I'm new in VBA. I want to make a random pick cycle like that:
Let's say I have seven elements in an array(1,2,3,4,5,6,7), each time when I pick one element from the array, the total number of elements will decrease by 1. After picking every element, the array will be reset to what I initially defined (1,2,3,4,5,6,7) and do the random pick cycle again. The result of every cycle should be different.
Is it possible to do that in VBA?
Here's a stateful function that does what you described each time it is called.
Option Base 1
Dim digits, NLeft
Function RemoveDigit() as Integer
Dim Element as Integer
If IsEmpty(digits) or NLeft = 0 Then
digits = array(1,2,3,4,5,6,7)
NLeft = 7
End If
Element = WorksheetFunction.RandBetween(1,NLeft)
RemoveDigit = digits(Element)
digits(Element) = digits(NLeft)
digits(NLeft) = RemoveDigit
NLeft = NLeft - 1
End Function
It uses a well known algorithm to arrange digits in a random order. Basically you choose to swap a random element number with the last element. Then you repeat it on an n - 1 sized array, making it a tail-recursive algorithm (although this implementation of it is not recursive).
Delete this if you want to, but here is a suggestion for a test sub:
Sub TestRemoveDigit()
NLeft = 0
For i = 1 To 7
d = RemoveDigit()
Debug.Print (d)
Next i
End Sub
I think this should do what you're asking for:
Option Explicit
Global vCurrentArray As Variant
Sub ResetArray()
vCurrentArray = Array(1, 2, 3, 4, 5, 6, 7)
End Sub
Sub RemoveElementWithIndex(lIndex As Long)
Dim vTemp() As Variant '* Change the type as needed
Dim lLBound As Long: lLBound = LBound(vCurrentArray)
Dim lUBound As Long: lUBound = UBound(vCurrentArray)
Dim i As Long, v As Variant
Dim blSkipped As Boolean
If lLBound = lUBound Then '* only 1 element
Call ResetArray
Else
ReDim vTemp(lLBound To lUBound - 1)
i = lLBound
For Each v In vCurrentArray
If i <> lIndex Or blSkipped Then
vTemp(i) = v
i = i + 1
Else
blSkipped = True
End If
Next v
vCurrentArray = vTemp
End If
End Sub
Function GetRandomElement() As Variant '* Change the type as needed
Dim lRandomIndex As Long
lRandomIndex = WorksheetFunction.RandBetween(LBound(vCurrentArray), UBound(vCurrentArray))
GetRandomElement = vCurrentArray(lRandomIndex)
RemoveElementWithIndex lRandomIndex
End Function
Sub TestCycles()
Dim lCycle As Long
Dim i As Long
ResetArray
For lCycle = 1 To 3
Debug.Print
For i = 1 To 7
Debug.Print "Cycle: " & lCycle, "i: " & i, "Random Elem: " & GetRandomElement
Next i
Next lCycle
End Sub
Note: There're many ways of achieving the end result. The above is almost a literal translation of your post.
We can not remove a random element from an array. We can redim array to remove last element(s). If you want to remove random element, you can use collection instead like ..
Option Explicit
Sub RemoveRandom()
Dim coll As Collection, cl As Variant, i As Long, j As Long
Set coll = New Collection
For Each cl In Range("A1:A7")
coll.Add cl.Value
Next cl
For j = 1 To coll.Count
i = WorksheetFunction.RandBetween(1, coll.Count)
Debug.Print coll(i)
coll.Remove (i)
Next j
End Sub
