vb点虐 递归函数 net 递归
编写递归函数，函数只有一个参数（整数类型）比如参数=10，那么靠自己调用自己，将10到1进行累加，并返回
int nestAdd(int n) {
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if (n 1) return n + nestAdd(n - 1);
else return n;
}
有没有朋友可以详细解释一下关于VB.NET里面的递归?最好有代码加注释,谢谢.
给你个例子希望可以帮到你
递归系统目录结构.
递归整个C盘目录:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim iDir As IO.Directory
Dim node As New TreeNode
'先把C盘添加到树中
TreeView1.Nodes.Clear()
node.ImageIndex = 0
node.Text = "本地磁盘 C:"
node.SelectedImageIndex = -1
TreeView1.Nodes.Add(node)
Dim i As Integer
'获取C:盘根目录下的文件夹
Dim str() As String = IO.Directory.GetDirectories("D:\")
For i = 0 To str.GetUpperBound(0)
'调用遍历过程
AddDirectory("C:", str(i), node)
Next
node = Nothing
iDir = Nothing
End Sub
Public Sub AddDirectory(ByVal strFatherPath As String, ByVal strPath As String, ByVal nodeFather As TreeNode)
Dim iDir As IO.Directory
'Dim iDirInfo As IO.DirectoryInfo
Dim i As Integer
Dim node As New TreeNode
'先添加本目录，从文件夹路径分析出文件夹名称
node.Text = Strings.Replace(strPath, strFatherPath "\", "", , 1)
'为单个节点指定节点未被选中时显示的图标
node.ImageIndex = 1
'为单个节点指定节点被选中时显示的图标
node.SelectedImageIndex = 2
nodeFather.Nodes.Add(node)
Application.DoEvents()
Try
Dim str() As String = IO.Directory.GetDirectories(strPath)
'遍历该目录的子文件夹
For i = 0 To str.GetUpperBound(0)
AddDirectory(strPath, str(i), node)
Next
Catch ex As Exception
Debug.WriteLine(ex.Message)
End Try
node = Nothing
iDir = Nothing
End Sub
vb点虐 控件treeview从数据库获得数据分层显示
说实话一般不是你这样存储的，一般是用一个字段存储ID号，然后用另一个字段存储上级单位的ID号，然后用递归函数生成TreeView。建议你增加一个字段，然后将编号解析出的上级单位存储在里面。以下是我的一个程序用的递归函数：
表名是unit，其中包含了单位名称unit_name,编号unit_id,Unit_upper就是上级单位的id号。
调用方式是 addtree(ds1, TreeView1.Nodes, 0)，其中ds1是一个DataSet，对应单位的表，treeview1是控件名称，0是固定值，与表中根节点部门的Unit_upper一致(这个单位没有上级)。
Public Function addtree(ByVal ds As DataSet, ByVal treename As TreeNodeCollection, ByVal x1 As Integer) As Boolean
Dim dt As DataTable = ds.Tables("unit")
Dim dm As BindingManagerBase = Me.BindingContext(ds, "unit")
Dim dr As DataRow() = dt.Select("unit_upper=" x1.ToString)
Dim dr1 As DataRow
Dim nd As TreeNode
Dim nd1 As TreeNode
Dim x2 As Integer
If dr.GetLength(0) 0 Then
For Each dr1 In dr
nd = treename.Add(dr1("unit_name"))
nd.Tag = (dr1("unit_id"))
x2 = treename.IndexOf(nd)
addtree(ds, treename.Item(x2).Nodes, dr1("unit_id"))
Next
End If
Return True
End Function
vb点虐 递归 vb点虐 递归
这种不要用递归,知道关键字长度,知道节数用判断就可以了,取前3位第一节,第二节取3个为父节点,取全部为第二节关键字,第三节取前6个为父节点,取全部为第三节关键字.
并没有要求培养字段，查询时从len(ID)=3*N，每次循环时N都+1
select * from tablename where len(id)=3
select case N
case 1
treeview.node.add id,name
case 2
treeview.node(left(id,3)).node.add id,name
case 3
treeview.node(left(id,3)).node(left(id,6)).add id,name
end select
查询结果排个升序就不会存在这样的问题了,你刚才说的那种,如果中间没有比001001001001001更短的关键字,那么就脱节,这种是不可能添加到treeview中.
递归一般用在不知道节数,没有关键字的情况,比如系统目录结构.
递归整个C盘目录:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim iDir As IO.Directory
Dim node As New TreeNode
'先把C盘添加到树中
TreeView1.Nodes.Clear()
node.ImageIndex = 0
node.Text = "本地磁盘 C:"
node.SelectedImageIndex = -1
TreeView1.Nodes.Add(node)
Dim i As Integer
'获取C:盘根目录下的文件夹
Dim str() As String = IO.Directory.GetDirectories("D:\")
For i = 0 To str.GetUpperBound(0)
'调用遍历过程
AddDirectory("C:", str(i), node)
Next
node = Nothing
iDir = Nothing
End Sub
Public Sub AddDirectory(ByVal strFatherPath As String, ByVal strPath As String, ByVal nodeFather As TreeNode)
Dim iDir As IO.Directory
'Dim iDirInfo As IO.DirectoryInfo
Dim i As Integer
Dim node As New TreeNode
'先添加本目录，从文件夹路径分析出文件夹名称
node.Text = Strings.Replace(strPath, strFatherPath "\", "", , 1)
'为单个节点指定节点未被选中时显示的图标
node.ImageIndex = 1
'为单个节点指定节点被选中时显示的图标
node.SelectedImageIndex = 2
nodeFather.Nodes.Add(node)
Application.DoEvents()
Try
Dim str() As String = IO.Directory.GetDirectories(strPath)
'遍历该目录的子文件夹
For i = 0 To str.GetUpperBound(0)
AddDirectory(strPath, str(i), node)
Next
Catch ex As Exception
Debug.WriteLine(ex.Message)
End Try
node = Nothing
iDir = Nothing
End Sub
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