Resorting Arrays - arrays

Question

I receive data that I need to output in a string of the format:
123 - A, B, C
234 - A
345 - B
567 - B, C
789 - C
The data I get is sorted by letter (A, B, or C) and then given to me by number. So I have three dynamic arrays like:
ArrayA(1) = 123
ArrayA(2) = 234
ArrayB(1) = 345
ArrayB(2) = 123
ArrayB(3) = 567
ArrayC(1) = 123
ArrayC(2) = 789
ArrayC(3) = 567
Notice that the index corresponding to a particular 3-digit number in a given array does not necessarily correspond to the same 3-digit number, e.g. ArrayA(1)=123=ArrayB(2).
The arrays are of arbitrary length (there could be any number of numbers in A, B, or C) but there are only three arrays.
This makes it easy to output something such as:
123 - A
234 - A
345 - B
123 - B
567 - B
123 - C
789 - C
567 - C
but this is NOT my desired result.
I need it in this format:
123 - A, B, C
234 - A
345 - B
567 - B, C
789 - C
To play with this problem directly, here's some code that generates the "easy" string:
Dim ArrayA(2), ArrayB(3), ArrayC(3) As Integer, Output As String
ArrayA(1) = 123
ArrayA(2) = 234
ArrayB(1) = 345
ArrayB(2) = 123
ArrayB(3) = 567
ArrayC(1) = 123
ArrayC(2) = 789
ArrayC(3) = 567
For i=1 to 2
Output = Output & ArrayA(i) & " - A" & vbNewLine
Next i
For i=1 to 3
Output = Output & ArrayB(i) & " - B" & vbNewLine
Next i
For i=1 to 3
Output = Output & ArrayC(i) & " - C" & vbNewLine
Next i
MsgBox(Output)
As mentioned above, I'm hoping to move the format such that it is organized by three-digit number, rather than by letter.
My best attempt at a solution would be to try to write the data into an excel sheet, sort it appropriately, and pull it back into VBA, which seems unnecessarily ugly. For example:
For i=1 to Len(ArrayA)+Len(ArrayB)+Len(ArrayC)
If i < Len(ArrayA) Then
Range("A:"&i).Value = ArrayA(i)
Range("B:"&i).Value = "A,"
End If
If i > Len(ArrayA) And i <= Len(ArrayA) + Len(ArrayB) Then
Range("A:"&i).Value = ArrayB(i)
Range("B:"&i).Value = Range("B:"&i).Value & "B,"
End If
if i >= Len(ArrayA)+Len(ArrayB) Then
Range("A:"&i).Value = ArrayC(i)
Range("B:"&i).Value = Range("B:"&i).Value & "C,"
Next i
Then I could sort this, search out duplicates, and properly combine them, and finally get to the correct output of:
123 - A, B, C
234 - A
345 - B
567 - B, C
789 - C

Answer 1

Try the following:
Sub PopulateFromArrays()
Call WriteArray(ArrayA, "A")
Call WriteArray(ArrayB, "B")
Call WriteArray(ArrayC, "C")
End Sub
Function WriteArray(MyArray, MyString)
i = 2
For j = LBound(MyArray) To UBound(MyArray)
ValueFound = False
k = ActiveSheet.Range("A" & Rows.Count).End(xlUp).Row
For i = 2 To k
If Range("A" & i).Value = MyArray(j) Then
Range("B" & i).Value = Range("B" & i).Value & ", " & MyString
ValueFound = True
Exit For
End If
Next i
If ValueFound = False Then
Range("A" & k + 1).Value = MyArray(j)
Range("B" & k + 1).Value = MyString
End If
Next j
End Function
FYI for testing I populated the arrays with the following:
ArrayA = Array(123, 456, 789)
ArrayB = Array(123, 567, 912)
ArrayC = Array(456, 789, 567)
And the result was:

Answer 2

Seems like a good use case for dictionaries:
ArrayA(1) = 123
ArrayA(2) = 234
ArrayB(1) = 345
ArrayB(2) = 123
ArrayB(3) = 567
ArrayC(1) = 123
ArrayC(2) = 789
ArrayC(3) = 567
'...
Dim e, dictArrays, dictOut, k
Set dictArrays = Createobject("scripting.dictionary")
Set dictOut = Createobject("scripting.dictionary")
dictArrays.Add "A", ArrayA
dictArrays.Add "B", ArrayB
dictArrays.Add "C", ArrayC
For Each k in dictArrays.Keys
For Each e in dictArrays(k)
If dictOut.Exists(e) then
dictOut(e) = dictOut(e) & "," & k
Else
dictOut.Add e, k
End If
Next e
Next k
'output the result
For Each k in dictOut.Keys
Debug.Print k, dictOut(k)
Next k