Question

此程序假设按姓氏（aryTemp和aryTemp2中的索引1）按升序对记录（在arySort中）进行排序，并将结果放在旧的预加载未分类记录的列表框中。

它奇怪地排序它们，我必须多次单击Ascending按钮以获得我想从点击按钮获得的实际排序结果。

为什么不用单击鼠标对项目进行排序？

来源：

Public Class Form1
    Dim FILE_NAME As String = "Students.txt"
    Dim numberOfRecords As Integer 'total number of records
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If System.IO.File.Exists(FILE_NAME) = True Then
            Dim objReader As New System.IO.StreamReader(FILE_NAME)
            Do While objReader.Peek() <> -1
                lstBox.Items.Add(objReader.ReadLine)
                numberOfRecords += 1
            Loop
            objReader.Close()
        End If
    End Sub

    Private Sub btnAscending_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAscending.Click
        'load all students into array
        Dim arySort(numberOfRecords - 1) As String
        Dim aryTemp() As String 'holds first record's last name
        Dim aryTemp2() As String 'holds second record's last name
        For i = 0 To numberOfRecords - 1
            arySort(i) = lstBox.Items(i)
        Next
        Dim temp As String 'holds temporary record
        Dim k As Integer
        For i = 0 To arySort.Length - 2
            aryTemp = Split(arySort(i), " ")
            For k = i + 1 To arySort.Length - 1
                aryTemp2 = Split(arySort(k), " ")
                If aryTemp(1) < aryTemp2(1) Then
                    temp = arySort(k)
                    arySort(k) = arySort(i)
                    arySort(i) = temp
                End If
            Next
        Next
        lstBox.Items.Clear()
        numberOfRecords = 0
        For i = 0 To arySort.Length - 1
            lstBox.Items.Add(arySort(i))
            numberOfRecords += 1
        Next
    End Sub
End Class

Answer 1

如果您只需要对列表进行排序（正如您在评论中所说的那样），不实现您自己的排序机制，而是使用.NET：

' Define how we want to compare items '
Function compareByLastName(ByVal item1 As String, ByVal item2 As String) As Integer
    Return String.Compare(item1.Split(" ")(1), item2.Split(" ")(1))
End Function

Private Sub btnAscending_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAscending.Click
    ' load all students into array '
    Dim arySort(numberOfRecords - 1) As String
    For i = 0 To numberOfRecords - 1
        arySort(i) = lstBox.Items(i)
    Next

    ' Use built-in .NET magic '
    Array.Sort(arySort, AddressOf compareByLastName)

    ' Write the values back into your list box '
    lstBox.Items.Clear()
    numberOfRecords = 0
    For i = 0 To arySort.Length - 1
        lstBox.Items.Add(arySort(i))
        numberOfRecords += 1
    Next
End Sub

这使用.NET类库的内置快速排序算法。以下是我们使用的方法的文档：Array.Sort(T(), Comparison(Of T))。

Answer 2

与我的工作冒泡分类比较：

Public Sub BubbleSort(ByVal arr() As Integer)
    Dim flag As Boolean = False
    For i As Integer = 0 To arr.Length - 1
        For j As Integer = 0 To arr.Length - 2 - i
            If arr(j + 1) < arr(j) Then
                flag = True
                Dim temp As Integer = arr(j)
                arr(j) = arr(j + 1)
                arr(j + 1) = temp
            End If
        Next
        If flag = False Then Return ' no swaps =>already sorted
    Next
End Sub

Answer 3

我发现您的算法存在两个主要问题：

这不是冒泡排序。 Bubble sort交换相邻的元素，即它与i + 1交换i。另一方面，你用第一个j＆gt;交换一些元素i。我姓名（i）＆lt;名字（J）。也许您应该以伪代码向我们展示您实际尝试实施的算法？
aryTemp包含元素i，aryTemp2包含一些元素j＆gt;一世。如果aryTemp(1) < aryTemp2(1)，为什么要交换元素？如果您希望元素按升序排序，那么这不是正确的顺序吗？

冒泡排序逻辑错误VB.NET

3 个答案: