### Ashishgup's blog

By Ashishgup, 9 months ago,

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:

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.

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:

1. Petr (900/900 points — only one to solve all problems)
2. kabuszki (810/900 points)
3. 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.

• -39

 » 9 months ago, # |   +10 The top 10 Indian and top 10 Global participants will receive CodeChef laddus Not all participants but only school students because it's a LT, or this time is an exception?
•  » » 9 months ago, # ^ |   0 Only school students as usual I guess.
•  » » 9 months ago, # ^ |   +7 It will be given to both as an exception :D Top 10 users (Indian and Global) Top 10 school students (Indian and Global)
 » 9 months ago, # |   +29 Can we expect another server issues?Because It was very irritating that happened last time
•  » » 9 months ago, # ^ |   -42 Hopefully it's better this time, CodeChef now has more servers to handle the traffic.
•  » » » 9 months ago, # ^ |   -20 The should rewrite their code from php to golang.
•  » » » 9 months ago, # ^ |   +4 The story of every Codechef contest : click
•  » » » » 9 months ago, # ^ |   -24 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 :(
•  » » » » » 9 months ago, # ^ |   +24 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.
•  » » » » » » 9 months ago, # ^ | ← Rev. 2 →   0 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 issuesPlease take some time to resolve this issue..This is really frustrating : (
•  » » » » » 9 months ago, # ^ |   0 I am getting rid from Codechef every time trouble happen .
 » 9 months ago, # |   0 No subtasks :(
•  » » 9 months ago, # ^ |   -16 Some problems will have subtasks, but yes, most of them do not have it.
 » 9 months ago, # |   +13 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.
•  » » 9 months ago, # ^ |   +4 Good luck :D
 » 9 months ago, # |   +13 Please try to keep the usual timings for future lunchtime contests.
 » 9 months ago, # |   0 Why unusual time?
•  » » 9 months ago, # ^ |   0 As mentioned in the blog, it was to avoid the clash with Codeflows Finals which ended at 8:30PM IST.
 » 9 months ago, # |   +3 What does "replay of Codeflows" means? The problems will be same as Codeflows?
•  » » 9 months ago, # ^ |   +5 Some problems are shared, some are exclusive to LTIME — but yes, most of the harder problems are same as Codeflows.
 » 9 months ago, # | ← Rev. 2 →   +14  ByteDance is joining CodeChef as the official contest recruiter! 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 :)
 » 9 months ago, # |   -30 Reminder: Contest starts in 5 minutes.
 » 9 months ago, # |   +14 I think server are down again .Problems are not loading
 » 9 months ago, # |   +5 Here we Go again
 » 9 months ago, # |   +9 I can't submit lol
 » 9 months ago, # |   +5 Long Queue again :(
 » 9 months ago, # |   +5 Cannot submit due to error . Waiting from 4 minutes.
 » 9 months ago, # |   +5 server started crashing wow!!
 » 9 months ago, # |   0 if this contest will become unrated i have to leave codechef foreever :_)
•  » » 9 months ago, # ^ |   0 Servers just crashes in the starting hour of contest and everyone knows even 1 minute of time penalty gets you punished in ranking. The same happened in dec and jan cook off and then I stopped using it since last week. glad that I didn't participate today. They have the same story every time.
•  » » » 9 months ago, # ^ |   0 yeah..but they somehow managed to fix the server!!!
•  » » » » 9 months ago, # ^ |   0 Fixing the server is okay, but in cookoffs its too irritating that you can't even submit the solution in a time based contest, sometimes servers works for a moment where somebody else submit the solution and you can't because either you were solving some other problem or you IDE didn't initialize. Forget about queues.
 » 9 months ago, # |   0 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.
•  » » 9 months ago, # ^ |   0 I'm not even able to submit : (
 » 9 months ago, # |   -7 This is shameful from CodeChef.
 » 9 months ago, # |   +20 Such a time waste to participate in Codechef Contests nowadays.
 » 9 months ago, # |   -9 bruh
 » 9 months ago, # |   +7 Leave Codechef!!!
 » 9 months ago, # |   0 Maybe this happens because the easy problems are way too easy and a lot of people submit
 » 9 months ago, # |   +3 :(
 » 9 months ago, # | ← Rev. 2 →   -10 503 server error has become constant state of life for codechef
 » 9 months ago, # | ← Rev. 2 →   -18 Its common for codechef these days to hold contest just to disappoint people
•  » » 9 months ago, # ^ |   +15 ok
•  » » 9 months ago, # ^ |   +19 ok
•  » » » 9 months ago, # ^ |   +22 ok
•  » » » 9 months ago, # ^ | ← Rev. 2 →   0 well, sincerely i said ok just because i look that I will gaining contribution but it seems that was negative.. :'(
•  » » 8 months ago, # ^ |   0 ok
 » 9 months ago, # |   0 Ashishgup I am not able to submit. Its shows 404 error. Make the round unrated.
•  » » 9 months ago, # ^ |   0 rip
•  » » 9 months ago, # ^ |   0 He made it unrated for u <3
 » 9 months ago, # |   0 Bro how many server codechef have ?
•  » » 9 months ago, # ^ |   -6 half
•  » » » 9 months ago, # ^ |   0 lol, do some research before posting its actually double
•  » » 9 months ago, # ^ |   +9 same as number of living dinosaur in 20th century
 » 9 months ago, # |   -9 Having a little tougher or more tricky questions would be better as it means less submisions at once and less load on server at any given point of time.
 » 9 months ago, # |   +19 sigh this is really the fourth time in a row :|
 » 9 months ago, # |   +16 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?
 » 9 months ago, # | ← Rev. 3 →   -45 .
•  » » 9 months ago, # ^ |   +24 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.
•  » » » 9 months ago, # ^ |   +13 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.
•  » » » » 9 months ago, # ^ |   -8 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.
•  » » 9 months ago, # ^ | ← Rev. 2 →   +9 At the bottom of the problem page there is a section of comments, you can ask there.
 » 9 months ago, # |   +4 When submitting a solution is harder than solving the problem.
 » 9 months ago, # |   0 my submission is on queue since hour.
•  » » 9 months ago, # ^ |   +6 I don't think there is any queue issue (2-3 mins atmax?) — can you link your submission?
•  » » 9 months ago, # ^ |   +13 I don't think so...three solution got accepted in less than an hour.
•  » » » 9 months ago, # ^ |   +1 damn bro u livin in 2031
•  » » » » 9 months ago, # ^ |   0 I'm not lying... you can check out my recent submission. Here
•  » » » 9 months ago, # ^ | ← Rev. 2 →   0 Nice meme. Spoiler"""three solution got accepted in less than an hour."""
 » 9 months ago, # |   0 I think in this contest ranking should be based on how many problems were solved by contestant rather than how fast they solve. As we can clearly see that servers are not working properly and people are not able to submit them . To compensate , Admin you should consider about it.
 » 9 months ago, # |   0 Has website stopped loading ? In my case i am not able to load the website itself currently .
•  » » 9 months ago, # ^ |   0 It's working
•  » » » 9 months ago, # ^ |   0 yeah just started again.
•  » » » 9 months ago, # ^ |   0 unable to submit problem now, stuck on choosing language and unable to choose language either. tried from diff. browser but issue persists.
 » 9 months ago, # | ← Rev. 2 →   0 its working
 » 9 months ago, # |   +1 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
•  » » 9 months ago, # ^ |   0 I'll ask the CodeChef team to check
•  » » » 9 months ago, # ^ |   0 yes me too facing the same problem in div 3
•  » » » 9 months ago, # ^ |   0 Now it is working , Thanks!
•  » » 9 months ago, # ^ |   0 I thought that I spam submit a lot so they remove the laguage selection to not let me submit again LMAO :))
 » 9 months ago, # |   0 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 .
•  » » 9 months ago, # ^ |   0 It's $p \neq q$, sorry.
 » 9 months ago, # |   0 20min queue for problem D
•  » » 9 months ago, # ^ | ← Rev. 4 →   +3 click My submission -> Then click -> view on your queued submission. Hope you can able to see the verdict.
 » 9 months ago, # |   0 Waiting for judging from 20 mins :(
 » 9 months ago, # | ← Rev. 2 →   0 My submission is running for past 30 minutes @Ashishgup :/
•  » » 9 months ago, # ^ |   0 goto that problem, then goto my submissions. THen refresh. You probably should be seen your verdict there.
•  » » » 9 months ago, # ^ | ← Rev. 2 →   0 Lol. I am obviously checking both the pages.. All my submissions around 11:20-25 are in queue. I think the queue is too long
 » 9 months ago, # |   +12 503 for submit page 4 mins before the end! Really?
•  » » 9 months ago, # ^ | ← Rev. 2 →   +4 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.
•  » » 9 months ago, # ^ |   0 I got 1 minute before :/ .
•  » » 9 months ago, # ^ | ← Rev. 2 →   +3 Middle click submit 10 times, it'll open 10 tabs out of which atleast 1 will work. This is what i do
 » 9 months ago, # |   +29 People here complain to Ashishgup as if he is the owner of Codechef :DChill please. Guy is doing God's work if you ask me.
•  » » 9 months ago, # ^ |   -12 guy is doing codechefs work. are u implying codehef = god
•  » » 9 months ago, # ^ |   0 People just want him to know about the issues they faced as he might be able to get in touch with admin regarding this.
 » 9 months ago, # |   -17 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.
•  » » 9 months ago, # ^ |   +5 If the contests are held like this then I am not sure when will I get it back.
•  » » » 9 months ago, # ^ |   0 I have also attended to it. Honestly i have tried to submit 10 — 12 times. But it was constantly showing error. BUt finally i was able to submit it. Its just a matter of some time. Just keep patience.
•  » » 9 months ago, # ^ |   0 1.They get paid for it . 2.Questions will remain for practice with their name in bottom for forever and thus their effort won't be wasted.Accept it , codechef is really bs.
 » 9 months ago, # |   -8 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.
•  » » 9 months ago, # ^ |   +12 It's unrated — and all short contests on CodeChef are postponed indefinitely until the issues are resolved
 » 9 months ago, # |   -11 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.
•  » » 9 months ago, # ^ |   0 Trivial is subjective. I scratched my head over problem #4 for more than an hour and did not get even close to solving it.
•  » » 9 months ago, # ^ |   +4 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?
•  » » 8 months ago, # ^ | ← Rev. 2 →   +5 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)
 » 9 months ago, # |   +32 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.
•  » » 9 months ago, # ^ |   0 Can you describe your solution ?
•  » » » 9 months ago, # ^ |   +8 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 $O(N\log ^2N)$.
 » 9 months ago, # |   +11 First time able to solve all 6 problems of Div2. Thanks to Codechef and Ashishgup for nice problem set, really enjoyed the contest.
•  » » 9 months ago, # ^ |   0 Thank you :D
 » 9 months ago, # |   +1 Lol, my verdict came as internal server error: linkThis is the same code i submitted after the contest: linkAshishgup can you have a look at this, the submission was during contest period only.
•  » » 9 months ago, # ^ |   +7 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.
 » 9 months ago, # |   +52 Why are you guys making it unrated? I wasted my 3 hours. If you could make cook-off rated, then why not this?
•  » » 9 months ago, # ^ |   0 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.
•  » » » 9 months ago, # ^ |   +40 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
•  » » » » 8 months ago, # ^ |   0 Most of the time in cook-off it was server issue and last minute fix .still it was rated!! and in lunchtime last minute server issue 3hr wasted .contest unrated!!
•  » » 9 months ago, # ^ |   +15 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.
•  » » » 9 months ago, # ^ |   +1 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.
•  » » » » 9 months ago, # ^ |   +14 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.
 » 9 months ago, # |   +9 First time I was able to solve 5 problems in div 2 and contest is made unrated :(
•  » » 9 months ago, # ^ |   0 Could you share your approach for Div 2 E?
•  » » » 9 months ago, # ^ |   0 If we can find two divisors of k such that both are less than equal to n then answer is yes else no.
 » 9 months ago, # |   +75 As a 6-star(2478), where is my 7th star...? (It seems that there are only few troubles in Div1...)
•  » » 9 months ago, # ^ |   +22 +
•  » » 9 months ago, # ^ |   +15 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)
•  » » » 9 months ago, # ^ |   0 True that, but in my experience, I encountered many errors while submitting and each time it took like 5-7min to submit the code.
•  » » » » 9 months ago, # ^ |   +14 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
•  » » » 9 months ago, # ^ |   +20 Yes Ashishgup in div1 we didn't faced much problems.
•  » » 8 months ago, # ^ |   +22 Is there any outside chance for Div 1 being rated? Given that we really didn't face much issues atleast in div 1.
 » 9 months ago, # |   +26 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.
•  » » 9 months ago, # ^ |   +8 We will be adding a case-insensitive checker to the default judges soon, so it should not be an issue.
•  » » » 9 months ago, # ^ |   +12 January cookoff was worse than this yet it is was rated. Please either make both rated or both unrated.
•  » » 9 months ago, # ^ |   0 I got wa due to this.
•  » » » 8 months ago, # ^ |   +1
 » 9 months ago, # |   0 Can anyone share their approach for the fifth problem of the second division?
•  » » 8 months ago, # ^ | ← Rev. 2 →   0 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.
 » 9 months ago, # | ← Rev. 2 →   +20 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.
 » 8 months ago, # |   +2 Well, 13 was really unlucky for me
 » 8 months ago, # | ← Rev. 2 →   +16 Spoiler
 » 8 months ago, # |   0 Anyway, there are still some judgement failed verdicts and they should be rejudged. I cannot know the correct ranklist...
 » 8 months ago, # |   -13 i dont know why i am wasting my time in this shitty codechef!!Thought i will rank up in this contest so gave my time for this contest and managed to solve 4 problem !! and guess what it is unrated!.(i am not against for making this contest unrated becasue many people cant submit properly...i am against this site and this poor server..)
 » 8 months ago, # |   +41 Will we still receive our Laddus?
 » 8 months ago, # |   +3 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 :(
 » 8 months ago, # |   0 How to approach Problem E?
 » 8 months ago, # |   +5 Is editorial published?
 » 8 months ago, # |   0 Video editorials for 8 problems have been uploaded here. And the editorials will be published soon.