Thread: Best Method
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Dana DeLouis[_3_] Dana DeLouis[_3_] is offline
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Default Best Method

On 3/14/2010 7:14 PM, Dennis Tucker wrote:
What is the best method to make a list of randomized(non-repeating)
numbers between a start value and a end value?



Hi. Just as a side note, the "Best Method" may 'depend' on your size also.
Most algorithms first generate all numbers, then pick unique values.
However, this may be impractical if you have to pick from a size of 1
million. Not quite what I use, but an algorithm may want to branch off
and do something like this if you had to pick 6 numbers from 10,000,000

Sub Demo()
[A1:A6] = WorksheetFunction.Transpose(RandomSample(6, 1, 10000000))
End Sub

Function RandomSample(n, L, H)
Dim d
Dim x

Set d = CreateObject("Scripting.Dictionary")
Do While d.Count < n
x = Int(Rnd * (H - L + 1)) + L
If Not d.exists(x) Then d.Add x, x
Loop
RandomSample = d.keys
End Function


However, your main program would not want to call this routine if you
wanted to pick 100 numbers out of 100. The program would have to loop,
on average, 518 times. Hence, the above would not be efficient.

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HTH :)
Dana DeLouis