UNIQUE Random Numbers - Microsoft Access Forum


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UNIQUE Random Numbers

Kevin Robertson

5 years ago

I am building an unbound form that will display images when the form opens. I don't want the images to appear in the same order each time the form opens. I am using random numbers to achieve this (1 - 4). How do I ensure there are no duplicates so each of my 4 images displays only once?

This is my code so far:

    Dim ctrl As Control
    Dim QuestID As Long
    Dim QuestImage As String

    Randomize

    For Each ctrl In Me.Controls
        QuestID = Int(Rnd * 4) + 1
        QuestImage = Nz(DLookup("QuestImage", "QuestT", "QuestID=" & QuestID), "")
        If ctrl.ControlType = acImage Then
            ctrl.Picture = CurrentProject.Path & "\Images\Quests\" & QuestImage
            ctrl.Tag = QuestID
        End If
    Next

	Alex Hedley @Reply 5 years ago
Create and array to hold the 4 numbers, then randomly pick one, remove from the array, repeat.

	Adam Schwanz @Reply 5 years ago
You could append the random chosen image to a temporary table and then check if the chosen image exists in the table, re-randomize?

	Adam Schwanz @Reply 5 years ago
Yea, using variables is probably a lot easier then using tables.

	Kevin Robertson OP @Reply 5 years ago
Alex, I tried using an Array but it just set each image to the last element in the array.

	Alex Hedley @Reply 5 years ago
I'd need to try it, can't remember how it works in vba if you have to redim etc, it's been a while. Used to .NET and List etc Can you share what you tried?

Kevin Robertson OP @Reply

5 years ago

This is what I have so far:

    Dim ctrl As Control
    Dim QuestArray(4) As String
    Dim QuestID As Long, X As Long
    Dim QuestImage As String

    QuestArray(0) = 1
    QuestArray(1) = 2
    QuestArray(2) = 3
    QuestArray(3) = 4

    For Each ctrl In Me.Controls
        For X = 0 To 3
            QuestID = QuestArray(X)
        Next
        QuestImage = Nz(DLookup("QuestImage", "QuestT", "QuestID=" & QuestID), "")
        If ctrl.ControlType = acImage Then
            ctrl.Picture = CurrentProject.Path & "\Images\Quests\" & QuestImage
            ctrl.Tag = QuestID
        End If
    Next

	Alex Hedley @Reply 5 years ago
For X = 0 To 3 QuestID = QuestArray(X) Next That's always going to loop finish on `QuestID = QuestArray(3)` then continue on. Instead I'd get a random number between 0-3 or 1-4 then get that index from the array, then remove from the list, then random again until all are taken

	Kevin Robertson OP @Reply 5 years ago
Thanks. I'll have to spend some time researching.

Richard Rost @Reply

5 years ago

Here's what I got:

Private Function InArray(NumArray() As Long, R As Long) As Boolean

    Dim X As Long

    For X = 0 To 3

        If NumArray(X) = R Then

            InArray = True

            Exit Function

        End If

    Next

    InArray = False

End Function



Private Sub HelloWorldBtn_Click()

    Dim NumArray(4) As Long, X As Long, Y As Long, R As Long

    Randomize

    StatusBox = ""

    ' Initialize Array

    For X = 0 To 3

        NumArray(X) = 0

    Next

    ' Load Array

    X = 0

    While X < 4

        R = Int(Rnd * 4) + 1

        If Not InArray(NumArray(), R) Then

            NumArray(X) = R

            X = X + 1

        End If

    Wend

    ' Display Array

    For X = 0 To 3

        Status "X: " & NumArray(X)

    Next

End Sub

Just drop that into the TechHelp Free Template if you want to use my StatusBox.

Did I win?

	Richard Rost @Reply 5 years ago
I don't think I've covered passing an ARRAY to a function. You can see it's not hard, but that's the easiest way to verify if the value is in the list of already chosen numbers.

	Kevin Robertson OP @Reply 5 years ago
Thank you Richard. Working beautifully :)

	Richard Rost @Reply 5 years ago
You're very welcome.

	Alex Hedley @Reply 5 years ago
Worth adding to the code vault?

	Richard Rost @Reply 5 years ago
Can't say I'd ever need it again. I just saw a challenge and cranked it out in a few minutes. :)

	Juan C Rivera @Reply 5 years ago
May be worth making it a tech help video

	Richard Rost @Reply 5 years ago
Yeah... I'll add it to the list... but again this is such a specific example that I can't see many people needing it. Prove me wrong. :) What other instances in real life could you see this situation happening?

	Adam Schwanz @Reply 5 years ago
You could want your computer to pick your winning Lotto Powerball numbers ;).

Juan C Rivera @Reply

5 years ago

Adam dont say that Richard might just pull that off. Then he will take off to Bora Bora and drink margaritas all day. LOL The only thing I can think off is lets say you have a database and onit is a random pirture for advetising. Or on your free template you can have a small picture with a link to a tech help videos say random 4 most downloaded. A winning lotto will be or a BINGO Game where random numbers are generated and puts it under the right lettre? WOW let me stop Butelo Expresos are kicking in. Later guys.

Juan
LLNP

	Adam Schwanz @Reply 5 years ago
A Bingo game sounds fun to make, just have it generate the next random number and use if/then to put the letter depending where the number falls. You could probably make all sorts of "games". Make a minesweeper game and have it pick the block numbers for mines randomly :). Then you'd get into a lot more having to code if a surrounding block was one of the numbers chosen and display that number.

	Alex Hedley @Reply 5 years ago
I wouldn�t pick an NP-Complete problem! Saw a great talk at a local Meetup https://github.com/stevenwaterman/Minesweeper-Optimisation Solving Minesweeper in Polynomial time: a talk written before learning that minesweeper is NP-Complete https://github.com/stevenwaterman/Minesweeper-Constrained

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