Hello Cowodeforces :D
Proof_by_QED, Lilypad and I are very 
to invite you to participate in Codeforces Round 993 (Div. 4), which will start on 15.12.2024 17:35 (Московское время). There will be $$$8$$$ problems, with one split into two subtasks, to be solved in $$$2$$$ hours and $$$15$$$ minutes. Participate or you'll have to wait another millennium for a Div. 4 round.
The format of the event will be identical to Div. 3 rounds:
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behavior. To qualify as a trusted participant of the fourth 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 point of 1400 or higher in the rating.
Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), you may choose to participate rated or unrated.
We want to express overwhelming gratitude to the following orzosities for making the contest possible:
Vladosiya for reviewing the contest.
(VIP+) chromate00 for the idea for one of the problems.
Our testuwuers: awesomeguy856, (VIP) Dominater069, Error_Yuan, Edeeva, -firefly-, (VIP) Friedrich, 18o3, Intellegent, amoeba4, Starlight-Sailor, efishel, yoru_sacri, larush, (VIP+) chromate00, DivinePunishment, kevlu8, reirugan, mathtsai, RobinFromTheHood, Filikec, macaquedev, pianapolataa, and members of my high school's coding club including but not limited to IceWolf898, MC3297, and ETL.
(MVP++) MikeMirzayanov for Codeforces and Polygon.
guys i think we got a bit carried away while writing this contest
Always the good round from the goat!!!
Will there be an interactive problem ?
u are silly
As a tester, I can confirm that one of the problems was based on Honkai: Star Rail.
WOW zrnstnsr tested round
tester leaking contest exposed 2024 caught on camera
Which?I can't find that!
It's C problem.
8 problems in 2.25 hours? time to :cope:
It feels weird reading time like that.
As a participant, I hope there are no problems based on Honkai: Star Rail.
How can I become a testuwuer?
You can message me to be considered, but I usually only accept / reply to people that seem active, promising, and honest on a variety of factors.
I think I know what is drawn on that picture. It's Gekko's moshpit on budget.
But I think you need to shut the fck up and stop cheating
As a tester, I just want to vouch that Intellegent is very intelligent
As a tester, I don’t know how he came to this conclusion.
As a tester, I can confirm that there will be eight problems, with one split into two subtasks, to be solved in 2 hours and 15 minutes.
Additionally, I can confirm that each problem will require you to write up to zero or more lines of code.
Thank you so much for the valuable information! It will be incredibly helpful not only for this contest but for all my future contests as well.
As a tester, I was tested.
PS Welcome to CP, Shrek Jr :)
As a tester, I don't know what kinda brainrot I just created with the artwork
As a tester, the art for this contest is beautiful
probably my last contest on cf .hoping for good perf :)
I analyzed your account.
Looks like you can reach expert levels in 5 months with good practice.
Don't leave CP :(
As a tester, ChatGPT solves n problems in this contest where n is an integer such that 0<=n<=10
As a tester, a few problems of this round took me to nirvana. Hope you enjoy too!
As a tester, i have no clue how i got VIP without doing anything
You ate 5 STAR maybe...
is that a lobotomy corporation reference
Project moon sleeper agent activated
GEOMETRY DASH MENTIONED!!!!11 FIRE IN THE HOLE!
FIRE IN THE HOLE
After becoming a specialist, this is my first unrated contest in Div. 4. I think it will be fun!
we got an orange-ranked lobotomy patient before gta6 thats crazy
is auhthority from this contest from russia? cuz im taking notes of words btw!
what is point of div4 when ChatGPT exists at this point?
I know, I know rule exists however you know
I don't know why we still have this kind of comment every time. It's about general perception: if we all agree that we must not use AIs during contests, then we just simply need to ignore those who use AIs and don't give credits to them. It's up to the admins how much they can actually catch the cheaters, and there's not much we can do about it. We do contests for our own good, not to perform better than AIs.
to let those who don't use gpt improve.
