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QuestionSpecify numbers as product of Primes? Pin
Ian Uy25-Jun-08 19:37
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cp987625-Jun-08 21:32
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Ian Uy26-Jun-08 0:42
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Robert.C.Cartaino26-Jun-08 4:48
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Ian Uy26-Jun-08 4:50
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The Developer8-Aug-08 7:03
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Ian Uy26-Jun-08 6:28
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Paul Conrad28-Jun-08 5:44
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Ian Uy28-Jun-08 5:46
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Paul Conrad28-Jun-08 6:11
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Ravi Bhavnani8-Aug-08 7:16
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cp987628-Jun-08 20:27
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GeneralRe: Specify numbers as product of Primes? Pin
Luc Pattyn29-Jun-08 2:42
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MarkBrock27-Jun-08 18:46
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Paul Conrad28-Jun-08 5:42
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ChandraRam2-Jul-08 22:49
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MarkBrock2-Jul-08 23:06
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Member 419459326-Jun-08 8:19
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GeneralRe: Specify numbers as product of Primes? Pin
Robert.C.Cartaino26-Jun-08 8:47
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GeneralRe: Specify numbers as product of Primes? Pin
Ian Uy26-Jun-08 17:51
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cp987629-Jun-08 14:57
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AnswerRe: Specify numbers as product of Primes? Pin
Arash Partow29-Jun-08 0:48
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GeneralRe: Specify numbers as product of Primes? [modified] Pin
cp987629-Jun-08 3:53
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GeneralRe: Specify numbers as product of Primes? Pin
Luc Pattyn29-Jun-08 4:40
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cp987629-Jun-08 14:47
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GeneralRe: Specify numbers as product of Primes? Pin
Arash Partow30-Jun-08 2:54
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GeneralRe: Specify numbers as product of Primes? Pin
cp987630-Jun-08 3:18
membercp987630-Jun-08 3:18 
Arash Partow wrote:
I believe this is not correct, assume you have an x composed from 2p where p is a prime, in this case it is clear that in certain circumstance sqrt(x) can be less than p (eg: 15838 = 7919 * 2, where 7919 > sqrt(15838)), for primal testing the sqrt(n) bound is ok, however its not suitable for the upper bound in this problem.


He's studying for the ACM competition - I don't want to spoon feed him! He can limit his testing to sqrt(N) but he has to modify his algorithm slightly for when InputCase is not 1 at the end.

In the example you give, he only needs to test until floor(sqrt(15838))=125, he will have only found 2 as a factor and InputCase will be 7919 after the 124 tests. He can then conclude the the remaining value in InputCase is the remaining prime factor. This is much more efficient than testing the remaining 15,703 factors.

Peter
"Until the invention of the computer, the machine gun was the device that enabled humans to make the most mistakes in the smallest amount of time."

GeneralRe: Specify numbers as product of Primes? Pin
Arash Partow30-Jun-08 4:27
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Arash Partow30-Jun-08 2:17
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