Generating permutations in VBA
Question
This question has been asked before, but I can't find an answer that is easily applicable to Excel VBA.
Basically I want to do exactly what this poster has asked, but in VBA. I want to create an array, n x 2^n, where each line represents a different permutation of n variables which can be either 0 or 1.
I've played around with this for ages, and it's easy enough to do for a set n with loads of loops, but for a variable n I can't find anything that works.
Any code or just suggestions of ways of going about this would be much appreciated!
Solution
This will list the value in column A
Sub EasyAsCounting()
Dim N As Long, M As Long, K As Long
N = Application.InputBox(Prompt:="Enter N", Type:=1)
M = 2 ^ N - 1
For K = 0 To M
Cells(K + 1, 1) = "'" & Application.WorksheetFunction.Dec2Bin(K, N)
Next K
End Sub
EDIT#1
This stores the array in VBA only:
Sub EasyAsCounting()
Dim N As Long, M As Long, K As Long, ary, s As String
Dim J As Long
N = Application.InputBox(Prompt:="Enter N", Type:=1)
M = 2 ^ N - 1
ReDim ary(1 To M + 1, 1 To N)
For K = 0 To M
s = Application.WorksheetFunction.Dec2Bin(K, N)
For J = 1 To N
ary(K + 1, J) = Mid(s, J, 1)
Next J
Next K
'
'display the array
'
msg = ""
For K = 1 To M + 1
For J = 1 To N
msg = msg & " " & ary(K, J)
Next J
msg = msg & vbCrLf
Next K
MsgBox msg
End Sub
OTHER TIPS
Here's one if you're not in Excel and don't have access to the functions. Or if you have a number greater than 511.
Sub MakePerms()
Dim i As Long, j As Long
Dim n As Long
Dim aPerms() As Byte
Dim lCnt As Long
Dim sOutput As String
Const lVar As Long = 4
ReDim aPerms(1 To 2 ^ lVar, 1 To lVar)
For i = 0 To UBound(aPerms, 1) - 1
n = i
lCnt = lVar
aPerms(i + 1, lCnt) = CByte(n Mod 2)
n = n \ 2
Do While n > 0
lCnt = lCnt - 1
aPerms(i + 1, lCnt) = CByte(n Mod 2)
n = n \ 2
Loop
Next i
For i = LBound(aPerms, 1) To UBound(aPerms, 1)
sOutput = vbNullString
For j = LBound(aPerms, 2) To UBound(aPerms, 2)
sOutput = sOutput & Space(1) & aPerms(i, j)
Next j
Debug.Print sOutput
Next i
End Sub