Using VB6 I have created an array using numbers (from 0 - 24). I want to
randomize the numbers to fill the array but if a duplicate number is
generated by the random function, disregard that number and go on to the next
until I have 10 unique numbers. Any help would be greately appreciated.

BobbyS wrote:
Has the teacher suggested any potential methods to solve this?

Egad, if I just gave someone the answer to a homework question, kick me.

Jeff Johnson [MVP: VB] wrote:
<g>

Karl,
You are safe...I am the teacher...But I was given an English class and I
needed some help with this logic to generate random words for spelling test.
Got everything else done..

Thanks.

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I guess we don't have to kick *Jeff* then.  Dammit!  <g>

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MikeD wrote:
LOL!

PPPHHHHBBBBTTTT!!!!

You could create a second array of 25 elements and assign the numbers 0 to
24 to each element. Then, when you generate a random number from 0 to 24,
you use it as an index into this array. If that element holds a valid
number, you use it and then write -1 into that element. If you check the
element and it contains -1, you know you've used it and you move to the next
element to see if it's available (wrapping from 24 to 0 if necessary).

Just off the top of my head.

Air code:

dim found as boolean
dim n as integer
dim rNum as integer
dim count as integer
dim ary() as integer

redim ary(9) as integer

do

    rNum = Int((10 - 0 + 1) * Rnd + 0)   'Int((upperbound - lowerbound + 1)
* Rnd + lowerbound)

    for n = lbound(ary) to ubound(ary)

        if (rNum = ary(n)) then
            found = true
            exit for
        end if

    next

    if not found then

        ary(count) = rNum

            if count = ubound(ary) then
                exit do
            else
                count = count + 1
            end if

    end if

loop

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Just use the code at  http://vbnet.mvps.org/code/helpers/randomarray.htm,
modified for 25 numbers rather than 52 as the demo shows, then only
reference the first 10 of the numbers.  That's the simplest method.
Otherwise, you have to loop and check, which, for small groups of numbers is
fast, could become a problem for a very large array of numbers.  Here's my
crack at this the brute force way; first uncommented to show the size, then
the same routine with comments. But I'd really still opt for the randomarray
page method.


Private Sub Form_Load()

   Randomize

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

   numDistinctValues = 10  'ie in a quiz, number of questions to ask
   numUpperValueMax = 25  'ie in a quiz, number of questions available

   ReDim narray(1 To numDistinctValues)

   For ncount = 1 To numDistinctValues

      gotIt = False

      Do Until gotIt = True

         tmp = Int(Rnd(1) * numUpperValueMax) + 1

         If ncount = 1 Then
            narray(ncount) = tmp
            gotIt = True
         Else

            Do

               For cnt = 1 To ncount

                  If tmp = narray(cnt) Then
                     tmp = Int(Rnd(1) * numUpperValueMax) + 1
                     Exit For
                    Else
                       gotIt = True
                    End If

               Next

            Loop Until gotIt = True

        End If

        If gotIt = True Then narray(ncount) = tmp

      Loop

   Next

  'debug only
   List1.Clear
   For cnt = LBound(narray) To UBound(narray)
      List1.AddItem narray(cnt)
   Next

End Sub


'Commented version with better debug code to show the workings ...
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

  'ie in a quiz, number of questions to ask
   numDistinctValues = 10

  'ie in a quiz, number of questions available
   numUpperValueMax = 25

   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 the number: 41 is the
        'max number, 1 is the min.  To reset
        'the max, change the 41 to the required
        'upper limit.
         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 alread 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 & " 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
                     '----------------------------
                     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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