VBA array sort function?

Explanation in German but the code is a well-tested in-place implementation:

Private Sub QuickSort(ByVal Field() As String, ByVal LB As Long, ByVal UB As Long)
    Dim P1 As Long, P2 As Long, Ref As String, TEMP As String

    P1 = LB
    P2 = UB
    Ref = Field((P1 + P2) / 2)

    Do
        Do While (Field(P1) < Ref)
            P1 = P1 + 1
        Loop

        Do While (Field(P2) > Ref)
            P2 = P2 - 1
        Loop

        If P1 <= P2 Then
            TEMP = Field(P1)
            Field(P1) = Field(P2)
            Field(P2) = TEMP

            P1 = P1 + 1
            P2 = P2 - 1
        End If
    Loop Until (P1 > P2)

    If LB < P2 Then Call QuickSort(Field, LB, P2)
    If P1 < UB Then Call QuickSort(Field, P1, UB)
End Sub

Invoked like this:

Call QuickSort(MyArray, LBound(MyArray), UBound(MyArray))

I converted the 'fast quick sort' algorithm to VBA, if anyone else wants it.

I have it optimized to run on an array of Int/Longs but it should be simple to convert it to one that works on arbitrary comparable elements.

Private Sub QuickSort(ByRef a() As Long, ByVal l As Long, ByVal r As Long)
    Dim M As Long, i As Long, j As Long, v As Long
    M = 4

    If ((r - l) > M) Then
        i = (r + l) / 2
        If (a(l) > a(i)) Then swap a, l, i '// Tri-Median Methode!'
        If (a(l) > a(r)) Then swap a, l, r
        If (a(i) > a(r)) Then swap a, i, r

        j = r - 1
        swap a, i, j
        i = l
        v = a(j)
        Do
            Do: i = i + 1: Loop While (a(i) < v)
            Do: j = j - 1: Loop While (a(j) > v)
            If (j < i) Then Exit Do
            swap a, i, j
        Loop
        swap a, i, r - 1
        QuickSort a, l, j
        QuickSort a, i + 1, r
    End If
End Sub

Private Sub swap(ByRef a() As Long, ByVal i As Long, ByVal j As Long)
    Dim T As Long
    T = a(i)
    a(i) = a(j)
    a(j) = T
End Sub

Private Sub InsertionSort(ByRef a(), ByVal lo0 As Long, ByVal hi0 As Long)
    Dim i As Long, j As Long, v As Long

    For i = lo0 + 1 To hi0
        v = a(i)
        j = i
        Do While j > lo0
            If Not a(j - 1) > v Then Exit Do
            a(j) = a(j - 1)
            j = j - 1
        Loop
        a(j) = v
    Next i
End Sub

Public Sub sort(ByRef a() As Long)
    QuickSort a, LBound(a), UBound(a)
    InsertionSort a, LBound(a), UBound(a)
End Sub

I posted some code in answer to a related question on StackOverflow:

Sorting a multidimensionnal array in VBA

The code samples in that thread include:

1. A vector array Quicksort;
2. A multi-column array QuickSort;
3. A BubbleSort.

Alain's optimised Quicksort is very shiny: I just did a basic split-and-recurse, but the code sample above has a 'gating' function that cuts down on redundant comparisons of duplicated values. On the other hand, I code for Excel, and there's a bit more in the way of defensive coding - be warned, you'll need it if your array contains the pernicious 'Empty()' variant, which will break your While... Wend comparison operators and trap your code in an infinite loop.

Note that quicksort algorthms - and any recursive algorithm - can fill the stack and crash Excel. If your array has less than 1024 members, I'd use a rudimentary BubbleSort.

Public Sub QuickSortArray(ByRef SortArray As Variant, _
                                Optional lngMin As Long = -1, _ 
                                Optional lngMax As Long = -1, _ 
                                Optional lngColumn As Long = 0)
On Error Resume Next

'Sort a 2-Dimensional array

' SampleUsage: sort arrData by the contents of column 3
'
'   QuickSortArray arrData, , , 3

'
'Posted by Jim Rech 10/20/98 Excel.Programming

'Modifications, Nigel Heffernan:

'       ' Escape failed comparison with empty variant
'       ' Defensive coding: check inputs

Dim i           As Long
Dim j           As Long
Dim varMid      As Variant
Dim arrRowTemp  As Variant
Dim lngColTemp  As Long

If IsEmpty(SortArray) Then
     Exit Sub
 End If

If InStr(TypeName(SortArray), "()") < 1 Then  'IsArray() is somewhat broken: Look for brackets in the type name
     Exit Sub
 End If

