solution:
First, $$$ans=sumc-minc$$$.
Considering only the point $$$i$$$ in the lower left corner and the point $$$j$$$ in the upper right corner, the answer is $$$max(sumc + (x[j] + y[j] - c[j]) + (-x[i] - y[i] - c[i]))$$$. Note that absolute values are not required here, as some "erroneous values" will not exceed the actual maximum (the same logic applies as in https://mirror.codeforces.com/contest/1859/problem/E).
Therefore, we only need to preprocess $$$mx1 = max(x[i] + y[i] - c[i])$$$ and $$$mx2 = max(-x[i] - y[i] - c[i])$$$, then update the answer with $$$sumc + mx1 + mx2$$$.
It is also possible that the lower left and upper right corners are not determined by a single point but by two points together. We only need to similarly record $$$mx3=max(x[i]-c[i]), mx4=max(y[i]-c[i]), \ldots$$$ and update the answer.
It is also possible that the rectangle is determined by the top-left and top-right corners. We don't need to do more caseworks; simply multiply all $$$x$$$-coordinates by $$$-1$$$ and run the solve function again.
AC code: 348984311
Pls put it under spoiler because it spoils the problem for ppl just wanting to read general comments here
348953962
Why does my code get a TL?
I am jumping over the steps like in this problem
CSES problem
There is a problem that is similar to the D2 solution. https://mirror.codeforces.com/gym/105588/problem/C
D2 is too mysterious.
348953962
Why does my code get a TL? I am jumping over the steps like in this problem
CSES problem
d1 is similar to 1852A - Ntarsis' Set
I knew I've seen this problem before.
Sol D?
My code for C passed but i don't have proof
oh wow!!! ... you did some 2 pointer kind of thing . interesting !!
Yes, and I don't know why.
hehe !! congrats I guess :P
i tried to do it using two pointers but i did it wrongly how could i see your solotion ?
https://mirror.codeforces.com/contest/2169/submission/348933719
thank you !
this contest b ; i had the proper idea in 10 mins after start but forgot the cases in which the counter resets but has * as past state and was frothing at the screen like a code monkey wondering what went wrong and just managed to find that 1 min after contest ended ; hopefully i learn something for the future ;
348953962
Why does my code get a TL? I am jumping over the steps like in this problem
CSES
Problem D seems awfully similar in concept to https://mirror.codeforces.com/contest/1852/problem/A , the binary search / two pointer in the question linked is changed here to math due to being multiples of a single integer but doesn't change the solution significantly. Just wanted to make the authors aware about it.
It's similar to D1, but not D2.
people are hating it (especially D2 just because they couldn't solve it).
The problem itself yes but if you open the editorial you can see the linked problem was originally intended with number of ops upto 10^9 and the solution posted is also for that which matches D2.
D1 seems to be simpler than C
RP++ :))))
Here is my live Screencast with detailed explanation for [A-C]. Video link : YT Video (It's in Hindi Language).
I may upload explanations for D2 and E if anybody wants.
yes please D2 and E will be helpful
Just Watched your solutions for A (visualization approach) & B, aswell, pretty nice, Thanks !
I just overcomplicated A For some reason, visualizing helps to solve quick for sure !
i solved 4 qns only
One of the first div2 constest from a long time where B was actually easy and wasn't harder than C i think
Hi There , i just do stupid thing for fun , i saved answers for d2 for test 27 , 28 i can hack it inf times by this way i hope u consider this awoo
good round, thanks
I unnecessarily did a trash ahh dp in C
First I did a $$$O(n^2)$$$ dp then optimised it to $$$O(n)$$$ For $$$O(n^2)$$$ I did a naive dp with
dp[i][done]telling if we havedonethe range operation or not tilli. So transitions are justThis a very naive dp. To optimise the top term we can see that we can use prefix sum. So we just store the
And to optimise the bottom term we can multiply the
and get the common j terms out. So
So
So now
dptransition will be likeand
and this is
:yayy:
Solution link: https://mirror.codeforces.com/contest/2169/submission/348964665
Meanwhile me using segment tree.
shit? nah man, this is goated. I also wrote DP, tho I think mine is easier to comprehend(no offense, man)
https://mirror.codeforces.com/contest/2169/submission/348989596
The Hack of problem A is the most serious attack in ex-ICPC rule because the score of every problem is equal, but most people gain the smallest penalty in A. Never make weak tests in A please.
nuh uh, where is the editorial?
another mathforces
qp
qp
I participated in Educational Codeforces Round 184 (Rated for Div. 2) and managed to solve 3 problems. Huge thanks to awoo , adedalic , BledDest , Neon , Roms and FelixArg for preparing this contest — I really appreciate the time and effort you all put into it!
