Question

在不使用Array.Sort函数的情况下，我应该从两个文件中读取数字（按照从最小到最大的顺序单独排序），并将它们合并到最小到最大顺序的列表框中。我认为这是一个优雅的问题解决方案，但有一个我似乎无法消除的错误。

如果没有看到它就很难解释，所以这里是我的代码（目前没有错误处理程序）：

Private Sub btnMerge_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMerge.Click
    'read the files entered in the text boxes
    Dim file1() As String = IO.File.ReadAllLines(txtFile1.Text)
    Dim file2() As String = IO.File.ReadAllLines(txtFile2.Text)
    'simplify removal of the smallest item of the array.  
    '(the last item because the values in each file are sorted)
    Array.Reverse(file1)
    Array.Reverse(file2)

    While file1.Length > 0 Or file2.Length > 0 'as long as there are numbers left in either array
        If file1.Length And file2.Length Then 'numbers in both arrays
            Debug.WriteLine(file1.Last & " vs " & file2.Last)
            If CInt(file1.Last) < CInt(file2.Last) Then
                lstOutput.Items.Add(file1.Last)
                ReDim Preserve file1(file1.Length - 2) 'remove last (smallest) number
            Else
                lstOutput.Items.Add(file2.Last)
                ReDim Preserve file2(file2.Length - 2) 'remove last (smallest) number
            End If
        ElseIf file1.Length Then 'file2 is empty.  comparison of last values will throw an error
            Debug.WriteLine(file1.Last & " vs " & "Nothing")
            lstOutput.Items.Add(file1.Last)
            ReDim Preserve file1(file1.Length - 2) 'remove last (smallest) number
        ElseIf file2.Length Then 'file1 is empty.  comparison of last values will throw an error
            Debug.WriteLine("Nothing" & " vs " & file2.Last)
            lstOutput.Items.Add(file2.Last)
            ReDim Preserve file2(file2.Length - 2) 'remove last (smallest) number
        End If
    End While
End Sub

File1.dat：

File2.DAT的：

lstOutput中的输出是：

4
5
10
12
23
34 <-- what??
20
25
45
46
52

调试日志中的输出是：

12 vs 4

12 vs 5

12 vs 10

12 vs 20

23 vs Nothing＆lt; - what ??

34 vs Nothing＆lt; - what ??

45 vs 20

45 vs 25

45 vs Nothing

46 vs Nothing

52 vs Nothing

正如您所看到的，该算法在第五次比较和第六次比较之后表现完美。但是为什么在20之前将34插入列表框？调试日志中间的那两个“vs Nothing”来自哪里？ file2.Length评估为False - 连续两次 - 当它实际为2时（通过断点确认）！

_{注意：我完全清楚不鼓励使用ReDim Preserve。如果您有理由相信这是问题，请仅对其进行评论。}

Answer 1

你的IF不正确，就像你写的那样，它正在做一个按位操作。你应该有。

If file1.Length > 0 And file2.Length > 0 Then

就个人而言，我只会保留每个数组当前位置的索引而不是反向/重新编号。

Answer 2

我可以将其归结为几乎一行：

Private Sub btnMerge_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMerge.Click
    For Each i As Integer In IO.File.ReadLines(txtFile1.Text).Concat(IO.File.ReadLines(txtFile2.Text)).OrderBy(Function(s) Convert.ToInt32(s)).Distinct()
        lstOutput.Items.Add(i)
    Next 
End Sub

但是，它更具可读性：

Private Sub btnMerge_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMerge.Click
    Dim numbers = File.ReadLines(txtFile1.Text) _ 
         .Concat(IO.File.ReadLines(txtFile2.Text)) 
         .Select(Function(s) Convert.ToInt32(s))
         .OrderBy(Function(i) i) _
         .Distinct()

    For Each i As Integer In numbers
        lstOutput.Items.Add(i)
    Next 
End Sub

当实际为2时，Array.Length的计算结果为false？帮助组合+排序数组

2 个答案: