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# Invitation to CodeChef April Long Challenge 2018!

Hello Fellow Coders!

Greetings from Chef! Close on the heels of an exciting lineup of contests you all enjoyed, here’s more from Chefland to satisfy your coding appetites in April. This time it’s not a quick snack, it’s a full-course meal with ten days prep time!

I would like to invite you to the April Long Challenge 2018 for 10 days of exciting programming challenges. Joining me on the problem setting panel are:

Please give your feedback on the problem set in the comments below, after the contest.

# Contest Details:

Time: 6th April 2018 (1500 hrs) to 16th April 2018 (1500 hrs). (Indian Standard Time — +5:30 GMT) — Check your timezone.

Registration: You just need to have a CodeChef handle to participate. For all those, who are interested and do not have a CodeChef handle, are requested to register in order to participate.

Prizes: Top 10 global and top 20 Indian winners get 300 Laddus each, with which the winners can claim cool CodeChef goodies. Know more here: https://www.codechef.com/laddu . (For those who have not yet got their previous winning, please send an email to winners@codechef.com)

Good Luck!
Hope to see you participating!!
Happy Programming !!

This question is marked "community wiki".

asked 04 Apr, 18:45

6★mgch
3351124
accept rate: 23%

19.5k348496535

 3 So with this we conclude our April Long Challenge, 2018. We hoped you enjoyed the problems, and will enjoy the editorials as well. Any feedback on problems, editorials, or any other issue is appreciated. We will try our best to improve upon those areas :) If theres anything we can do for you, do let us know. Its been a pleasurable experience for me on the other side of the panel (thanks to the team and @mgch ) and I hope I can say the same for you guys as well :). answered 17 Apr, 16:48 14.5k●1●18●54 accept rate: 18% loved the problems this time around :) (17 Apr, 17:03) 2 Even I loved quite many of them. My favourite was CUTPLANT. AVGPR adn WEIGHTNUM had good concepts involved as well wheich I felt are good for beginners :) (17 Apr, 17:06)
 1 @admin @mgch . I was seeing all submissions page Just after the contest was over. There were submission which were still processing after 3.30 pm. Big queue was there on system. At around 5-6 am. System was taking about 3-4 min to process the result. One suggestion Please don't make the challenge problem such that anyone can atleast get AC. For this contest challenge problem Submissions which simply print A[i]. No processing. Or which print A[i]+k . Were awarded around ~80-90 points. This was the main reason for Big Queue. answered 17 Apr, 16:40 1.8k●3●13 accept rate: 12% I already replied to your query. I will copy it here for documentation purposes :) - @aryanc403- Thats not correct, and wont help. One instance I can give is, that today itself, some guy submitted ≈60 submissions on PyPy, each of which took 20secs to get verdict. A better solution which we suggested what "Limit number of submissions a user can make in X minutes to Y"- i.e. dont allow indefinite submissions for any problem. (17 Apr, 16:45) Yes, this is nice idea. Time duration constraint is okay. Currently we can submit 500 submissions in long challenge. Please don't reduce this limit. One more suggestion this limit can also be on basis of language used. Because PyPy take around 20 sec. So X can be less for PyPy. And C takes less time So X can be greater for C. (17 Apr, 16:54) Yes, I will forward this feedback to @admin for consideration. Dont worry about that :) (17 Apr, 17:06) 3 A simple way of helping the issue is to do something like what is done at the Yandex optimization track, just consider the LAST submission for the final score. This doesn't give the incentive of submitting a lot of times to randomly get a good outcome (since you don't know the full test suite). Rate limiting, while a decent idea, does not alleviate the issue that submitting a random algo a lot of times is beneficial. @admin @aryanc403 @vijju123 (17 Apr, 19:47) algmyr7★ 1 Thats also an idea worth considering @algmyr . Lets see developer's stand on it. :) (17 Apr, 20:00) One more suggestion I have that during long contest wee can have some system reserved(kind of). That they will give priority only to challenge questions and the other way round. Because a person who is submitting around ~60 submission really didn't care about output/points of problems. Just he want to submit same questions with as many random questions as he can. So, some system can give priority to non challenge problems. And other problems soln verdict can be given without much delay. (18 Apr, 03:21) @algmyr, that's a very interesting suggestion. We will discuss about this. Thanks! (18 Apr, 19:39) admin ♦♦0★ @admin Also check out my comment under https://discuss.codechef.com/questions/125323/invitation-to-codechef-april-long-challenge-2018/125673, it expands the idea into a more complete solution, both regarding reverse engineering and spam submissions. (18 Apr, 21:13) algmyr7★ 2 @algmyr what is the sense of having provisional tests there? You can optimize the solution for it and receive overfitting(as saying in ML) and in the end, your time will be wasted cause final tests will be completely different. It almost has no sense of checking the solutions in the contest, am I wrong? I have another suggestion: what if we'll try to use multitests in the challenge(around 50-1000 per test case, different types are combined) and testing will be provided only on 5-10% of data. I guess it will be hard for unfair solutions to get the test data. What do you think about that? (18 Apr, 21:38) mgch6★ 1 Yes, solutions which have $T=1$ are far more prone. With mixed solutions of different kinds, I think we can minimize the issue by a good factor. (18 Apr, 22:21) @mgch Provisional tests would be there only to give a rough indicator of how you stack up. If you have a solution that performs consistently it will also be a decent estimate of your final score, similar to what the visible test is today. Even today you have no idea if the hidden tests are vastly different, you pretty much presume that the visible test is representative already. Also, importantly, you are given the data generation algorithm so that you can generate your own test cases to benchmark your program to see that if performs well in general. (18 Apr, 23:20) algmyr7★ 1 @mgch If you're worried that the provisional test cases are not representative you could always add a few more cases of each type to reduce impact of potential outliers. If the final tests are run after the competition (and only on the final submission) this would still be less computationally intensive than running the full test suite on every submission as it's done today (from what I've understood). What I fundamentally would like to enforce is a separation between sets of test cases so you can't gather information on the point giving tests during the competition. (18 Apr, 23:28) algmyr7★ showing 5 of 12 show all
 1 @vijju123 CHEF VIJJU'S CORNER Nice initiative. Increases the effectiveness of editorial. And helps a lot in overcoming mistakes. answered 17 Apr, 18:58 1.8k●3●13 accept rate: 12% 2 Thank you :D I started this when I wrote ICPC editorials for Amritapuri- to put basically any content which I feel might be useful to some, but couldnt be put in formal section. (I got too many complaints of my editorials being too long and too explanative xD). Chef Vijju's corner, or the unofficial part is a nice place for some light hearted humor, and other approaches and "what if" things. Glad you liked it :) . (After all, I believe my editorials should stand out from rest, shouldn;t they? xD) (17 Apr, 19:09) Yes, they should stand out from rest. (17 Apr, 19:21)
 1 For Documentation. Today as soon as editorial were released. Our @vijju123 were quite active in forum to answer queries of users. This is also a Nice initiative. If we have someone from problem setting panel to resolve our queries. = answered 18 Apr, 00:01 1.8k●3●13 accept rate: 12%
 1 This is to inform you that all the Setter's, Tester's and Editorialist's solutions are successfully linked to the editorials, except for CUTPLANT.(I am in talks over this delay for that editorial, we will look into that). The editorialist solution is commented most (I think all :p ) the time, so you can refer to that in case you have any further doubt. Hope you enjoyed the editorials as much as (or preferably more :p) than the problems. In case there is any further issue accessing solution of any other editorial, except CUTPLANT, do ping me here, we will look into that. With that, I would like to conclude the final announcement for this long with three magical words..... View Content answered 18 Apr, 19:33 14.5k●1●18●54 accept rate: 18%
 0 As an additional reminder- Kindly discuss any issues, clarifications etc. related to problem/problem-statements at COMMENTS section of the problem with the setting panel. Any feedback related to this long should be posted here only - the use of separate threads should be avoided as it makes collecting feedback a mess. Any instance of your code getting public due to online ides like ideone.com is punishable, and you will be penalized with same punishment as that of any regular plagiarist. answered 04 Apr, 20:05 14.5k●1●18●54 accept rate: 18%
 0 If possible , the challenge should be extended just for a day .As we are having Google code jam today. answered 07 Apr, 09:25 31●3 accept rate: 0% Duration of APRIL18 will be extended by one day soon. (07 Apr, 17:09) mgch6★ It really shouldn't matter. GCJ was just for 27 hours. (08 Apr, 16:00) 1 Yes, but we extended APRIL18A from another reason - JADUGAR (08 Apr, 18:03) mgch6★
 0 For 300 laddus rank should be in top-20(Indians) in Division-1 or top-20 in both divisions combined ? answered 11 Apr, 19:06 4★rj25 209●4 accept rate: 0% Div1 afaik. The page there says nothing about div2 top 20. It would be unfair for newly gone div1 guys if they'd get equal prize in div2. Would be undesirable. (11 Apr, 19:55)
 0 why duration of APRIL18 long challenge of div-B is not extended while for div-A it is already extended? @mgch @vijju123 answered 11 Apr, 22:53 70●4 accept rate: 0% Div1 got extension because the problem JADUGAR was split into two, and a new subproblem was added in the newer version, JADUGAR2. This did not affect div2 in any way. However, if you want an extension as well, I can talk to @mgch regarding that- but I need a valid reason to do so. (12 Apr, 02:36)
 0 Because code jam take almost one full day.So many participant cant try problem through out whole day....if you kindly extend it..it will be better...@vijju123 answered 12 Apr, 19:21 70●4 accept rate: 0% I will consult contest admin @mgch over your concern. (13 Apr, 13:38) The contest for Div2 is extended now. It will end on Tuesday with Div1. (13 Apr, 22:42)
 0 thank you @vijju123 answered 13 Apr, 22:50 70●4 accept rate: 0%
 0 when will the editorials get uploaded. answered 17 Apr, 16:18 1●1 accept rate: 0% They already are. (17 Apr, 16:35)
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question asked: 04 Apr, 18:45

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last updated: 20 Apr, 20:25