As a tester, the problems are very skibidi
cute anime girl testing problems?!
Wow. Another cry round! <3
As a participant I will be giving the contest from this account only.
Another div 4 where thousands of indians and bangladeshi will be caught cheating
cool
To every Newbie/Pupil trying to up improve. I wish them All the best.
Bro got caught red-handed in ratism.
can anybody tell me where i can practice window function questions in sql ?
not the right place to ask
try sql 50 from leetcode, they cover a lot of good ques and concepts.
https://leetcode.com/studyplan/top-sql-50/
As a tester, I believe this will be the best Div4 ever! Enjoy it!
60th comment ;D
69th comment :)
As a, I can say this.
Umm, you forgot to mention and orz MikeMirzayanov
Wait, how is this emoji or sticker work? I mean how can I use them
How can I become a legendary Grandmaster?
Solve all div.4 problems in the first minute
what's the deal with vip and vip+ testers?
hehe
your joke is making the rounds again tickbird
I think they're very "Aoouhhhh!" to invite us
Just became green for a week, hope don't gray back this time :)
Can you make div 2 next time
hope you all get greens and give your 100% with best wishes
Barely eligible (flex) :)
what will be the points distribution ? anyone ?
As a participant, I hope I can solve the problem based on Honkai Star Rail.
May the journey lead us skyward.
Congrats you solved the problem based on Honkai: Star Rail
doesn't this kinda defeat the purpose of div 4 contests since most participants are newcomers,and don't really have a lot of experience with contests.
is this why my contest got converted to unrated?
we haven't given ratings yet ig cuz no one graphs is showing the div4 rating
ah yes , it just got updated, i was sulking af till now
same lmfao
I need 200 points to reach cyan,I hope i can do it today.
I'm new and haven't participated in any rated rounds. Can I still participate?
thanks.
yes
Beautiful art by chromate00!
Knee surgery tomorrow
As an unrated participant, I wish everyone good luck and a positive delta.
...and for myself, contribution++. :)
Codeforces Round 1000-7
Never cry, and keep Smile ing.
Out of my curiosity, does Lilypad come from HIMYM?
To be honest, it doesn't make sense to have $$$VIP$$$ and $$$VIP+$$$ testers. $$$VIP$$$ already has $$$very$$$ in its name, so why don't you call $$$VIP$$$ testers $$$IP$$$ (important person) testers and $$$VIP+$$$ testers $$$VIP$$$ testers? Because I'm sure the $$$VIP$$$ testers weren't integral to the round's success, even if they might've helped out a bit. And contributing a problem arguably sounds like a $$$VIP$$$ thing, but I wouldn't call it a $$$VIP+$$$ thing.
play hypixel
Hoping the problems to be bit easy unlike last div-4 !!
Was hoping that I could solve at least 4 problems but have to settle for 3 problems today :-(
As a GeometryDash 4k stars player , I feel sorry that I miss this round :(
Excellent contest! I really liked 3 of the problems.
(Btw an interesting coincidence, the first problem of this contest is named "Easy Problem", there is another problem on CF of the same name 1096D - Easy Problem, which happens to be the first DP problem I solved in my life.)
The problem names are references to geometry dash difficulties
BIG FAN BHAIYA
Nice Div. 3 round
I've added hints and thought process for G1. Medium Demon Problem (easy version) on CF Step
How to do G2 ?
Make a directed graph $$$i \rightarrow a_i$$$ and another inverted graph $$$a_i \rightarrow i$$$.
For G1 : Answer is the length of the longest chain which falls from a cycle + 2. Can be calculated by a multisource BFS on the inverted graph. For G2 : Answer is the largest subtree size of a node not belonging to any cycle + 2.
That was a real mathforces
Anyone has a neater solution for D ? I solved it using simulation because it is known that a solution exists but I would appreciate a neater solution.
You can simply make every number appearing once in the array, then all of them will be mode.
Understood.
