We invite you to participate in CodeChef’s January Lunchtime on 30th January from 9:00 PM to 12:00 AM IST. Note the unusual time.
There will be 3 divisions, each division containing 6 problems!
This Lunchtime, ByteDance is joining CodeChef as the official contest recruiter! The tech giants, who have their presence globally established through a range of content platforms, are looking to hire for multiple positions for their Singapore office, including — Algorithm Engineers, Backend Engineers, Data Engineers, Data Scientist, Machine Learning Engineers, Research Scientists, Frontend Engineers, Quality Assurance Engineer, Research Engineers, Software Engineer, and Site Reliability Engineers.
Joining us on the problem setting panel are:
Tester: Rahul amnesiac_dusk Dugar
Setters: Jatin jtnydv25 Yadav, Ashish Ashishgup Gupta, Smit l_returns Mandavia, Akash Whiplash99 Bhalotia, Hriday the_hyp0cr1t3 G, Shubham TheOneYouWant Anand Jain, Daanish 7dan Mahajan, Utkarsh Utkarsh.25dec Gupta
Statement Verifier: Jakub Xellos Safin
Editorialist: Ishmeet Psychik Singh Saggu
Video Editorialists: Chirayu Chirayu Jain, Prachi agarwal19 Agarwal, Darshan darshancool25 Lokhande, Yashodhan ay21 Agnihotri, Bharat Singla, Shivam Bohra, Aryan Agarwala, Radoslav radoslav11 Dimitrov, Meet myth_gemphir Singh Gambhir
Mandarin Translator: Gedi gediiiiiii Zheng
Vietnamese Translator: Team VNOI
Russian Translator: Fedor Mediocrity Korobeinikov
Bengali Translator: Mohammad solaimanope Solaiman
Hindi Translator: Akash devils_code Srivastava
Problem Submission: If you have original problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.
Prizes: The following will receive CodeChef laddus, with which the winners can claim cool CodeChef goodies. Know more here:
- Top 10 Indian and Global Users (Overall)
- Top 10 Indian and Global School Students
The video editorials of the problems will be available on our YouTube Channel as soon as the contest ends. Subscribe to get notifications about our new editorials.
Admin Note:
This Lunchtime is a replay of Codeflows, so most problems do not have subtasks. We have added some easier problems for Div3 and Div2 problemsets, and the contest is delayed from its usual time to avoid clash with the final round!
Good luck and have fun!
Update:
Congratulation to the Codeflows onsite winners:
- Petr (900/900 points — only one to solve all problems)
- kabuszki (810/900 points)
- bicsi (800/900 points)
Update 2:
The January Lunchtime is being made unrated due to the various issues that users faced.
With the high traffic that we have been getting recently, we have been facing issues with our infrastructure, and the contest experience has been bad. Keeping this in mind, we are postponing all rated short contests, till a time when we are sure that the contests can be held smoothly, and we've had a smooth testing round. In particular, the Starters contest scheduled for 31st January is being postponed indefinitely, till further announcements. Apologies for the inconvenience.
Note: The February Long Challenge will take place as usual.
Not all participants but only school students because it's a LT, or this time is an exception?
It will be given to both as an exception :D
Can we expect another server issues?
Because It was very irritating that happened last time
Hopefully it's better this time, CodeChef now has more servers to handle the traffic.
The story of every Codechef contest : click
Last CookOff worked smoothly for the last 2 hours, hopefully this LTIME issue is resolved soon as well. I'm sorry, I can't really help with the server related issues :(
Well I don't know about the actual statistics of how many people started the contest versus how many people were still doing it in the last 2 hours. But it definitely wasn't the full audience that started the contest. So the claim that the server worked fine for the last 2 hours is telling the half truth.
Also, I do understand that you cannot do anything about it except ask the Codechef team to fix their issues.
On top of that, they make last contest rated despite knowing the fact that many of the participants leave the contest midway due to server issues
Please take some time to resolve this issue..This is really frustrating : (
No subtasks :(
Some problems will have subtasks, but yes, most of them do not have it.
Thank you Ashishgup!
For some reason, my rating only goes up in most of your contests. I REALLY hope that trend continues as I was destroyed in last 2 contests here.
Good luck :D
Please try to keep the usual timings for future lunchtime contests.
Why unusual time?
As mentioned in the blog, it was to avoid the clash with Codeflows Finals which ended at 8:30PM IST.
What does "replay of Codeflows" means? The problems will be same as Codeflows?
Some problems are shared, some are exclusive to LTIME — but yes, most of the harder problems are same as Codeflows.