If lngMin = -1 Then
     lngMin = LBound(SortArray, 1)
 End If

If lngMax = -1 Then
     lngMax = UBound(SortArray, 1)
 End If

If lngMin >= lngMax Then ' no sorting required
     Exit Sub
 End If

i = lngMin
 j = lngMax

varMid = Empty
 varMid = SortArray((lngMin + lngMax) \ 2, lngColumn)

' We  send 'Empty' and invalid data items to the end of the list:
 If IsObject(varMid) Then  ' note that we don't check isObject(SortArray(n)) - varMid might pick up a valid default member or property
     i = lngMax
     j = lngMin
 ElseIf IsEmpty(varMid) Then
     i = lngMax
     j = lngMin
 ElseIf IsNull(varMid) Then
     i = lngMax
     j = lngMin
 ElseIf varMid = "" Then
     i = lngMax
     j = lngMin
 ElseIf varType(varMid) = vbError Then
     i = lngMax
     j = lngMin
 ElseIf varType(varMid) > 17 Then
     i = lngMax
     j = lngMin
 End If

While i <= j

 While SortArray(i, lngColumn) < varMid And i < lngMax
     i = i + 1
 Wend

 While varMid < SortArray(j, lngColumn) And j > lngMin
     j = j - 1
 Wend


 If i <= j Then

     ' Swap the rows
     ReDim arrRowTemp(LBound(SortArray, 2) To UBound(SortArray, 2))
     For lngColTemp = LBound(SortArray, 2) To UBound(SortArray, 2)
         arrRowTemp(lngColTemp) = SortArray(i, lngColTemp)
         SortArray(i, lngColTemp) = SortArray(j, lngColTemp)
         SortArray(j, lngColTemp) = arrRowTemp(lngColTemp)
     Next lngColTemp
     Erase arrRowTemp

     i = i + 1
     j = j - 1

 End If


Wend

If (lngMin < j) Then Call QuickSortArray(SortArray, lngMin, j, lngColumn)
 If (i < lngMax) Then Call QuickSortArray(SortArray, i, lngMax, lngColumn)

End Sub

You didn't want an Excel-based solution but since I had the same problem today and wanted to test using other Office Applications functions I wrote the function below.

Limitations:

• 2-dimensional arrays;
• maximum of 3 columns as sort keys;
• depends on Excel;

Tested calling Excel 2010 from Visio 2010

Option Base 1


Private Function sort_array_2D_excel(array_2D, array_sortkeys, Optional array_sortorders, Optional tag_header As String = "Guess", Optional tag_matchcase As String = "False")

'   Dependencies: Excel; Tools > References > Microsoft Excel [Version] Object Library

    Dim excel_application As Excel.Application
    Dim excel_workbook As Excel.Workbook
    Dim excel_worksheet As Excel.Worksheet

    Set excel_application = CreateObject("Excel.Application")

    excel_application.Visible = True
    excel_application.ScreenUpdating = False
    excel_application.WindowState = xlNormal

    Set excel_workbook = excel_application.Workbooks.Add
    excel_workbook.Activate

    Set excel_worksheet = excel_workbook.Worksheets.Add
    excel_worksheet.Activate
    excel_worksheet.Visible = xlSheetVisible

    Dim excel_range As Excel.Range
    Set excel_range = excel_worksheet.Range("A1").Resize(UBound(array_2D, 1) - LBound(array_2D, 1) + 1, UBound(array_2D, 2) - LBound(array_2D, 2) + 1)
    excel_range = array_2D


    For i_sortkey = LBound(array_sortkeys) To UBound(array_sortkeys)

        If IsNumeric(array_sortkeys(i_sortkey)) Then
            sortkey_range = Chr(array_sortkeys(i_sortkey) + 65 - 1) & "1"
            Set array_sortkeys(i_sortkey) = excel_worksheet.Range(sortkey_range)

        Else
            MsgBox "Error in sortkey parameter:" & vbLf & "array_sortkeys(" & i_sortkey & ") = " & array_sortkeys(i_sortkey) & vbLf & "Terminating..."
            End

        End If

    Next i_sortkey


    For i_sortorder = LBound(array_sortorders) To UBound(array_sortorders)
        Select Case LCase(array_sortorders(i_sortorder))
            Case "asc"
                array_sortorders(i_sortorder) = XlSortOrder.xlAscending
            Case "desc"
                array_sortorders(i_sortorder) = XlSortOrder.xlDescending
            Case Else
                array_sortorders(i_sortorder) = XlSortOrder.xlAscending
        End Select
    Next i_sortorder

    Select Case LCase(tag_header)
        Case "yes"
            tag_header = Excel.xlYes
        Case "no"
            tag_header = Excel.xlNo
        Case "guess"
            tag_header = Excel.xlGuess
        Case Else
            tag_header = Excel.xlGuess
    End Select

