'Visual Basic 2010 Recursie Procedures en Functies
Module QuickSort
    Sub Main()
        Dim numbers As Integer() = {88, 75, 93, 81, 21, 74, 84, 35}
        PrintArray(numbers)
        '
        QuickSort(numbers, 0, 7)
        PrintArray(numbers)
        '
        Console.ReadLine()
    End Sub
    Sub PrintArray(ByVal values As Integer())
        For Each value As Integer In values
            Console.Write(value & " ")
        Next
        Console.WriteLine()
    End Sub
    Sub QuickSort(ByVal array As Integer(), _
                  ByVal lowerbound As Integer, ByVal upperbound As Integer)
        Dim count As Integer = upperbound - lowerbound + 1
        If count = 2 Then
            If array(lowerbound) > array(upperbound) Then
                Dim backup As Integer = array(lowerbound)
                array(lowerbound) = array(upperbound)
                array(upperbound) = backup
            End If
        ElseIf count > 2 Then
            Dim pivotIndex As Integer = (lowerbound + upperbound) \ 2
            Dim pivot As Integer = array(pivotIndex)
            '
            array(pivotIndex) = array(upperbound)
            array(upperbound) = pivot
            '
            Dim smallerIndex As Integer = lowerbound
            Dim biggerIndex As Integer = upperbound
            '
            Do While smallerIndex <> biggerIndex
                '
                Do While array(smallerIndex) <= pivot AndAlso _
                         smallerIndex < biggerIndex
                    smallerIndex += 1
                Loop
                '
                Do While array(biggerIndex) >= pivot AndAlso _
                         smallerIndex < biggerIndex
                    biggerIndex -= 1
                Loop
                '
                If smallerIndex <> biggerIndex Then
                    Dim backup As Integer = array(smallerIndex)
                    array(smallerIndex) = array(biggerIndex)
                    array(biggerIndex) = backup
                End If
            Loop
            '
            array(upperbound) = array(biggerIndex)
            array(biggerIndex) = pivot
            '
            QuickSort(array, lowerbound, biggerIndex - 1)
            QuickSort(array, smallerIndex + 1, upperbound)
        End If
    End Sub
End Module
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