[Year 12 SofDev] Quick Sort Code

Mon Jun 16 13:57:13 EST 2014

Hi Andrew,
            This went into an empty form, I can't remember if I wrote it a couple of years ago or garnered it from elsewhere (if it was from someone else, thanks) .
Cheers
Damien

    Sub SortMe(ByRef a() As Object, ByVal left As Integer, ByVal right As Integer)
        Dim pivot As Integer
        If right - left > 1 Then
            pivot = getpivot(a, left, right)
            pivot = partition(a, left, right, pivot)
            SortMe(a, left, pivot)
            SortMe(a, pivot + 1, right)
        End If
    End Sub

    Sub qsort(ByRef a() As Object)
        Dim i
        Dim ii
        For i = 0 To a.Length() - 1
            ii = New System.Random().Next(0, a.Length() - 1)
            If i <> ii Then
                swap(a(i), a(ii))
            End If
        Next

        SortMe(a, 0, a.Length())
    End Sub

    Function getpivot(ByRef a() As Object, ByVal left As Integer, ByVal right As Integer)
        Return New System.Random().Next(left, right - 1)
    End Function

    Function partition(ByRef a() As Object, ByVal left As Integer, ByVal right As Integer, ByRef pivot As Integer)
        Dim i
        Dim piv
        Dim store

        piv = a(pivot)

        swap(a(right - 1), a(pivot))

        store = left
        For i = left To right - 2
            If a(i) <= piv Then
                swap(a(store), a(i))
                store = store + 1
            End If
        Next
        swap(a(right - 1), a(store))

        Return store
    End Function

    Sub swap(ByRef v1, ByRef v2)
        Dim tmp
        tmp = v1
        v1 = v2
        v2 = tmp
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim MyArray() As Object = {3, 7, 4, 0, 1, 12, 32, 4, 5}
        Dim mystring As String = ""
        Dim mystring2 As String = ""
        For counter = 0 To MyArray.Length - 1
            mystring = mystring & MyArray(counter) & ", "
        Next
        MsgBox(mystring, vbOKOnly)

        qsort(MyArray)
        For counter = 0 To MyArray.Length - 1
            mystring2 = mystring2 & MyArray(counter) & ", "
        Next
        MsgBox(mystring2, vbOKOnly)

        End

    End Sub

Damien Atkinson-Buck
Head of Learning Area: Technology/Arts

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From: Anthony Sullivan [mailto:asullivan at tps.vic.edu.au]
Sent: Sunday, 15 June 2014 2:12 PM
To: sofdev at edulists.com.au
Subject: [Year 12 SofDev] Quick Sort Code

I'm trying to code the Quick Sort algorithm from the textbook (page 126) into Visual Basic - but having a few problems

If anybody has a working example of this algorithm would it be possible to ask for a copy of the code?

Anthony

Anthony Sullivan
Head of Information Technology

20 Wooralla Drive, Mt. Eliza, Vic, 3930

T: 03 9788 7796 | F: 03 9787 7646 | asullivan at tps.vic.edu.au<mailto:asullivan at tps.vic.edu.au> | www.tps.vic.edu.au<http://www.tps.vic.edu.au>

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