Question

我一直想知道是否有递归方式使我的代码在下面的功能中发挥作用。

我确实在Stack Overflow上看到了一些示例，但是它们似乎都只处理本地驱动器上的现有文件结构。

Zip文件没有文件结构。仅列出完整路径。

在我没有发布任何编码尝试之前，我不知道该怎么做。递归是巫术魔术，我从来没有能够在没有示例工作的情况下正确地进行编码。

以下是我制定的解决方案。如果有人试图解决这个问题。它可以工作，但只能处理8级嵌套。一旦了解了代码的工作原理，就可以轻松扩展它。

如果可以将其转换为更紧凑且可能更快的内容，我想尝试在一些指导下对其进行编码。

Module modZipFolderResolver
Public root As root_
Public Structure root_
    Public node() As root_
    Public name As String
    Public index As Integer
    Public isDir As Boolean
    Public count As Integer
    Dim n As TreeNode
    Public Function find(f As String, ByRef idx As Integer)
        If node Is Nothing Then
            Return False
        End If
        For k = 0 To Me.node.Length - 1
            If node(k).name = f Then
                idx = k
                Return True
            End If
        Next
        Return False
    End Function
    Public Sub add(ByRef s As String, ByRef idx As Integer, ByVal fullname As String, ByRef p_node As TreeNode, ByVal isDir As Boolean)
        ReDim Preserve Me.node(Me.count + 1)
        idx = Me.count
        node(Me.count) = New root_
        node(Me.count).name = s
        '------------------------------------
        'add node
        Dim nn As New TreeNode 'create new treevire node
        nn.Tag = fullname
        nn.Text = Me.node(Me.count).name
        If isDir Then ' set image index based on type
            Me.node(Me.count).isDir = True
            nn.SelectedImageIndex = 2
            nn.ImageIndex = 2
            nn.Name = "dir" 'used for evauation when clicked
        Else
            Me.node(Me.count).isDir = False
            nn.SelectedImageIndex = 1
            nn.ImageIndex = 0
            nn.Name = ""
        End If
        '------------------------------------
        ' make a new one if its blank
        If p_node Is Nothing Then
            p_node = New TreeNode
            p_node.Text = Me.name
        End If
        Me.node(Me.count).n = New TreeNode
        Me.node(Me.count).n = nn
        p_node.Nodes.Add(Me.node(Me.count).n)
        '------------------------------------
        Me.count += 1
    End Sub
End Structure

Public Sub build_tree()
    '--------------------------------------------------------
    'create the root node
    root = New root_
    GC.Collect() ' clean up garbage if we just killed existing data
    root.n = New TreeNode
    root.n.SelectedImageIndex = 2
    root.n.ImageIndex = 2
    root.n.Text = frmTreeList.tv_filenames.SelectedNode.Text
    root.n.Name= "dir"
    frmTreeList.tv_contents.Nodes.Add(root.n) 'Add to treeview
    '--------------------------------------------------------
    'now the fun up part. Create the nested tree structure.
    Dim indexes(9) As Integer 'used to keep track of where we are in the tree structure
    Dim isDir As Boolean = False ' flag for setting up image index
    For Each ent In current_package
        Dim ext = Path.GetExtension(ent.FileName)
        If ext.Length > 0 Then 'is this entry a file or directory?
            isDir = False
        Else
            isDir = True
        End If
        Dim a = ent.FileName.Split("/")
        For i = 0 To 8 ' 8 levels deep enough?
            If a.Length = 2 Then
                Exit For
            End If
            If i > a.Length - 1 Then
                Exit For
            End If
            For k = i To a.Length - 1
                If a(k) = "" Then
                    Exit For
                End If
                Dim idx As Integer
                Select Case k
                    Case 0
                        If root.find(a(0), idx) Then
                            indexes(0) = idx
                        Else
                            root.add(a(0), idx, ent.FileName, root.n, isDir)
                            indexes(0) = idx
                            Exit For
                        End If
                    Case 1
                        If root.node(indexes(0)).find(a(1), idx) Then
                            indexes(1) = idx
                        Else
                            Dim n = root.node(indexes(0)).n
                            root.node(indexes(0)).add(a(1), idx, ent.FileName, n, isDir)
                            indexes(1) = idx
                            Exit For
                        End If
                    Case 2
                        If root.node(indexes(0)).node(indexes(1)).find(a(2), idx) Then
                            indexes(2) = idx
                        Else
                            Dim n = root.node(indexes(0)).node(indexes(1)).n
                            root.node(indexes(0)).node(indexes(1)).add(a(2), idx, ent.FileName, n, isDir)
                            indexes(2) = idx
                            Exit For
                        End If
                    Case 3
                        If root.node(indexes(0)).node(indexes(1)).node(indexes(2)).find(a(3), idx) Then
                            indexes(3) = idx
                        Else
                            Dim n = root.node(indexes(0)).node(indexes(1)).node(indexes(2)).n
                            root.node(indexes(0)).node(indexes(1)).node(indexes(2)).add(a(3), idx, ent.FileName, n, isDir)
                            indexes(3) = idx
                            Exit For
                        End If
                    Case 4
                        If root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).find(a(4), idx) Then
                            indexes(4) = idx
                        Else
                            Dim n = root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).n
                            root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).add(a(4), idx, ent.FileName, n, isDir)
                            indexes(4) = idx
                            Exit For
                        End If
                    Case 5
                        If root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).find(a(5), idx) Then
                            indexes(5) = idx
                        Else
                            Dim n = root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).n
                            root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).add(a(5), idx, ent.FileName, n, isDir)
                            indexes(5) = idx
                            Exit For
                        End If
                    Case 6
                        If root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).find(a(6), idx) Then
                            indexes(6) = idx
                        Else
                            Dim n = root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).n
                            root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).add(a(6), idx, ent.FileName, n, isDir)
                            indexes(6) = idx
                            Exit For
                        End If
                    Case 7
                        If root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).node(indexes(6)).find(a(7), idx) Then
                            indexes(7) = idx
                        Else
                            Dim n = root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).node(indexes(6)).n
                            root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).node(indexes(6)).add(a(7), idx, ent.FileName, n, isDir)
                            indexes(7) = idx
                            Exit For
                        End If
                    Case 8
                        If root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).node(indexes(6)).node(indexes(7)).find(a(8), idx) Then
                            indexes(8) = idx
                        Else
                            Dim n = root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).node(indexes(6)).node(indexes(7)).n
                            root.node(indexes(0)).node(indexes(1)).node(indexes(2)).node(indexes(3)).node(indexes(4)).node(indexes(5)).node(indexes(6)).node(indexes(7)).add(a(8), idx, ent.FileName, n, isDir)
                            indexes(8) = idx
                            Exit For
                        End If
                End Select
            Next 'k
        Next 'i
    Next 'each ent
End Sub
End Module

