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### 11001 - Necklace

Posted: Wed Mar 08, 2006 1:06 pm
What does unique mean in this problem

Posted: Wed Mar 08, 2006 1:50 pm
If you have Vtotal=6 and V0=2, you can either make one disk with diameter 0.3*sqrt(6-2) = 0.6, or two disks with diameter 0.3*sqrt(3-2) = 0.3. Both necklaces have the same length (0.6) and therefor the answer is not unique.

Posted: Wed Mar 08, 2006 2:58 pm
Need help! This is what I tried:

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``````
[1] L = n * D = 0.3 * n * sqrt( Vtot/n - V0 )
[2] L' = 0 && L'' < 0 or so on ...
``````
What am I missing?

Posted: Wed Mar 08, 2006 3:23 pm
Nothing much, I think. The function L(n) is well behaved and has real values between it's two zeros n=0 and n=Vtot/Vo, and one maximum, so there is no need to consider the second derivative. Are you sure you don't report a value outside this range where L(n) becomes imaginary?

Posted: Wed Mar 08, 2006 3:52 pm
Thanks!
little joey wrote:... Are you sure you don't report a value outside this range where L(n) becomes imaginary?
Well, I no longer have a way to check it, off-hand. I was so pissed off with
having a WA with this one, I well ... trashed the 20-odd lines.
Hope my previous post isn't a spoiler. Realized it only now

Posted: Thu Mar 09, 2006 10:54 am
so please can anyone explain to me how the second sample input gives a zero at the output ?

Thanks alot

Posted: Thu Mar 09, 2006 11:32 am
In sample case #2, if you either take n=2 or n=3, you'll make a necklace of length 2*0.3*sqrt(10/2-2) = 3*0.3*sqrt(10/3-2) ~= 1.039. That's maximum possible, and since choice of n is not unique you are to print 0.

Posted: Thu Mar 09, 2006 11:51 am
It is interesting to note that we don't need to know the total length to solve this problem. It is sufficient to compare the two candidate values of n and checking certain conditions.

Posted: Sat Mar 11, 2006 3:59 am
Hello there!
I'm getting WA. Could anyone say me why?
Sorry for post my code

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``````EDITED POST
``````

Posted: Sat Mar 11, 2006 4:11 am
Here are some tests:

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``````10 4
10 5
100 50
100 51
60000 600
60000 500
60000 300
42424 543
0 0
``````

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``````1
1
1
1
50
60
100
39
``````
btw, it's possible to solve this problem without floating point computations.

Posted: Sat Mar 11, 2006 4:27 am
thanks for your test cases, I have maked some changes and now get correct answer for your test cases but continue getting WA.
Here is my new code (sorry for posting)

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``````CUT OFF
``````
btw, I will try figure out how solve this problem without floating point computations

Posted: Sat Mar 11, 2006 4:52 am
Output for cases, in which Vtotal = V0 should be 0.

Your program prints 1, and that's wrong according to this:
When V <= V0, no ceramic discs can be made

Posted: Sat Mar 11, 2006 2:10 pm
Thanks mf!
I would must have read the problem more slowly.
I considered that case like a good case.

Posted: Tue Mar 28, 2006 6:10 pm
can anyone post the results of those test cases below:
40000 3
40000 9
50000 3
60000 7
60000 9
60000 11

Posted: Tue Mar 28, 2006 6:56 pm
for the input:

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``````40000 3
40000 9
50000 3
60000 7
60000 9
60000 11
0 0``````
output:

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``````6667
2222
8333
4286
3333
2727``````
Darko