Programming is just a hobby for me, but contests like this always motivate me to improve and learn more. Looking forward to doing even better next time!I participated in Educational Codeforces Round 184 (Rated for Div. 2) and managed to solve 3 problems.
Huge thanks to awoo, adedalic, BledDest, Neon, Roms and FelixArg for preparing this contest — really appreciate the time and effort!
If programming is just a hobby for you, then why do you use AI in contests? Your all submissions are AI-generated....
Bro you could just try to delete AI comment's And you didn't even do that
Your comments sound a lot like those of artificial intelligence.
dig.
You can see that problem D2 is highly similar to problem C from ICPC 2024 EC Kunming, and I think this is unfair. https://qoj.ac/contest/1871/problem/9864
Okay fine... I might be stupid for missing the "=" edge case in A in my solution and I deserve to be hacked, but I'll excuse myself as I only had 3 minutes total to get the problem accepted so not much time thinking... But how'd the problem creator miss it?! :S
can someone tell me which test case my solution get hacked ? for problem A
348924910
Is there a system testing for this contest?
Why F using 5*log times NTT lead to TLE?Is my NTT too slow or just having another method?
me too
From the editorial it looks like it's not the intended solution. I tried this during the contest and it got hacked, but I managed to get it to pass by adding some pragmas: https://mirror.codeforces.com/contest/2169/submission/349157794
Isnt the hacking part over? When will the ratings come? Or because of the some people had problems in the beginning the contest turned into unrated?
Has this contest become unrated , i dont know why i didnt get rating update****
Add DP to problem C, as can be shown here:
https://mirror.codeforces.com/contest/2169/submission/348989596
I love this game!
1
rating is not updated any idea when it updated
why unrated?
Just update the ratings man, i did 3 questions and i was so happy that I’d finally become pupil and now this because of a few people?? If they had a issue they could’ve simply skipped the contest, why should the round be unrated because of a issue like this?and no official response either
Your first code is hackable, I hope you are aware of that. You will become a pupil in this round, so do not worry.btw congratulations in advance.
How is my code hackable? Also apparently we’re from same college lmao
You should have totally ignored elements equal to A (don't count them at all); and then it would have been a correct solution.
This statement was in bold for a reason, "in case of a tie, Alice gets the point".
Or else, even A can be the answer if you are considering elements equal to A and you should've handled the condition.
ooh thanks, got it
It's an educational round with a 12-hour hacking phase. So it's normal for it to take 16 to 24 hours to announce the final rating. Keep patience; it will be announced soon.
When will the change in rating be reflected?
Let the system test end first !! You may expect rating change in at most 2-3 hours. Till that time, enjoy ABC 432.
I want to know,too.But the screen show me that "system testing" and "95%" now . I don't know why...
TUTORIAL PLZ
I think user testerAbstract cheated
He use if (!(cin >> t)) is one of chatGPT's coding style
i agree with you not only that he used different typenames throughout the contest, sometimes he will use long long, sometile using ll = long long, sometimes i64=long long, and then using unit_32t instead of long long for quetion F which is like okay for ntt but not particularly needed but chatgpt still uses it, moreover he sometime uses t and T for testcases sometimes with if(!(cin >> t)) sometimes without, and i refuse to believe he wrote entire templates for each code and got this, there is literally no consistency in his perf and coding style alike. he is a cheater
Agree. He has even got rank 1 and reach 2100+... There's no meaning to refer cf rating anymore.
are there some editorials for this ?
how to know what input hacker used for our code?
It was something like this:
1
4 2
1 2 2 2
i think he is asking in general
yes , so anyone can see it :,)
i think that will be available after the contest ends (after system testing is finished)
oh so you find it yourself , yes i think i should go for value comparision instead of position
why System testing is taking so much time ?
Is it normal for system testing to be stuck at a specific percentage for longer than average? Just curious :3
1h ago: System testing (95%)
now: System testing (95%)
My D2 submission: In queue
Cannot see my contest submissions in Contest -> My Submission page, only non-contest ones are visible
You mean people who did not participate in the contest and are now making submissions are having higher priority in queue than the ones who did participate in the contest? :(
this is standard, my guess is that many bots are spamming submissions which is causing a delay in sys tests
I feel like the system is flawed here, first they should prioritize contestant submissions and get the results published and then deal with submissions that are made by folks who did not participate
you feel like that rn, but there is nothing you can do to change your contests submissions, people practicing need priority because they are currently working on the problems, system testing does eventually finish so no change whether it happens right away or 2 days later. usually they dont take this long really unfortunate, but the system is correct.
I don't know the details, but the progress of system testing seems get stucked for ~1h, and my D2 hasn't been judged till now. Hopefully things will get right soon.
Yeah i'm hoping to reach pupil with this contest, though I'm not quite sure whether my solution to C will pass the tests or not.
i see, it becomes slower than before, after it reachs 90%
By the way, I realllllllllllllllly like your profile picture, i love clannad, i like nagisa!!!!