Just looked at your performance in the contest. You performed so well. Congratulations !
yes just output the distinct element in their first appearance and continue with the normal output in the rest 12345 so on
1 1 2 2 1 6 3 3 1 4
1 5 2 7 8 6 3 9 10 4
output 1 at 1 2 at 2 6 at 6 3 at 3 4 at 4 rest out the normal remaining out of n
note that the max value of an array element is n, so keep track of the numbers from 1 to n which dont appear in the given array. now, traverse the given array from left to right, if an element occurs for the first time, add that to the answer array, else you add a number that does not occur. Now every element from 1 to n will appear only once, hence the mode criteria is satisfied
For G1 I thought the process to remove the cycles and count the longest chain , such a shame couldn't Implement it in O(n)
the moment i pressed submit F contest over :(
Problem F was cool; loved it!
How did so many people solve E? I couldn't come up with even a logic that works.
Iterating through all $$$n$$$ and calculate $$$k^n$$$. Notice that you only need to iterate till $$$k^n \leq 10^9$$$, and since $$$k \geq 2$$$, it will be at most $$$30$$$ possible $$$n$$$. Then find the bound of $$$x$$$ for each $$$k^n$$$. 296642769
My best performance so far, hope to finally reach specialist (still don't know where my G2 went wrong sadly... could've been better).
There's no constraint on either $$$n\cdot m$$$ or sum of $$$n\cdot m$$$.
Nopes , my soln is not varying on O(n*m) still it's getting Tle on testcase 25.
Testcase 25 hacks almost all $$$O\left(q(\sqrt{n}+d(n)\log{n})\right)$$$ solutions. It's added on open hack phase.
One of the accepted submission of a friend of mine, when I submitted it through my id , it's now giving tle on test-25, how can this be possible
Check out my submission
Initially got tle on test 25 ,after changing long long back to int, it runs just within the constraints.
296802950
Why can't I see anybody's submissions in/out of contest except mine? It says N/A. Please help me out.
Nice problems F, G1, G2 !
why my submission 296750050 gives tle, i am not able to handle overflow may be.
Try Binary Search to find the first element within the range in stead of Brute forcing two nested loops.
296676561
296729877 I wrote this program for harder problem and i understand that it has time complexity issues but i have no idea how to make the code more time efficient with the approach I used, would greatly appreciate any help
You had the right idea to realize that by simply permuting the order of numbers 1 through N to prioritize the numbers that showed up first. This would result in an array where all of these numbers would be considered as a mode
(count == 1).I believe the really slow part of the code is the nested for-loop you have for appending the numbers that don't show up because it would run an O(n) search for every number 1 through N, for every index until it fills the array. To fix this, you could have a
lastSeenvariable to track the lastithat you appended to the array, so that instead of looping from 1 through N, you would cut it short to i through N.To make it cleaner, you could use
setsinstead. Create a set (straight from the input) of all numbers that show up in the original array. Useset_differenceor similar method to obtain all the numbers that didn't show up. Then, combine these two by appending the second to the first while maintaining the order of the set. That way, you don't have to spend O(n) every time you test for whether a number has already appeared.Hope this helps! :)
P.S. Here's my submission and implementation of the above. It's a bit messy though since I'm a noob :P 296684484
when ratings would be given for this contest???????????
Edu-style rounds (including Div 3 & 4) will go like this:
When ratings are updated, the "RATING CHANGES" link is added to the contest standings page. If there's no such link, the ratings are not updated yet. Just wait until the ratings are updated.
I have a doubt will this contest will be rated for me or not ? I have a contest rating of 750 ..? The contest is completed but my rating is not updated why ?
Because System Testing is going on.
First blog in which there was not a thanks to MikeMirzayanov
would the newcomer have rating???
Newcomers and those who have <1400 rating will be rated. Just wait.
