On Apr 13, 2009, at 7:58 PM, Eric E. Dolecki wrote:
For an example I might want to generate numbers from 1 to 10 over
and over.
All I want to do is when I generate a new number is not allow it to
equal
the previously held value. I can imagine a few approaches but I just
wanted
to make sure I was using the most accepted way of doing it.
Coming in late to this thread...
Personally, for all things random, I now use the Mersenne Twister
algorithm. You can license that for free; just put in the specified
acknowledgement text somewhere in your app/docs.
And, for shuffling, I use the Fisher-Yates algorithm.
For the specific problem above, you sort of have a "modified pick
without replacement" scenario.
Assume you start with an array of 10 values where the values are set
from 1 to 10.
The first time you pick a number, you randomly generate the index of
the number (so 0..9).
That first value then becomes "picked". Your array is then modified
to contain the 9 remaining values.
The 2nd, 3rd, etc. time you pick a number, you basically just pick
from the nine remaining indexes. Then, put back the item you picked in
the previous iteration and pull out the item you picked this iteration.
___________________________________________________________
Ricky A. Sharp mailto:rsh...@instantinteractive.com
Instant Interactive(tm) http://www.instantinteractive.com
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