Question

Public Class Form1

Private Sub GenerateAndSearch(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGenerate.Click, btnSearch.Click
    Static intDataArray(-1) As Integer
    Dim btnButtonClicked As Button = sender

    Select Case btnButtonClicked.Tag
        Case "Generate Array"
            Call GenerateSortedArray(intDataArray)

            Me.lstListArrayElements.Items.Clear()
            Call DisplayData(intDataArray, Me.lstListArrayElements, "Sorted array:")

        Case "Search Array"
            Dim intNumToFind As Integer = Val(Me.txtNumToFind.Text)
            Dim intNumFoundIndex As Integer

            intNumFoundIndex = BinarySearch(intDataArray, intNumToFind)
            If intNumFoundIndex = -1 Then
                Me.lblFoundMessage.Text = "Number not found."
            Else
                Me.lblFoundMessage.Text = "Number found at index" & intNumFoundIndex
            End If
    End Select
End Sub

Sub GenerateSortedArray(ByRef intArray() As Integer)
    Const intNUMELEMENTS As Integer = 50
    Const intMAXNUMBER As Integer = 100
    ReDim intArray(intNumElements - 1)

    Randomize()
    Dim intIndex As Integer
    For intIndex = 0 To intArray.Length - 1
        intArray(intIndex) = Int(intMAXNUMBER * Rnd()) + 1
    Next intIndex
    Call InsertionSort(intArray)
End Sub

Sub InsertionSort(ByRef intArray() As Integer)
    Dim intIndex, intPreviousIndex, intTempItem As Integer

    For intIndex = 1 To intArray.Length - 1
        intTempItem = intArray(intIndex)
        intPreviousIndex = intIndex - 1

        Do While intPreviousIndex > 0 And
            intArray(intPreviousIndex) > intTempItem
            intArray(intPreviousIndex + 1) = intArray(intPreviousIndex)
            intPreviousIndex = intPreviousIndex - 1
        Loop

        If intArray(intPreviousIndex) > intTempItem Then
            intArray(intPreviousIndex + 1) = intArray(intPreviousIndex)
            intArray(intPreviousIndex) = intTempItem
        Else
            intArray(intPreviousIndex + 1) = intTempItem
        End If
    Next intIndex
End Sub
Sub DisplayData(ByRef intArray() As Integer, ByRef lstList As ListBox, ByVal strTitle As String)
    lstList.Items.Add(strTitle)
    Dim intIndex As Integer
    For intIndex = 0 To intArray.Length - 1
        lstList.Items.Add(intIndex & vbTab & intArray(intIndex))
    Next intIndex
End Sub

Function BinarySearch(ByRef intArray() As Integer, ByVal intNumToFind As Integer) As Integer
    Dim intHighIndex As Integer = intArray.Length - 1
    Dim intMidIndex As Integer
    Dim intLowIndex As Integer = 0
    Dim blnFound As Boolean = False

    Do While (Not blnFound) And (intLowIndex <= intHighIndex)
        intMidIndex = (intMidIndex + intLowIndex) / 2
        If intArray(intMidIndex) = intNumToFind Then
            blnFound = True
        ElseIf intArray(intMidIndex) > intNumToFind Then
            intHighIndex = intMidIndex - 1
        Else
            intLowIndex = intMidIndex + 1
        End If
    Loop
    If blnFound Then
        Return intMidIndex
    Else
        Return -1
    End If
End Function
Private Sub NewData_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtNumtoFind.TextChanged, btnGenerate.Click
    Me.lblFoundMessage.text = Nothing
End Sub
End Class

我的问题是我无法让我的代码显示要查找的数组列表。我不知道我哪里出错任何想法？此外，我的排序按钮不起作用，但可能是因为当我点击按钮btnGenerate时没有显示任何内容。

Answer 1

NewData_TextChanged方法会删除搜索结果：

Me.lblFoundMessage.text = Nothing

删除该行代码并显示结果。

Answer 2

您最大的问题似乎出现在BinarySearch功能中。你没有得到任何显示的原因是BinarySearch函数有一个无限循环。这是一些带有解释的更正代码，经过测试和运行：

Function BinarySearch(ByRef intArray() As Integer, ByVal intNumToFind As Integer) As Integer
    Dim intHighIndex As Integer = intArray.Length - 1
    Dim intMidIndex As Integer
    Dim intLowIndex As Integer = 0
    Dim blnFound As Boolean = False

    Do While (Not blnFound) And (intLowIndex <= intHighIndex)
        'This should add high and low then divide by 2 not mid and low
        'Also you should use the integer division sign to return an integer result
        intMidIndex = (intHighIndex + intLowIndex) \ 2
        If intArray(intMidIndex) = intNumToFind Then
            blnFound = True
            'mid should become the new limit without any inc/decrement
        ElseIf intArray(intMidIndex) > intNumToFind Then
            intHighIndex = intMidIndex
        Else
            intLowIndex = intMidIndex
        End If
    Loop
    If blnFound Then
        Return intMidIndex
    Else
        Return -1
    End If
End Function

应该做出的其他一些更正：

Select Case btnButtonClicked.Tag应为Select Case btnButtonClicked.Tag.ToString()

intArray(intIndex) = Int(intMAXNUMBER * Rnd()) + 1应为intArray(intIndex) = CInt(intMAXNUMBER * Rnd()) + 1

另外一个想法，您可能想要检查生成例程以仅生成唯一数字。二进制搜索只会找到一个元素，但如果有更多元素，则不会找到任何其他元素。

代码很干净但在运行时它不会显示

2 个答案: