### mohammedehab2002's blog

By mohammedehab2002, 6 weeks ago,

We invite you to participate in the CodeChef October Lunchtime — the 3-hour contest which offers 5 challenging problems to be solved, next Saturday, October 31st, 19:30 to 22:30 IST.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

The members of the problem setting panel are:

Prizes: The top 10 Indian and top 10 Global school students from ranklist will receive certificates and CodeChef laddus, with which they can claim cool CodeChef goodies. Know more here.

Video Editorials: You will now also be able to solve your doubts with the help of our amazing educators and their helpful video editorials. Don't forget to check out our YouTube Channel soon after the contest ends. Hit the Subscribe button so you don’t miss out on any video editorials in the future.

Good luck and have fun!

UPD: Thanks everyone for participating! Here are some quick solution sketches. You can find more detailed editorials on CodeChef.

ANDOR
SUBMEXS
GSUB
COPAR
SSO
CDSUMS
EFLIP

• +157

 » 6 weeks ago, # |   -47 Is it rated?
•  » » 6 weeks ago, # ^ |   -6 Abbey lodu
 » 6 weeks ago, # |   +8 Hope the timing doesn't get changed like the last codechef Lunchtime
 » 6 weeks ago, # |   +38 Congrats on reaching red!
•  » » 5 weeks ago, # ^ |   +5 Aww thank you :D
 » 5 weeks ago, # |   +3 XOR missiles on their way, btw congrats on reaching red
•  » » 5 weeks ago, # ^ |   +2 *number theory missiles
•  » » 5 weeks ago, # ^ |   +12 Thank you :D
 » 5 weeks ago, # |   0 Problem's arranged in sorted order of difficulty ?
 » 5 weeks ago, # |   0 Attending lunchtime contest in dinner time :D
 » 4 weeks ago, # |   0 How to solve Chef Likes Good Sequence ??Have there any way to solve only subtask.1 for Q=1 ??? I tried but failed.
•  » » 4 weeks ago, # ^ |   +5 You are looking for a subsequence not a subarray.HINT: It can be done greedily.
•  » » » 4 weeks ago, # ^ |   0 Thank you sir..subsequence not a subarray its solved the problem <3
 » 4 weeks ago, # |   +6 The video editorials to the problems are uploaded on Youtube
•  » » 4 weeks ago, # ^ |   0 Real CodeChef admin ?
 » 4 weeks ago, # |   -7 Tip for SSO : Use (1LL << n) instead of (1 << n). Off Topic — Nice set of problems <3 .
 » 4 weeks ago, # |   0 Can COPAR be solved using binary search?
•  » » 4 weeks ago, # ^ | ← Rev. 3 →   0 I tried but got WA Submission Test Case55 2 7 11 2
•  » » » 4 weeks ago, # ^ |   0 It looks like, it can be solved with BS.
•  » » 4 weeks ago, # ^ |   0 I don't think it's possible. My reasoning: say l is a valid splitting point, then there's no guarantee that either l + 1 will also be a valid splitting pointEx:2 3 7 49as we can see we can split as : {2, 3} and {7, 49} but not {2, 3, 7} and {49}
•  » » » 4 weeks ago, # ^ |   0 Thanks for pointing out.
 » 4 weeks ago, # |   0 How to solve last problem?
 » 4 weeks ago, # |   0 All problems in division 2 was based on some cool observations and I really liked it. Managed to solve all problems. I personally liked COPAR, cool NT problem.
 » 4 weeks ago, # |   -11 I think that this time, the lunchtime was not balanced and as always the problems were not sorted according to difficulty, which I think should be improved in the further contests.
•  » » 4 weeks ago, # ^ |   0 Why should it be sorted according to difficulty ?
•  » » » 4 weeks ago, # ^ |   0 At least we can know the order of questions so that we can use our time wisely, as Codeforces does.
•  » » » 4 weeks ago, # ^ |   0 Most people who are not that good don't have a sense of how hard the problem so it is good If they are sorted.Sometimes I am not able to solve div2B and there is always a thought in the back of my mind that the problem is not that hard and I do solve after sometimes If problems were not sorted by difficult I would have left them after some time.
•  » » » » 4 weeks ago, # ^ |   +4 Can't you judge the difficulty by the number of solves? There are other contests out there (like ICPC i think) that doesn't order its problems, you just have to find the easiest one to solve. Being able to find the problem you can solve quickest is a skill in itself. Most people who are not that good aren't really under any time pressure to solve fast anyway, so judging by solves is fine. I still do that, because I suck at judging the difficulty of a problem.
•  » » » » » 4 weeks ago, # ^ |   0 agree :)
•  » » » » » 4 weeks ago, # ^ |   0 Fine for probably division 1, not for division 2. Just look at round 679. C was harder than D, even till 1 hour, C had greater number of solves than D. So, some guys tried D late, if they tried early, D could have more solves.ICPC and Olympiads come in mind when people go in div1. So, div2 contests would be sorted by difficulty
•  » » » » 4 weeks ago, # ^ | ← Rev. 3 →   0 The only rush is for the first problem and after like 5 to 10 mins everything is sorted, also when you are in div2 its easy to spot the easy problems. If you can't spot the easy problems use this trickProblems which are additional in div1 are the easiest one for div2. :)
 » 4 weeks ago, # |   0 what's with CodeChef not explaining the sample case and problem statement for Chef Likes Good Sequences was just garbage. I did not understand the question and was not able to solve such an easy problem.
•  » » 4 weeks ago, # ^ |   0 Same for me bro ..I solved the next one which solved less than this :(
 » 4 weeks ago, # |   0 love from bd.