Sorting algorithms (sort array)

[Ellis Dee]

While it's no doubt been covered many times before, I was hoping to set up a nice repository of the various sorting algorithms in a single thread. So if you have VB6 code for a technique that isn't listed, please post it.

To keep the code as simple as possible, assume we are sorting single-dimension typed arrays. Your code can work for string or numeric arrays; it will be up to the reader to make any necessary conversions.

I'll start us off with the old standby, the QuickSort:

' Omit plngLeft & plngRight; they are used internally during recursion
Public Sub QuickSortLong(ByRef plngArray() As Long, Optional ByVal plngLeft As Long, Optional ByVal plngRight As Long)
    Dim lngFirst As Long
    Dim lngMid As Long
    Dim lngLast As Long
    Dim lngSwap As Long
    
    If plngRight = 0 Then
        plngLeft = LBound(plngArray)
        plngRight = UBound(plngArray)
    End If
    lngFirst = plngLeft
    lngLast = plngRight
    lngMid = plngArray((plngLeft + plngRight) \ 2)
    Do
        Do While plngArray(lngFirst) < lngMid And lngFirst < plngRight
            lngFirst = lngFirst + 1
        Loop
        Do While lngMid < plngArray(lngLast) And lngLast > plngLeft
            lngLast = lngLast - 1
        Loop
        If lngFirst <= lngLast Then
            lngSwap = plngArray(lngFirst)
            plngArray(lngFirst) = plngArray(lngLast)
            plngArray(lngLast) = lngSwap
            lngFirst = lngFirst + 1
            lngLast = lngLast - 1
        End If
    Loop Until lngFirst > lngLast
    If plngLeft < lngLast Then QuickSortLong plngArray, plngLeft, lngLast
    If lngFirst < plngRight Then QuickSortLong plngArray, lngFirst, plngRight
End Sub