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Feedback Of February Challenge 2018

Hi Fellow Programmers,

The Feb long challenge has just concluded. We hope that you enjoyed participating in the contest. Please feel free to pitch in your views about anything that you would like to mention about the contest.

Regards,
CodeChef Admin

asked 12 Feb, 15:12

admin's gravatar image

0★admin ♦♦
19.3k348495534
accept rate: 36%

3

The difficulty level was quite balanced and good. Finally a nice long contest after long.

(12 Feb, 18:06) vijju123 ♦5★
2

@vijju123 @admin The accounts tanujyadav997 and tanujyadav97 look suspicious. The latter account has deliberately badly indented code and in CLANDLABL only variables are changed.

(14 Feb, 11:14) avi2244★

« previous123next »

Very nice.Enjoyed it a lot!

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answered 12 Feb, 17:43

devansh1497's gravatar image

3★devansh1497
112
accept rate: 0%

One of the best long challenges I've ever taken. Well balanced and nice problems.

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answered 12 Feb, 18:08

orlon's gravatar image

4★orlon
382
accept rate: 0%

Answer is hidden as author is suspended. Click here to view.

answered 13 Feb, 00:23

sundarlal12's gravatar image

1★sundarlal12
(suspended)
accept rate: 0%

Answer is hidden as author is suspended. Click here to view.

answered 13 Feb, 00:25

sundarlal12's gravatar image

1★sundarlal12
(suspended)
accept rate: 0%

plz provide official editorial .... quite good contest!!

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answered 13 Feb, 00:26

abhi007rider's gravatar image

2★abhi007rider
122
accept rate: 0%

They are already out. Please check the forum.

(13 Feb, 00:40) vijju123 ♦5★

@admin @vijju123

Check my soln https://www.codechef.com/viewsolution/17395501 for (Challenge) Biased Committee https://www.codechef.com/FEB18/problems/BIAS

I have been awarded ~20 pts for sinply printing what is given as input. Indeed weak test cases. Such an unoptimized soln got 20 pts and pass subtask 1 of Chef and odd queries awarded 10 pts. Plz don.t allow this type of soln to take away 20 pts on challenge question. As it reduces the moral of other participants when they get to know this.

And they are trying hard to get 100 pts. Or not attempting just because they cannot think of procedure to solve Q.

On the other hand people are getting pts for simply printing input. And that too 20 pts.

This type of soln deserves less than 5 pts. So plz make sure from next time that score should be such that this does not happen again. Because this affects rating and ranking of many deserved ones.

There are many this type of soln. https://www.codechef.com/viewsolution/17425539 https://www.codechef.com/viewsolution/17425340

P.S. Most soln with time ~.012 sec on c/c++. Have either done this or took average.

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answered 13 Feb, 00:43

aryanc403's gravatar image

4★aryanc403
1.7k313
accept rate: 12%

I asked @admin to look into your feedback.

(13 Feb, 13:18) vijju123 ♦5★
4

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.

(13 Feb, 14:22) admin ♦♦0★

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). ,

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answered 13 Feb, 13:38

ganesh35's gravatar image

1★ganesh35
211
accept rate: 0%

1

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.

(13 Feb, 16:58) vijju123 ♦5★

@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. :p . 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

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answered 13 Feb, 19:42

amandeep224's gravatar image

5★amandeep224
01
accept rate: 0%

i did the same thing .. but couldn't find my mistake ..

https://www.codechef.com/viewsolution/17432565

(13 Feb, 19:50) worldunique3★

@alexthelemon can u explain ur method how u solve poinpoly

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answered 13 Feb, 20:05

albert_012's gravatar image

2★albert_012
-15
accept rate: 0%

@admin Please move problems to practice area as soon as contest ends. Its really cumbersome to check frequently whether problems have been moved so that some of us can submit our solutions after the contest.

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answered 13 Feb, 21:23

ak_d's gravatar image

4★ak_d
1
accept rate: 0%

Problems in long challenge are moved to practice area automatically at the end of the contest.

(14 Feb, 08:50) avi2244★
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question asked: 12 Feb, 15:12

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last updated: 15 Feb, 03:39