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Sort: routine di riordinamento in VB .Net

Talvolta mi è capitato di dovere riordinare un insieme di dati, e nonostante vi siano degli strumenti adatti allo scopo, mi sono incuriosito per capire quali algoritmi si celano dietro queste routine.
Riguardando alcuni vecchi manuali di programmazione ne ho trovate qualcune, le ho "tradotte" in VB.Net, e le ho riunite in un'unica applicazione che allego di seguito:

Public Class Form1

    Private WithEvents TextBox1 As New TextBox
    Private WithEvents btnBubbleSort As New Button
    Private WithEvents btnShellSort As New Button
    Private WithEvents btnMetznerSort As New Button
    Private WithEvents btnQuickSort As New Button
    Private WithEvents btnEsci As New Button

    Dim n As Integer = 9
    Dim numero(0 To n) As Integer
    Dim elenco(0 To n) As Integer

    Public Sub New()

        InitializeComponent()

        With Me
            .Size = New Size(270, 270)
            .Text = "Metodi di riordinamento"
        End With

        With TextBox1
            .Location = New Point(12, 16)
            .Multiline = True
            .Size = New Size(114, 204)
            .ScrollBars = ScrollBars.Vertical
        End With

        With btnBubbleSort
            .Location = New Point(142, 12)
            .Size = New Size(108, 36)
            .Text = "Bubble Sort"
        End With

        With btnShellSort
            .Location = New Point(142, 54)
            .Size = New Size(108, 36)
            .Text = "Shell Sort"
        End With

        With btnMetznerSort
            .Location = New Point(142, 96)
            .Size = New Size(108, 36)
            .Text = "Metzner Shell Sort"
        End With

        With btnQuickSort
            .Location = New Point(142, 138)
            .Size = New Size(108, 36)
            .Text = "Quick Sort"
        End With

        With btnEsci
            .Location = New Point(142, 180)
            .Size = New Size(108, 36)
            .Text = "Esci"
        End With

        Me.Controls.Add(TextBox1)
        Me.Controls.Add(btnBubbleSort)
        Me.Controls.Add(btnShellSort)
        Me.Controls.Add(btnMetznerSort)
        Me.Controls.Add(btnQuickSort)
        Me.Controls.Add(btnEsci)

        Randomize()

        For i As Integer = 0 To n
            numero(i) = CInt(Int((100 * Rnd()) + 1))
            elenco(i) = numero(i)
        Next

    End Sub

    Private Sub BubbleSort(ByVal array() As Integer)

        Dim z As Boolean
        Dim num As Integer = 0

        Do
            z = False
            For i As Integer = 0 To n - 1
                If array(i) > array(i + 1) Then
                    num = array(i)
                    array(i) = array(i + 1)
                    array(i + 1) = num
                    z = True
                End If
            Next

        Loop While z = True

        Visualizza(array)

    End Sub

    Private Sub ShellSort(ByVal array() As Integer)

        Dim z As Integer = n
        Dim y As Integer
        Dim zz As Integer
        Dim xx As Integer
        Dim w As Integer

        Do
            z = CType(z / 2, Integer)
            y = n - z

            Do
                zz = 0

                For x As Integer = 0 To y
                    xx = x + z
                    If array(x) > array(xx) Then
                        w = array(x)
                        array(x) = array(xx)
                        array(xx) = w
                        zz = 1
                    End If
                Next
            Loop While zz > 0
        Loop While z > 1

        Visualizza(array)

    End Sub

    Private Sub MetznerSort(ByVal array() As Integer)

        Dim z As Integer = n
        Dim y As Integer = 0
        Dim zz As Integer = 0
        Dim x As Integer = 0
        Dim xx As Integer = 0
        Dim w As Integer = 0

        Do
            z = CType(z / 2, Integer)
            If z = 0 Then Exit Do

            y = n - z
            zz = 0

            Do
                x = zz
                Do
                    xx = x + z

                    If array(x) <= array(xx) Then
                        Exit Do
                    Else
                        w = array(x)
                        array(x) = array(xx)
                        array(xx) = w
                        x = x - z
                    End If

                Loop While x >= 1

                zz += 1

            Loop While zz <= y


        Loop While z > 0

        Visualizza(array)

    End Sub

    Private Sub QuickSort(ByVal array() As Integer)
        Dim k As Integer = 1
        Dim i As Integer = 0
        Dim s(n) As Integer
        Dim a As Integer
        Dim b As Integer
        Dim l As Integer
        Dim u As Integer
        Dim z As Integer

        s(i) = 0
        s(i + 1) = n

        Do
            If k = 0 Then Exit Do
            k -= 1
            i = k + k
            a = s(i)
            b = s(i + 1)
            z = array(a)
            u = a
            l = b + 1

            Do
                l -= 1

                If z > array(l) Then

                    array(u) = array(l)

                    Do
                        u += 1

                        If z < array(u) Then
                            array(l) = array(u)
                            Exit Do
                        End If

                    Loop While l <> u
                End If

            Loop While l <> u

            array(u) = z

            If (b - u) >= 2 Then
                i = k + k
                s(i) = u + 1
                s(i + 1) = b
                k += 1
            End If

            If l - a >= 2 Then
                i = k + k
                s(i) = a
                s(i + 1) = l - 1
                k += 1
            End If

        Loop
        Visualizza(array)

    End Sub

    Private Sub btnBubbleSort_Click(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles btnBubbleSort.Click

        Ricopia()
        TextBox1.Text += Environment.NewLine + "Bubble Sort" + Environment.NewLine
        BubbleSort(numero)

    End Sub

    Private Sub btnShellSort_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnShellSort.Click

        Ricopia()
        TextBox1.Text += Environment.NewLine + "Shell Sort" + Environment.NewLine
        ShellSort(numero)

    End Sub

    Private Sub btnMetznerSort_Click(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles btnMetznerSort.Click

        Ricopia()
        TextBox1.Text += Environment.NewLine + "Metzner Shell Sort" + Environment.NewLine
        MetznerSort(numero)

    End Sub

    Private Sub btnQuickSort_Click1(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles btnQuickSort.Click

        Ricopia()
        TextBox1.Text += Environment.NewLine + "Quick Sort" + Environment.NewLine
        QuickSort(numero)

    End Sub

    Private Sub Visualizza(ByVal array() As Integer)

        For i As Integer = 0 To n

            TextBox1.Text += elenco(i).ToString + "    " + array(i).ToString + Environment.NewLine

        Next

    End Sub

    Private Sub Ricopia()

        For i As Integer = 0 To n
            numero(i) = elenco(i)
        Next

    End Sub

    Private Sub btnEsci_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnEsci.Click

        End

    End Sub

End Class

Si tratta di 4 routine BubbleSort, ShellSort, MetznerShellSort e QuickSort.
Solamente la prima delle 4, BubbleSort, non è indicata per grandi liste, perché lenta, le altre, invece, consentono un riordinamento piuttosto veloce degli elementi. Fra tutte spicca la QuickSort.

Download sorgente "Riordinamento.zip" ( 70KB )

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Sito realizzato da Fiaschi Francesco - Aggiornamento Dicembre 2018

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