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random shuffle file
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Meir Yan
Ranch Hand
Joined: Apr 27, 2006
Posts: 597
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Hello all
i file with 10000 records and need to shuffle the file so each record
will be set in different place
what is the best way to do it ?
Thanks
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Rob Spoor
Sheriff
Joined: Oct 27, 2005
Posts: 19216
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With a truly random shuffle it is allowed to keep some elements in the same place. In fact, there is a very very slight chance that the order will remain exactly the same.
Check out java.util.Collections, that has some nice methods you can use.
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Paul Clapham
Bartender
Joined: Oct 14, 2005
Posts: 16483
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I'm not sure you really NEED to do that (do you really?), but if you do then you are looking for a derangement. As the article says, the probability that a random permutation of 10,000 records is actually a derangement is pretty close to 1/e.
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fred rosenberger
lowercase baba
Bartender
Joined: Oct 02, 2003
Posts: 9950
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delete the first record, and re-write it on the end. you are guaranteed to not have any element in the same position.
Seriously, it helps to define the problem better.
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Never ascribe to malice that which can be adequately explained by stupidity.
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Vikas Kapoor
Ranch Hand
Joined: Aug 16, 2007
Posts: 1374
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How about generating random number rather than shuffling the actual file records?
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subject: random shuffle file
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