    Select Case LCase(tag_matchcase)
        Case "true"
            tag_matchcase = True
        Case "false"
            tag_matchcase = False
        Case Else
            tag_matchcase = False
    End Select


    Select Case (UBound(array_sortkeys) - LBound(array_sortkeys) + 1)
        Case 1
            Call excel_range.Sort(Key1:=array_sortkeys(1), Order1:=array_sortorders(1), Header:=tag_header, MatchCase:=tag_matchcase)
        Case 2
            Call excel_range.Sort(Key1:=array_sortkeys(1), Order1:=array_sortorders(1), Key2:=array_sortkeys(2), Order2:=array_sortorders(2), Header:=tag_header, MatchCase:=tag_matchcase)
        Case 3
            Call excel_range.Sort(Key1:=array_sortkeys(1), Order1:=array_sortorders(1), Key2:=array_sortkeys(2), Order2:=array_sortorders(2), Key3:=array_sortkeys(3), Order3:=array_sortorders(3), Header:=tag_header, MatchCase:=tag_matchcase)
        Case Else
            MsgBox "Error in sortkey parameter:" & vbLf & "Maximum number of sort columns is 3!" & vbLf & "Currently passed: " & (UBound(array_sortkeys) - LBound(array_sortkeys) + 1)
            End
    End Select


    For i_row = 1 To excel_range.Rows.Count

        For i_column = 1 To excel_range.Columns.Count

            array_2D(i_row, i_column) = excel_range(i_row, i_column)

        Next i_column

    Next i_row


    excel_workbook.Close False
    excel_application.Quit

    Set excel_worksheet = Nothing
    Set excel_workbook = Nothing
    Set excel_application = Nothing


    sort_array_2D_excel = array_2D


End Function

This is an example on how to test the function:

Private Sub test_sort()

    array_unsorted = dim_sort_array()

    Call msgbox_array(array_unsorted)

    array_sorted = sort_array_2D_excel(array_unsorted, Array(2, 1, 3), Array("desc", "", "asdas"), "yes", "False")

    Call msgbox_array(array_sorted)

End Sub


Private Function dim_sort_array()

    Dim array_unsorted(1 To 5, 1 To 3) As String

    i_row = 0

    i_row = i_row + 1
    array_unsorted(i_row, 1) = "Column1": array_unsorted(i_row, 2) = "Column2": array_unsorted(i_row, 3) = "Column3"

    i_row = i_row + 1
    array_unsorted(i_row, 1) = "OR": array_unsorted(i_row, 2) = "A": array_unsorted(i_row, 3) = array_unsorted(i_row, 1) & "_" & array_unsorted(i_row, 2)

    i_row = i_row + 1
    array_unsorted(i_row, 1) = "XOR": array_unsorted(i_row, 2) = "A": array_unsorted(i_row, 3) = array_unsorted(i_row, 1) & "_" & array_unsorted(i_row, 2)

    i_row = i_row + 1
    array_unsorted(i_row, 1) = "NOT": array_unsorted(i_row, 2) = "B": array_unsorted(i_row, 3) = array_unsorted(i_row, 1) & "_" & array_unsorted(i_row, 2)

    i_row = i_row + 1
    array_unsorted(i_row, 1) = "AND": array_unsorted(i_row, 2) = "A": array_unsorted(i_row, 3) = array_unsorted(i_row, 1) & "_" & array_unsorted(i_row, 2)

    dim_sort_array = array_unsorted

End Function


Sub msgbox_array(array_2D, Optional string_info As String = "2D array content:")

    msgbox_string = string_info & vbLf

    For i_row = LBound(array_2D, 1) To UBound(array_2D, 1)

        msgbox_string = msgbox_string & vbLf & i_row & vbTab

        For i_column = LBound(array_2D, 2) To UBound(array_2D, 2)

            msgbox_string = msgbox_string & array_2D(i_row, i_column) & vbTab

        Next i_column

    Next i_row

    MsgBox msgbox_string

End Sub

If anybody tests this using other versions of office please post here if there are any problems.

Thanks!

L.

Works in Word provided you taake care of the data types being used, especially if a column is mixed e.g. a partial date can become a date based on this year and also change its format such as "9/11" becomes "11-Sep-2012"!

Presetting the Excel range to the text number format seems to solve that particular problem but may screw up the sort order for purely numeric columns such as "1,2,3,4,5,6,7,8,9,10,11" being then returned as "1,10,11,2,3,4,5,6,7,8,9".

A more focussed solution would call the function with an extra array that describes the numberformat for each column in the target array.