Randomizing an array - arrays

Question

I wish to implement the Dr.D.E.Knuth's Subtractive RANDOM number generation algorithm. I wish to implement an ATM panel on which when very time user log-in the buttons will be scrambled. every button will change its position.
Here is my code:
Public Sub addbutton()
Dim n As Integer = 0
For i As Integer = 0 To 10
' Initialize one variable
btnArray(i) = New System.Windows.Forms.Button
Next i
While (n < 10)
With (btnArray(n))
.Tag = n + 1 ' Tag of button
.Width = 40 ' Width of button
.Height = 40
FlowLayoutPanel1.Controls.Add(btnArray(n))
.Text = Chr(n + 48)
AddHandler .Click, AddressOf Me.ClickButton
n += 1
End With
End While
End Sub
Then, for sending information to button Text, I used:
Dim btn As Button = sender
TextBox1.Text += btn.Text
Now the major task is to shuffle the btnArray() with Random() function.. But I've failed to do this. I managed to get some code for shuffling the array like follows:
Imports System.Security.Cryptography
Public Class ArrayUtilities
Private Random As RNGCryptoServiceProvider = New RNGCryptoServiceProvider
Private Bytes(4) As Byte
Public Function ShuffleArray(ByVal argArr As Array) As Array
Dim FirstArray As New ArrayList(argArr)
Dim SecoundArray As Array = Array.CreateInstance(GetType(Object), FirstArray.Count)
Dim intIndex As Integer
For i As Integer = 0 To FirstArray.Count - 1
intIndex = RandomNumber(FirstArray.Count)
SecoundArray(i) = FirstArray(intIndex)
FirstArray.RemoveAt(intIndex)
Next
FirstArray = Nothing
Return SecoundArray
End Function
Private Function RandomNumber(ByVal argMax As Integer) As Integer
If argMax <= 0 Then Throw New Exception
Random.GetBytes(Bytes)
Dim intValue As Integer = (BitConverter.ToInt32(Bytes, 0)) Mod argMax
If intValue < 0 Then intValue = -intValue
Return intValue
End Function
End Class
Module Module1
Sub Main()
Dim AU As ArrayUtilities
AU = New ArrayUtilities
Dim GivenArray As Integer() = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
Dim NewArray As Array = AU.ShuffleArray(GivenArray)
Dim i As Integer
Dim stb As New System.Text.StringBuilder
stb.Append("GivenArray = {0,1,2,3,4,5,6,7,8,9}")
stb.Append(vbCrLf)
stb.Append("NewArray = {")
For i = 0 To NewArray.Length - 2
stb.Append(NewArray(i).ToString)
stb.Append(", ")
Next
stb.Append(NewArray(NewArray.Length - 1).ToString)
stb.Append("}")
Console.Write(stb.ToString)
Console.Read()
End Sub
End Module
Yet, when we debug this code we get RANDOMNESS for the array. In the same way, I want randomness for my buttons on form.
Thank you sir. sir i tried the code that u suggested.
I was missing the incremental character "n".
Tthe debug-able code is
flowlayoutpannel.controls.add(out(n)).
but it is not working as i wanted and ABOVE code is just to show the way i want 2 shuffle the BUTTONS.
Is there any simpler way to jst create an button array and randomize them with RANDOM() and adding to form.
My buddies says you are so stupid that u are working on this topic from last 20-25DAYS

Answer 1

There are quite some "shuffle" algorithms (search Fisher-Yates for example) and they are usually not difficult to implement. The EASIEST (imho) way, ist to use LINQ:
Dim r As New Random
Dim out = (From b In btnArray Order By r.Next Select b).ToArray
Maybe the question is not clear: Do you want to shuffle the POSITIONS of the buttons or do you want to shuffle the CONTENT (buttons) of the Array?

Answer 2

To set the position of the buttons randomly in the panel, instead of using n from 0 to 9 in the loop, you can use a random value from 0 to 9. Be sure you don't use the same value twice.

Answer 3

You don't need to use a cryptographically secure random number generator for that, nor do you need a separate class.
Private Shared rng As New Random()
Private Shared Function ShuffleArray(Of T)(arr() As T) As T()
Dim left = Enumerable.Range(0, arr.Length).ToList()
Dim result(arr.Length - 1) As T
For i = 0 To arr.Length - 1
Dim nextIndex = rng.Next(left.Count)
result(i) = arr(left(nextIndex))
left.RemoveAt(nextIndex)
Next
Return result
End Function