VBA array sort function?

Question

I\'m looking for a decent sort implementation for arrays in VBA. A Quicksort would be preferred. Or any other sort algorithm other than bubble or merge would suffice.

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Answer 1

Heapsort implementation. An O(n log(n)) (both average and worst case), in place, unstable sorting algorithm.

Use with: Call HeapSort(A), where A is a one dimensional array of variants, with Option Base 1.

Sub SiftUp(A() As Variant, I As Long)
    Dim K As Long, P As Long, S As Variant
    K = I
    While K > 1
        P = K \ 2
        If A(K) > A(P) Then
            S = A(P): A(P) = A(K): A(K) = S
            K = P
        Else
            Exit Sub
        End If
    Wend
End Sub

Sub SiftDown(A() As Variant, I As Long)
    Dim K As Long, L As Long, S As Variant
    K = 1
    Do
        L = K + K
        If L > I Then Exit Sub
        If L + 1 <= I Then
            If A(L + 1) > A(L) Then L = L + 1
        End If
        If A(K) < A(L) Then
            S = A(K): A(K) = A(L): A(L) = S
            K = L
        Else
            Exit Sub
        End If
    Loop
End Sub

Sub HeapSort(A() As Variant)
    Dim N As Long, I As Long, S As Variant
    N = UBound(A)
    For I = 2 To N
        Call SiftUp(A, I)
    Next I
    For I = N To 2 Step -1
        S = A(I): A(I) = A(1): A(1) = S
        Call SiftDown(A, I - 1)
    Next
End Sub