This line is definitely not for Indians as they recently fired hundreds of Indian employees aside from that Thank you for the quality and quantity of problems :)
I think server are down again .Problems are not loading
Here we Go again
I can't submit lol
Long Queue again :(
Cannot submit due to error . Waiting from 4 minutes.
server started crashing wow!!
Codechef, raise funds like codeforces. We will be happy to donate, but please improve your servers. My solution is running for the last 15 minutes.
I'm not even able to submit : (
Such a time waste to participate in Codechef Contests nowadays.
bruh
Leave Codechef!!!
Maybe this happens because the easy problems are way too easy and a lot of people submit
:(
Its common for codechef these days to hold contest just to disappoint people
ok
ok
ok
Bro how many server codechef have ?
same as number of living dinosaur in 20th century
Another one bites the dust.
sigh this is really the fourth time in a row :|
You are allowed to make 1 submissions in 25 seconds on CodeChef..
Waiting from past 15 minutes to submit.Are these servers hosted on heroku app?
.
The contest is ongoing, whether the codechef servers are crap or not, i don't think you should be posting your questions here which could compromise the integrity of the contest.
I apologize, I simply didn't knew where to ask it. I didn't feel like a question like this could reveal anything. But if it's anyway a problem I will try to remove it.
Ask the questions of the running contest in the comment section below the problem, if it is a valid query than the setters will definitely answer.
At the bottom of the problem page there is a section of comments, you can ask there.
When submitting a solution is harder than solving the problem.
my submission is on queue since hour.
I don't think there is any queue issue (2-3 mins atmax?) — can you link your submission?
I don't think so...three solution got accepted in less than an hour.
damn bro u livin in 2031
Nice meme.
"""three solution got accepted in less than an hour."""
Has website stopped loading ? In my case i am not able to load the website itself currently .
It's working
I am trying to submit a solution but as soon as I go to sumit page it is not allowiung me to select the language. Please help Ashishgup
I'll ask the CodeChef team to check
I thought that I spam submit a lot so they remove the laguage selection to not let me submit again LMAO :))
Ashishgup I think problem statement of Shifting Spoons DIV2 wrong https://www.codechef.com/LTIME92B/problems/SHSPOONS .
In Output section it's written $$$p ≠ n$$$ whereas in problem description its written $$$p ≠ q$$$ . So is both constraint correct ?
Please clarify .
It's $$$p \neq q$$$, sorry.
20min queue for problem D
click My submission -> Then click -> view on your queued submission. Hope you can able to see the verdict.
Waiting for judging from 20 mins :(
503 for submit page 4 mins before the end! Really?
I got the page 1 mins before the end, submitted and ... 405 Not Allowed :)
EDIT: adding to that, that for CARPD I still have running for 23 mins ago.
Middle click submit 10 times, it'll open 10 tabs out of which atleast 1 will work. This is what i do
People here complain to Ashishgup as if he is the owner of Codechef :D
Chill please. Guy is doing God's work if you ask me.
Why people always talk about making a round unrated. TO prepare and test a round, honestly lots of effort required. And server issue was same for all. Hence why u guys ask for unrated contest. Pay at least a minimum tribute to the setters. Its really horrible for those who set the problems. But if you loss rating today a bit, u might get it back tomorrow.
If the contests are held like this then I am not sure when will I get it back.
I will be getting positive delta in this contest but then also i think it should be unrated .
The thing is if you don't make unrated these contests and suppose codechef like every year holds icpc and does the same shit then what will happen ?
Please Ashishgup consider this seriously . No reason to offend you but codechef is really really bad.
It's unrated — and all short contests on CodeChef are postponed indefinitely until the issues are resolved
First four problems of Div2 were very trivial and completely non-interesting, especially considering the length of 3 hours. Personally, I feel like the difficulty should have been much higher, especially considering that 1st, 2nd and 3rd question barely hit easy D2B here on CF. The last two problems were interesting, but the server issues are gross.
I took half an hour to prove my claim for Division 2-D, and did not find it trivial at the very least after having solved it. Could you share me your approach for this problem?
Hmm, "completely non-interesting" is very subjective, I'm not sure if you're trying to say that your point is objectively correct. I proposed problem 4 (DREDIV) to a few people, and of the 5 people around 2-3 thought it was interesting and the rest thought it was boring. So I don't think it's easy to decide if a task is interesting or not in general. (It's obvious in some special cases, sure, but those are mostly copied problems, and I do think the problem is original)
I like the idea of F, so thanks to the author.
It was unfortunate that my solution has a worse complexity or bad constant factor and I had to constant-optimize the solution, without the knowledge of how fast my code runs on Codechef servers. My latest submission runs in 1.3s in the worst case on my computer. Hope it'll pass after getting evaluated.
