Imports System

Public Module Module1

 Sub Main()

​

        Dim numbersToSort(1000) As Integer

        Dim rng As Random = New Random

​

        Console.WriteLine("Quicksort Test")

                'Set up an array with 1000 random numbers between 1 and 100

        For i = 0 To numbersToSort.Length - 1

            numbersToSort(i) = rng.Next(1, 101)

        Next

​

'send array to quicksort function - will return the sorted list

        numbersToSort = quickSort(numbersToSort)

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'output the sorted list

        For i = 0 To numbersToSort.Length - 1

            Console.WriteLine(numbersToSort(i))

        Next

​

        Console.ReadLine()

​

    End Sub

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    Function quickSort(ByVal listToSort() As Integer)

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'initialise variables

        Dim pivot As Integer = listToSort.Length - 1

        Dim wall As Integer = 0

        Dim currentItem As Integer = 0

        Dim temp As Integer

​

        'If list is size one end of sort sequence

        If listToSort.Length <= 1 Then

            Return listToSort

        Else

'perform quicksort iteration

            Do Until currentItem = pivot

                If listToSort(currentItem) <= listToSort(pivot) Then

                    temp = listToSort(wall)

                    listToSort(wall) = listToSort(currentItem)

                    listToSort(currentItem) = temp

                    wall = wall + 1

                End If

                currentItem = currentItem + 1

            Loop

'swap pivot and wall - everything right of wall is now higher, left is lower

            temp = listToSort(wall)

            listToSort(wall) = listToSort(pivot)

            listToSort(pivot) = temp

​

'split into two lists (left and right) - fudge for VB

            Dim leftList(wall - 1) As Integer

            Dim rightList((listToSort.Length - 1) - wall) As Integer

            Array.Copy(listToSort, 0, leftList, 0, wall)

            Array.Copy(listToSort, wall, rightList, 0, listToSort.Length - wall)

​

            'requicksort

            leftList = quickSort(leftList)

            rightList = quickSort(rightList)

            Dim returnList((leftList.Length + rightList.Length) - 1) As Integer

            leftList.CopyTo(returnList, 0)

            rightList.CopyTo(returnList, leftList.Length)

​

            Return returnList

​

        End If

​

​

​

​

    End Function

​

End Module