while other thinks the contest was well balanced. i think the opposite. see the accuracy fell frm 20% to 5% between 4th and 5th ques. difficulty of prob shld increase gradually (as discussed in @triveni’s post). ,
In an optimization problem, it’s really hard to control score on particular submissions. We focus more on how hard it is to optimize the function and test various solutions to check what’s the max score we can get, i.e. is the function too bad that it’s very difficult to optimize it beyond some easy to get solution.
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The number of successful submissions matter. I am not sure, but what if accuracy takes into your multiple failed solution as well? What matters is its ultimately solvable, irrespective of number of attempts needed.
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I too agree with @abx_2109,probably that was because the alternative solution was much simpler than the desired solution(like bitmask for CHANOQ,greedy for 9th sum),if the memory limit were strict,then it could have been a more balanced contest.
But overall,liked it.
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Yeah, I thought of the solution using bitsets too, but disregarded it thinking the time complexity of the solution is O(N^2/\text{WORD_SIZE}) ~ 6.25*10^8 operations which should give TLE. But I guess codechef judge is quite fast.
@admin This is another "Weak testcases in … " kind of post :p. The testcases of the problem POINPOLY were weak this time. What I did is first, I found the minimum and the maximum y co-ordinate of the vertices of the polygon.Lets say they are miny and maxy. Now, I found all points inside the polygon having a particular y co-ordinate, say d. So I iterated for d from (miny+1) to (maxy-1), and found two intersection points of the line y=d with the polygon.(This is guaranteed that there will be two intersection points, since the polygon is convex and miny < d < maxy.) This I did in O(n) for each d. Once I get the two intersection points at y=d, say (l,d) and (r,d) (l and r will not always be integers, but I manipulated accordingly so that they are inside the polygon, by either taking ceil for left and floor for right.). Now I output all points (x,d) such that l<=x<=r. When I get (N/10) points, I break the loop. This solution has a complexity of O((maxy-miny)*n), but still it passed the 30 pts subtask and got TLE in just one file of the large task. Then I reversed the loop and iterated d from (maxy-1) to (miny+1). This solution got 100 pts. 
. This is slow enough even for the small subtask, only when there are counter-cases for such a solution, which wasn’t. I can make it work even faster by choosing random d in [miny+1,maxy-1]. I think making counter-cases for this solution is hard too. But I will be happier to see a TLE verdict for such solution, so that I come up with a better solution.
Here are the two solutions :-
https://www.codechef.com/viewsolution/17305882 // 30 points, TLE in just one file of large input.
https://www.codechef.com/viewsolution/17305969 //100 points
i did the same thing … but couldn’t find my mistake …
Nice contest!
It would be really great if the search for Submissions for a particular problem allowed you to filter by “pts” as well as Language and Result (All/AC/WA/…). If you want to find the fastest 100pts solution, you may have to check through 100 pages of 10pts solutions first.
Also, it would be nice if the Submissions search showed you the size of the program. So you could look for short programs, which could be helpful if you wanted to find the cleanest / most instructive answer. (I suppose this would be controversial, since it would give a little extra information during a contest, but it could be interesting/encouraging to know if there is a short solution.)
If the Submissions search allowed you to download the results as a csv file or something, then people could make their own views of the solutions, e.g., a scattergram of (speed,size).
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The ranklist has totally changed ,and that too after updation of ratings.
Here is the ranklist: https://www.codechef.com/rankings/FEB18
Is this a bug or rating would be updated as per the new ranklist?
The Competition was very well balanced!! One of the best long challenges till date!!
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I really didnt’t think of an alternate solution for CHANOQ and that too by bitsets and a lot of people did it that way. Overall I too liked the contest.
The admin is checking for any issues(if any).It is because of the change in scores of the challenge problems. Probably the testcases or the scoring function of the testcases after the contest is inconsistent with the pre-cases which were provided before the contest ended because the rankings have changed drastically.
So will the ratings be updated?
Thanx for ur reply!!
The ratings will be updated again if some error or inconsistency is found either in the testcases or the scoring function.
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Isnt it unfair? I mean people would obviously try to code in order to get high score in pre tests. Changing the scoring function,or some totally different test cases doesnt seem fair to me.
They didn’t change anything intentionally, probably some fault has occured in the main tests which will be resolved and the ratings will be updated accordingly.
Ooh sorry,i think i misread ur comment.
Thanx!!
It was an amazing contest. Well balanced and each question was interesting. 4th question was tricky and based on observations . I love this type of questions. Enjoyed a lot:)
Thanks