Me too! I chose the most impressive one to be my profile.
You recommend watching clannad ?
BTW Chalotte is also a good anime!
Is this contest delay?
System testing rn :
Yoo What's up bro. :)
Why's it stuck on 95%?
stuck is like my mind and code
why it's taking so much time in system testing ?
when will the ratings be published?....for 6 hours its showing 95% system testing
Why's is system testing stuck on 95% from last few hours :(
This has to be one of the worst contests bro...
system test at 5 hrs before — 95 % system test now — 95% system test 1 light year later — 95%
We are getting TL on system test :(
Now at 99
Was this match unrated?
Nyan't
If someone registers for a contest but doesn’t actually participate, does their rating stay the same? My friend forgot to join this contest, and his rating didn’t change. Or maybe that only applies to Educational contests?
Yes, rating stays the same. Rating changes(if applicable) only if a contestant submits a solution in the contest.
Vote up if the problems were nice!
.
Hello Codeforces Team,
My handle is rakshithnayakam08, and I recently participated in Contest 2169 (Educational Codeforces Round 184). My participation was marked as skipped, but I would like to request a review because I believe I met the contest rules and did not use any unfair means. Here’s what happened and why I believe the “skipped” status is incorrect: I actively solved problems during the contest, specifically I attempted problems A,B,C. I coded the solutions myself without any external help or collaboration. My logic and code style are consistent with my previous submissions. If needed, I am willing to provide a detailed explanation of how I arrived at my solutions: my thinking process, test cases I used, how I debugged my code during the contest, etc. I followed the contest conditions: no outside assistance, no AI-help, no code sharing, and I submitted within time. If there are any particular concerns or similarities flagged by the system, I respectfully believe they can be explained by coincidence or by common patterns rather than misconduct. I respectfully request you to review my submission history and, if possible, restore my contest participation and rating/standing for Contest 2169. Thank you very much for your time and understanding.
Hello Codeforces Team,
My handle is rakshithnayakam08, and I recently participated in Contest 2169 (Educational Codeforces Round 184). My participation was marked as skipped, but I would like to request a review because I believe I met the contest rules and did not use any unfair means. Here’s what happened and why I believe the “skipped” status is incorrect: I actively solved problems during the contest, specifically I attempted problems A,B,C. I coded the solutions myself without any external help or collaboration. My logic and code style are consistent with my previous submissions. If needed, I am willing to provide a detailed explanation of how I arrived at my solutions: my thinking process, test cases I used, how I debugged my code during the contest, etc. I followed the contest conditions: no outside assistance, no AI-help, no code sharing, and I submitted within time. If there are any particular concerns or similarities flagged by the system, I respectfully believe they can be explained by coincidence or by common patterns rather than misconduct. I respectfully request you to review my submission history and, if possible, restore my contest participation and rating/standing for Contest 2169. Thank you very much for your time and understanding.
Hello, I received a similarity warning for my solution in this round. I did not share my code with anyone or copy from anyone. It is possible that I once used an online IDE that unintentionally made my code public. I understand this is against the rules even if unintentional, and I sincerely apologize. I will make sure this never happens again. Thank you for checking.
Hello. I received a system message saying that my submission for problem 2169B (submission ID 348926906) significantly coincides with another user’s solution. I want to clarify that I solved the problem independently. My approach: I modelled the string as a directed graph, where each index has edges depending on <, >, or — (or other characters meaning both directions). Moving outside the string is treated as reaching a special boundary node. 1. I first detect cycles using an iterative DFS to ensure that no infinite loop exists. 2. If a cycle is found, the answer is -1. 3. Otherwise, I compute the maximum length path to the boundary using DFS + memoization. 4. The final result is the maximum of these lengths. This approach is a natural and common model for this problem since it essentially reduces to: build transitions, detect cycles, compute longest path in a DAG.
Implementation details proving independence: I used a sentinel node sh = n to represent out-of-bounds transitions. I implemented DFS iteratively (vector<pair<int, int>> stk) instead of recursion to avoid stack overflow. For DP, I used an explicit stack with (node, expanded) pairs to simulate post-order traversal. I used INT_MIN/4 as a “NEG” value in the DP memo array to avoid overflow. These patterns reflect my usual coding style and appear in my editor’s local history.
Why similarity may appear: The structure of the problem strongly guides solvers toward the same transitions + cycle detection + DP solution. Many correct solutions may therefore look similar in logic and structure even if independently written.
I can provide evidence if required:local file timestamps, IDE local history showing how I wrote the code, git logs (if needed), screenshots of my environment at submission time.
I did not share my code with anyone, nor used any public code-sharing service. Please let me know if you require further proof. I am willing to cooperate fully. Thank you.
—aashiumrao