Can you describe your solution ?
When you add the $$$i$$$-th student, the expected increase of the score is $$$(i-1)/g$$$. After some calculations (I'll omit the detail because that's complicated), it turns out we need the first $$$O(N)$$$ terms of the FPS of the $$$\sum_{1 \leq k \leq N} \prod_{1 \leq i \leq k} x/(i-(i-1)x)$$$. We can do this by FFT and D&C, and the total complexity is $$$O(N\log ^2N)$$$.
First time able to solve all 6 problems of Div2. Thanks to Codechef and Ashishgup for nice problem set, really enjoyed the contest.
Thank you :D
Lol, my verdict came as internal server error: link
This is the same code i submitted after the contest: link
Ashishgup can you have a look at this, the submission was during contest period only.
Yes, there was some issue with the judge today — occasional submissions got Internal Server Error. We'll look into resolving it before the next contest. Today's contest is unrated.
Why are you guys making it unrated? I wasted my 3 hours. If you could make cook-off rated, then why not this?
CookOff had site issues at the beginning — Lunchtime also had queue issues (30+ minutes at the very end) and issues regarding some Div3 participants not being able to submit their code. It sucks, but hopefully, it does not happen again in the future.
At least, you can make it rated for div 1. Although, I had bad experiences is both cook-off and lunch time, but my experience in lunch time was still better than cook-off and I believe div 1 participants are not much affected. Rest is your decision.
CodeChef_admin
Agreed, this is disappointing. It's the same for everyone. I admit I am biased as I had a good contest was hopefully on track to go up to Div 1. It seems that server issues are commonplace on Code Chef — are all contests going to be unrated until this is resolved? I'm not convinced this is the answer.
No, CodeChef is not going to have a rated contest till the issues are resolved and a testing round is held. So yeah, hopefully, it will be resolved the next time a short contest is held.
Ok, fair enough. Good luck sorting the issues out. I'm sure lots of people are complaining, but hosting contests for others is good and requires a lot of effort, so thanks and I hope you can resolve the server problems.
First time I was able to solve 5 problems in div 2 and contest is made unrated :(
Could you share your approach for Div 2 E?
If we can find two divisors of k such that both are less than equal to n then answer is yes else no.
As a 6-star(2478), where is my 7th star...? (It seems that there are only few troubles in Div1...)
+
We positive deltas may be biased, but in div1 I didnt face much trouble with queue tbh (2-5 mins queue time on each submission)
True that, but in my experience, I encountered many errors while submitting and each time it took like 5-7min to submit the code.
Errors weren't an issue for me, I'd just open like 5 submit tabs at once and atleast one of them would work and I'd be able to submit
Yes Ashishgup in div1 we didn't faced much problems.
Is there any outside chance for Div 1 being rated? Given that we really didn't face much issues atleast in div 1.
Just a friendly suggestion upcoming. In one of the questions in today's contest, YES/NO was expected as output and in another one, Yes/No was expected. Well, it's kind of confusing I suggest you keep it case insensitive if possible or be consistent in the output of all questions of this form in further rounds.
We will be adding a case-insensitive checker to the default judges soon, so it should not be an issue.
January cookoff was worse than this yet it is was rated. Please either make both rated or both unrated.
I got wa due to this.
Can anyone share their approach for the fifth problem of the second division?
Consider if you have 2 good points, P (x0, y0) and Q (x1, y1). Then P is the max of column y0 and the min of row x0, while Q is the max of column y1 and the min of row y1. Let's think about the points A (x0, y1) and B (x1, y0). We know that P >= B and P <= A. We also know that Q >= A and Q <= B. So we must have A = B = P = Q, otherwise some inequality doesn't hold. This means that the total number of points which are good must be the size of a rectangle in the grid.
Therefore X must be the size of some rectangle in the grid, so it must be the product of 2 numbers between 1 and N.
Solution: find factor pairs of X. If there is a pair such that both are between 1 and N, X is reachable, otherwise it is not.
Other things aside, I just want to appreciate the hard-work that Ashishgup and others put in to prepare these contests. I feel that it takes a lot of effort, and it goes unnoticed and gets buried below the shortcomings.
Well, 13 was really unlucky for me
Anyway, there are still some judgement failed verdicts and they should be rejudged. I cannot know the correct ranklist...
Will we still receive our Laddus?
I think if the admin Ashishgup tried to increase the time limit for 20-30 minutes more then it would we fairly possible to have a rated lunchtime :(
Is editorial published?