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:
- Setter: Mohammed mohammedehab2002 Ehab
- Tester: Ramazan never_giveup Rakhmatullin
- Statement Verifier: Jakub Xellos Safin
- Editorialist: Ishmeet Singh Psychik Saggu
- Video Editorialists: Chirayu Chirayu Jain, Prachi agarwal19 Agarwal, Darshan darshancool25 Lokhande, Mani manijuana Tyagi, Divesh divesh2201 Thakker
- Admin: Ildar 300iq Gainullin
- Mandarin Translator: Gedi gediiiiiii Zheng
- Vietnamese Translator: Team VNOI
- Russian Translator: Fedor Mediocrity Korobeinikov
- Bengali Translator: Mohammad solaimanope Solaiman
- Hindi Translator: Akash Shrivastava
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.
Hope the timing doesn't get changed like the last codechef Lunchtime
Congrats on reaching red!
Aww thank you :D
XOR missiles on their way, btw congrats on reaching red
*number theory missiles
Thank you :D
Problem's arranged in sorted order of difficulty ?
Attending lunchtime contest in dinner time :D
How to solve
Chef Likes Good Sequence
??Have there any way to solve only subtask.1 for Q=1 ??? I tried but failed.
You are looking for a subsequence not a subarray.
HINT: It can be done greedily.
Thank you sir..
subsequence not a subarray
its solved the problem <3The video editorials to the problems are uploaded on Youtube
Can COPAR be solved using binary search?
I tried but got WA Submission
5
5 2 7 11 2
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 point
Ex:
2 3 7 49
as we can see we can split as : {2, 3} and {7, 49} but not {2, 3, 7} and {49}
How to solve last problem?
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.
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.
Why should it be sorted according to difficulty ?
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.
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.
agree :)
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
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.
Problems which are additional in div1 are the easiest one for div2. :)
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.
Same for me bro ..I solved the next one which solved less than this :(