如何解决按字母顺序对目录路径进行排序
下面的代码用于在vb.net中对目录进行排序。
Dim a As New List(Of String)
a.Add("a\b\c")
a.Add("a\b\c\d")
a.Add("a\b\c d")
a.Add("a\b\c d\e")
a.Add("a\b\c\d\f")
a.Sort(Function(x,Y) (x).CompareTo((Y)))
结果:
a\b\c
a\b\c d
a\b\c d\e
a\b\c\d
a\b\c\d\f
在结果列表中,带有空格的目录位于“ \”之前。
有超过1500000个子目录和文件 排序大约需要50秒(默认方法) 我们尝试的所有其他方法都至少需要400秒。
如何按字母顺序对目录路径进行排序? 有没有内置的方法可以在空格前考虑反斜杠?
解决方法
您需要将路径分解为单独的文件夹名称,然后依次比较每个文件夹名称,直到发现差异为止。如果没有差异,则可以使用长度来区分,即,更高级别的文件夹位于第一位。
a.Sort(Function(x,y)
Dim xFolderNames As New List(Of String)
Dim yFolderNames As New List(Of String)
'Split first path into folder names.
Do Until String.IsNullOrEmpty(x)
xFolderNames.Insert(0,Path.GetFileName(x))
x = Path.GetDirectoryName(x)
Loop
'Split second path into folder names.
Do Until String.IsNullOrEmpty(y)
yFolderNames.Insert(0,Path.GetFileName(y))
y = Path.GetDirectoryName(y)
Loop
Dim result = 0
'Compare up to as many folders as are in the shortest path.
For i = 0 To Math.Min(xFolderNames.Count,yFolderNames.Count) - 1
result = xFolderNames(i).CompareTo(yFolderNames(i))
If result <> 0 Then
'A difference has been found.
Exit For
End If
Next
If result = 0 Then
'No difference was found so put the shortest path first.
result = xFolderNames.Count.CompareTo(yFolderNames.Count)
End If
Return result
End Function)
为了很好地衡量,这是一个封装该功能的类:
Imports System.Collections.ObjectModel
Imports System.IO
Public Class FileSystemPath
Implements IComparable,IComparable(Of FileSystemPath)
Public ReadOnly Property FullPath As String
Public ReadOnly Property PartialPaths As ReadOnlyCollection(Of String)
Public Sub New(fileOrFolderPath As String)
FullPath = fileOrFolderPath
Dim partialPaths As New List(Of String)
Do Until String.IsNullOrEmpty(fileOrFolderPath)
partialPaths.Insert(0,Path.GetFileName(fileOrFolderPath))
fileOrFolderPath = Path.GetDirectoryName(fileOrFolderPath)
Loop
Me.PartialPaths = New ReadOnlyCollection(Of String)(partialPaths)
End Sub
Public Function CompareTo(obj As Object) As Integer Implements IComparable.CompareTo
Return CompareTo(DirectCast(obj,FileSystemPath))
End Function
Public Function CompareTo(other As FileSystemPath) As Integer Implements IComparable(Of FileSystemPath).CompareTo
Dim result = 0
'Compare up to as many folders as are in the shortest path.
For i = 0 To Math.Min(PartialPaths.Count,other.PartialPaths.Count) - 1
result = PartialPaths(i).CompareTo(other.PartialPaths(i))
If result <> 0 Then
'A difference has been found.
Exit For
End If
Next
If result = 0 Then
'No difference was found so put the shortest path first.
result = PartialPaths.Count.CompareTo(other.PartialPaths.Count)
End If
Return result
End Function
Public Overrides Function ToString() As String
Return FullPath
End Function
End Class
只需更改一下代码就可以使用它:
Dim a As New List(Of FileSystemPath)
a.Add(New FileSystemPath("a\b\c"))
a.Add(New FileSystemPath("a\b\c\d"))
a.Add(New FileSystemPath("a\b\c d"))
a.Add(New FileSystemPath("a\b\c d\e"))
a.Add(New FileSystemPath("a\b\c\d\f"))
a.Sort()
Console.WriteLine(String.Join(Environment.NewLine,a))
Console.ReadLine()
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