Hello Codeforces Community!
Wish you all a very Happy New year! Along with the celebrations we are beginning with our first contest of the year, the CodeChef January Long Challenge. The contest will go on for 10 long days. So, you have ample of time to participate, learn and code in the contest. Go ahead and check out the contest details below:
- Joining me on the problem setting panel are: maksym (Maksym Bevza), PraveenDhinwa (Praveen Dhinwa), mgch (Misha Chorniy), xennygrimmato (Vaibhav Tulsyan), sidhant (Sidhant Bansal), Sereja (Sergey Nagin), kevinsogo (Kevin Atienza), satyaki3794 (Satyaki Upadhyay).
- Contest Admin: PraveenDhinwa (Praveen Dhinwa)
- Tester: iscsi(Istvan Nagy)
- Russian Translator : CherryTree (Sergey Kulik)
- Mandarin Translator: huzecong (Hu Zecong)
- Vietnamese Translator: VNOI Team
Please feel free to provide the feedback about the problems in the comments.
Start Time: 06th January 2017 (1500 hrs) to 16th January 2017 (1500 hrs). (Indian Standard Time — +5:30 GMT) — Check your [https://www.timeanddate.com/worldclock/fixedtime.html?msg=January+Challenge+2016&iso=20170106T15&p1=44).
Details: https://www.codechef.com/JAN17
Registration: You need to have a CodeChef handle to participate. For all those, who are interested and don’t have a CodeChef user handle are requested to register in order to participate.
Prizes:
For Global participants:
1st prize: $400 2nd prize: $300
For Indians:
1st prize: INR 12000 2nd prize: INR 8000
In addition to the above prizes. Top 10 global, Top 20 Indian, Top 5 school (Indian), Top 5 school (Global), Top 3 challenge problem solvers Indian and Global (apart from the winners) and top 5 girl coders (given that they are among top 100 in the final rank list — this will be irrespective of the region) will get CodeChef laddus, 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 [email protected])
On top of all it promises to deliver on an interesting set of algorithmic problems with something for all.
Good Luck! Hope to see you participating!!
First I want to tell that tasks were very interesting to me and I spent good time for solving it. Hope to continue to have good tasks with nice ideas behind them.
BUT BUT BUT BUT
I can not like way how that tasks are prepared and your fcking way to not answer on questions.
Task with circles:
I solved it in complexity O(n3 logn), certainly it deserves more than 35 points, you should include that substask, but also it doesn't desrve whole score... Simply I told to not check some cases, which is wrong, and I got full score — testdata is very weak and I believe at least 30% of coders got full score on similar way https://paste.ubuntu.com/23821716/
Normally I wouldn't talk much about this, it's happens, just be more careful next time.
Task with digits separation:
I solved this task on good way, I had very good time 0,02 sec. But again testcases were very weak. Just look at my calc1 function https://paste.ubuntu.com/23821729/ It is not a little difference in time, it is really big difference. It the worst case 300 times slower than it should be ! It can not pass, simply it can not. I am sure that 30-40 % of good submissions again were on wrong way.
Also I spent three days to debug correct code, wrote several solution ! Do you can guess what I changed and it gives AC ?????** printf("%I64d",ans) — > printf("%lld",ans);** Are you joking me???
Fantastic Four task:
I solved task with segment tree, with faster multiplication ( I think the same as you described in editorial) and it wasn't enough! Simply it gives TLE for the last subtask: https://paste.ubuntu.com/23821757/
I do not know what I can optimize anymore. Generally there is no reason to put so big contraints for P and killing brain of users. Also I didn't see any fast submission ( at least 2-3 times above time limit) it means you didn't put proper constraints. Generally best codes should give correct answer at least three times faster than time limit.
Again, I do not have any bad intention and I really like problemset, result is not the most important to me here !
Fantastic Four task: Your faster multiplication typically has 2 or more mod operations that are very costly. You can squeeze to just one as in https://www.codechef.com/viewsolution/12433789 But I agree that the time limit was very tight.
Yep I see, I split on two parts, but again I have a lot of modulos. Definately it is my mistake, but such things shouldn't have made difference between users.