 Although
my preference for creating a randomized array of numbers is the method
listed under Related above, there may be occasions where you want to use
brute force to create a specific random array on the fly. The code shown
here takes two values -- one representing the number of unique values
you require, and the second representing the size of the pool to draw
from, e.g. generate 12 unique numbers from 1 to 50 (as shown here).
The
code is copiously commented, resulting in the output shown in the
illustration. You'll notice that when the third number was
generated it matched an already-generated value in position 1. The code
then generated a new value (38 in this case) and assigned that as the #3
item. Similarly, the code detected dupes for items 9 and 11, and
regenerated new values for those.
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Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright ©1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
' applications, but you may not reproduce
' or publish this code on any web site,
' online service, or distribute as source
' on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Sub Form_Load()
Randomize
Command1.Caption = "Random Numbers w/ No Dupes"
End Sub
Private Sub Command1_Click()
Dim nCount As Long
Dim tmp As Long
Dim cnt As Long
Dim gotIt As Boolean
Dim numDistinctValues As Long
Dim numUpperValueMax As Long
'the number of unique numbers you want
'(in a quiz, this might be the number
'of questions you intend to ask)
numDistinctValues = 12
'the size of the pool to draw the
'unique numbers from (in a quiz,
'number of questions available)
numUpperValueMax = 50
ReDim nArray(1 To numDistinctValues)
List1.Clear
'seed the random number generator to
'assure a unique set of numbers each
'time the routine is run. The current
'system time is fine for this purpose.
Randomize CSng(TimeValue(Time))
'begin count to get numbers
For nCount = 1 To numDistinctValues
'reset flag
gotIt = False
Do Until gotIt = True
'generate a number between 1 and
'numDistinctValues
tmp = Int(Rnd(1) * numUpperValueMax) + 1
'if its the first number just add it
'and set the gotIt flag
If nCount = 1 Then
nArray(nCount) = tmp
gotIt = True
Else
'begin a loop that only ends
'once a new valid number is
'generated
Do
'is it already in the list?
For cnt = 1 To nCount
'compare the current value
'(tmp) to know values
If tmp = nArray(cnt) Then
'it must be there, so
'generate another number
'to try and exit the loop
'----------------------------
'DEBUG:
'show the duplicate number
List1.AddItem " " & nCount & vbTab & tmp & " < this is a dupe of #" & cnt
'----------------------------
'try to generate a different number
tmp = Int(Rnd(1) * numUpperValueMax) + 1
'----------------------------
'DEBUG:
'show the new number
List1.AddItem " " & nCount & vbTab & "new #" & nCount & " >" & tmp
'----------------------------
'found a match, so redo whole loop
'again with new tmp value!
gotIt = False
Exit For
Else
gotIt = True 'no match
End If
Next
Loop Until gotIt = True
End If
If gotIt = True Then
'add to the array
nArray(nCount) = tmp
'----------------------------
'DEBUG:
'show the added number
List1.AddItem nCount & vbTab & nArray(nCount)
'----------------------------
End If
Loop
Next
End Sub
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