Could anyone help me with my code? https://codeforces.me/contest/2044/submission/296745472 Codeforces said it has runtime error on test case #10 . But when I try the code and the test case #10 on my pc, also on ideone ( https://ideone.com/eVDhX0 ), I found no error. Is there a fix for my code? I just can't find the error.
fire in the hole
At first, I apologize for registering an alt. But it's an necessity because my account transparent_heart was banned while participating in the Div. 4 contest.
And I can't send message to cry.
Hi cry, I participated in the Div. 4 contest yesterday. The problems were awesome and I really enjoyed the contest. What's more exciting was that I was on the first page of the standing! I really appreciate you and other authors as well as the coordinator for preparing such an fantastic contest!
However, everything changed at the time I submitted my solution of problem F. I'm really shocked that I was banned! I don't know why. I should have been reached my best performance but now my account is disabled!
All the idea is from my mind and the code was written by myself. You can see my submissions to prove it.
Do you know the reason why I'm banned? I just want an explanation because that account is very important to me. I VPed 30+ contests using it!
I may be a little radical. Please forgive me. But I'm really frustrated and confused. Sorry :(
The most difficult thing now is to get the admin to see my comments lol
Hi Vladosiya, sorry for disturbing but can I have a few minutes of your time to get a reason?
yay I'm back XD
I have entered rated in the contest but still my rating in contest is showing N/A can any editor have look on the issue?
Hey @cry , @vgoofficial, @Lilypad Question D my python code runs in O(N) however it gets a TLE after hacking while the same code in C++ got accepted Is there anything I can do about this ?
~~~~~~~~~~~~~~~~~~
tests = int(input()) for _ in range(tests): n = input() arr = list(map(int, input().split())) # print(arr) # future = set(arr) ans = [] nums = set()
for item in arr: if item not in nums: nums.add(item) print(item,end=' ') for i in (set(range(1, len(arr) + 1))-nums): print(i,end=' ')print()
if item not in nums:This actually runs in $$$\mathcal{O}(n)$$$ now your code runs in $$$\mathcal{O}(n^2)$$$ which is not good , do it like me , maintain an array $$$done$$$ and check for each index normally , instead of searching.
Nums is a set tho and searching in a set is O(N), also I retyped the exact same code in c++ and it got accepted
because searching an element on set on C++ is $$$\mathcal{O}(\log(n))$$$ which is fine constant factor ($$$\approx 20$$$) , but in Python it's $$$\mathcal{O}(n)$$$ is too much making it quadratic.
so $$$\mathcal{O}(n\log(n)) \approx \mathcal{O}(20n)$$$ is much better than $$$\mathcal{O}(n^2)$$$
$$$n=|s|$$$
A set is a hasmap right ? Hashmaps have o(1) lookup time https://stackoverflow.com/questions/7351459/time-complexity-of-python-set-operations
O(1) lookup time, in some situations, but also it can be O(n) in others. handmade tests can be made so that the O(n) situation occurs, and for your code to be O(n^2)
you got hash hacked, refer to this. For this problem i would recommend to use a boolean array tho.
How is it possibile that I got accepted during the contest on problem F and now it gives me TLE on test25. I wrote the solution with the maps and also in the editorial it is a optimal solution for this problem.
Using unordered_map instead of map change the result to accepted. If during the contest it would have given me TLE I would have changed it and got accepted. It doesn't seem fair.
https://codeforces.me/blog/entry/137306#comment-1228128 Check this out.
The open hack phase is an official phase that was announced prior to the contest. Many submissions get hacked during this phase and many others fail on system test on these tests. It's not unfair.
296865335 296893248 The two are very similar codes and I feel they are actually the same but the give a very diff runtime with the first working in 2s and the second in 4s , what might be causing that ?
Guys, its me.
too late :weary:
WATER ON THE HILL!!!!!!!!
I'd like to ask a question. If my submission is found to be plagiarized through the plagiarism check, will it be counted as zero solved questions for scoring, or will the results of this competition be directly removed? After my submission was found to have plagiarism issues, more than 100 points were directly deducted from me. Is this a normal phenomenon?