此代码运行良好，并生成这样的树状视图。我只是希望有人可以阐明可能使用递归来加快速度。

Answer 1

就算法而言，我将按以下方式进行：-

对于每个路径：- 用“ /”字符将路径分成字符串数组。将此数组连同根节点和索引0一起传递到新函数中，以表明您正在使用该数组。

该功能应：- 获取传入的索引的路径组件在作为与路径组件匹配的参数传入的节点内查找或创建子节点如果传入的索引等于路径组件数组-1的长度，则返回找到/创建的子节点否则，该函数应返回对其自身的调用结果，并传入子节点和在+1中传递的索引

此函数应根据需要创建节点，并返回路径的节点

Answer 2

我发现了一个解决方案，尽管它似乎稍微慢一些。可能是因为必须通过调用堆栈返回。我将设置一个计时器，并调用旧版本和新版本，然后使用最快的版本。这不仅限于zip文件。任何文件路径列表都会生成正确构建的TreeView。

新方法的优点是，嵌套深度没有限制，除非扩展代码，否则旧版本限于8。

只是有一个主意。检查路径的拆分数组有多深，如果它的8个以上调用新版本，否则调用旧版本。

更新：我做了一些时间研究，而新版本的运行速度较慢。

不同大小的zip文件的结果

==================================
Path Count: 10756
New method: 0.328ms
Old method: 0.275ms

==================================
Path Count: 11860
New method: 0.338ms
Old method: 0.287ms

==================================
Path Count: 06672
New method: 0.189ms
Old method: 0.177ms

==================================
Path Count: 01168
New method: 0.032ms
Old method: 0.027ms

新方法代码：

Public Sub build_tree_recrusive()
    '--------------------------------------------------------
    'create the root node
    root = New root_
    GC.Collect() ' clean up garbage if we just killed existing data
    root.n = New TreeNode
    root.n.SelectedImageIndex = 2
    root.n.ImageIndex = 2
    root.n.Text = frmTreeList.tv_filenames.SelectedNode.Text
    root.n.Name = "dir"
    frmTreeList.tv_contents.Nodes.Add(root.n) 'Add to treeview
    '--------------------------------------------------------
    'now the fun up part. Create the nested tree structure.
    Dim indexes(9) As Integer 'used to keep track of where we are in the tree structure
    Dim isDir As Boolean = False ' flag for setting up image index
    For Each ent In current_package
        Dim ext = Path.GetExtension(ent.FileName)
        If ext.Length > 0 Then 'is this entry a file or directory?
            isDir = False
        Else
            isDir = True
        End If
        Dim a = ent.FileName.Split("/")

        rc(a, 0, 0, root, ent.FileName, isDir)

    Next 'each ent
End Sub
Private Function rc(ByRef a() As String, ByRef idx As Integer, ByRef ndx As Integer, ByRef node As root_, ByRef fullpath As String, ByVal isDir As Boolean) As Boolean
    If idx = a.Length Then Return True
    If a(idx) = "" Then Return True
    If node.find(a(idx), ndx) Then
        If rc(a, idx + 1, ndx, node.node(ndx), fullpath, isDir) Then
            Return True
        End If
    Else
        node.add(a(idx), ndx, fullpath, node.n, isDir)
        If rc(a, idx + 1, ndx, node.node(ndx), fullpath, isDir) Then
            Return True
        End If
    End If
    Return True
End Function

递归将ZIP文件结构转换为Treeview

2 个答案: