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Please Note: This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here: Listing Combinations.
Ron knows he can use the COMBIN function to determine the number of combinations that can be made from a number of digits. He's wondering, however, if there is a way to list out all the combinations themselves.
There is no built-in way to list combinations in Excel. You can, however, create a macro to do the listing for you. If you want to find the unique combinations in a set of sequential numbers starting at 1, then the following set of macros will do the trick. All you need to do is run the function TestCNR and you will end up with a "matrix" of cells that represent the number of 4-digit combinations in the sequential set of values ranging from 1 to 10.
Sub TestCNR() Cnr 10, 4 End Sub
Sub Cnr(n, r) i = 1 For j = 1 To r Cells(i, j).Value = j Next Do Until Finished(n, r, i) j = FindFirstSmall(n, r, i) For k = 1 To j – 1 Cells(i + 1, k).Value = Cells(i, k).Value Next Cells(i + 1, j).Value = Cells(i, j).Value + 1 For k = j + 1 To r Cells(i + 1, k).Value = Cells(i + 1, k - 1).Value + 1 Next i = i + 1 Loop End Sub
Function Finished(n, r, i) Temp = True For j = r To 1 Step -1 If Cells(i, j).Value <> j + (n - r) Then Temp = False End If Next Finished = Temp End Function Function FindFirstSmall(n, r, i) j = r Do Until Cells(i, j).Value <> j + (n - r) j = j - 1 Loop FindFirstSmall = j End Function
The macro overwrites whatever is in your worksheet, so make sure you run the test with a blank worksheet displayed. If you want to change the size of the set or the number of elements in the subset, just change the values passed in the TestCNR routine.
If you want to pull unique combinations from a string of characters (for instance, the letters of the alphabet), then you need to use a different set of macros. The following will work fine; it assumes that the characters you want to use as your "universe" is in cell A1 and the number you want in each unique combination is in cell A2.
Sub FindSets() Dim iA() As Integer Dim sUniv As String Dim iWanted As Integer Dim j As Integer Dim k As Integer sUniv = Cells(1, 1).Value iWanted = Cells(2, 1).Value ReDim iA(iWanted) For j = 1 To iWanted iA(j) = j Next j iRow = PutRow(iA, sUniv, 1) Do Until DoneYet(iA, Len(sUniv)) j = WorkHere(iA, Len(sUniv)) iA(j) = iA(j) + 1 For k = j + 1 To iWanted iA(k) = iA(k - 1) + 1 Next k iRow = PutRow(iA, sUniv, iRow) Loop End Sub
Function DoneYet(iB, n) As Boolean iMax = UBound(iB) Temp = True For j = iMax To 1 Step -1 If iB(j) <> j + (n - iMax) Then Temp = False End If Next DoneYet = Temp End Function
Function WorkHere(iB, n) As Integer iMax = UBound(iB) j = iMax Do Until iB(j) <> j + (n - iMax) j = j - 1 Loop WorkHere = j End Function
Function PutRow(iB, sUniv, i) iMax = UBound(iB) sTemp = "" For j = 1 To iMax sTemp = sTemp & Mid(sUniv, iB(j), 1) Next j Cells(i, 2).Value = sTemp PutRow = i + 1 End Function
Run the FindSets macro and the different combinations desired end up in column 2. Be careful when running the macro, however. The number of combinations can get very large very quickly. For instance, if you put 26 letters (A through Z) in cell A1 and the value 5 in cell A2, the macro will crash. Why? Because there are 65,780 possible five-character combinations and only 65,536 rows in which to place them.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (6766) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Listing Combinations.
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