115 lines
3.9 KiB
VB.net
115 lines
3.9 KiB
VB.net
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Namespace ComponentModel.Algorithm.BinaryTree
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Public Class Iterator(Of K, V)
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Public _tree As RBTree(Of K, V)
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Public _ancestors As Stack(Of RBNode(Of K, V))
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Public _cursor As RBNode(Of K, V)
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Public ReadOnly Property data() As V
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Get
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Return If(Me._cursor IsNot Nothing, Me._cursor.Value, Nothing)
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End Get
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End Property
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Default Public ReadOnly Property GetDirectionValue(dir As String) As Func(Of V)
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Get
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Select Case dir
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Case NameOf(prev)
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Return AddressOf prev
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Case NameOf([next])
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Return AddressOf [next]
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Case Else
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Throw New NotImplementedException
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End Select
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End Get
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End Property
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Public Sub New(tree As RBTree(Of K, V))
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Me._tree = tree
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Me._ancestors = New Stack(Of RBNode(Of K, V))
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Me._cursor = Nothing
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End Sub
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''' <summary>
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''' if null-iterator, returns first node
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''' otherwise, returns next node
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''' </summary>
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''' <returns></returns>
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Public Function [next]() As V
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If Me._cursor Is Nothing Then
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Dim root = Me._tree.root
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If root IsNot Nothing Then
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Me._minNode(root)
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End If
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Else
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If Me._cursor.Right Is Nothing Then
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' no greater node in subtree, go up to parent
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' if coming from a right child, continue up the stack
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Dim save
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Do
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save = Me._cursor
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If Me._ancestors.Count > 0 Then
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Me._cursor = Me._ancestors.Pop()
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Else
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Me._cursor = Nothing
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Exit Do
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End If
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Loop While Me._cursor.Right = save
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Else
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' get the next node from the subtree
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Me._ancestors.Push(Me._cursor)
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Me._minNode(Me._cursor.Right)
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End If
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End If
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Return If(Me._cursor IsNot Nothing, Me._cursor.Value, Nothing)
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End Function
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''' <summary>
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''' if null-iterator, returns last node
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''' otherwise, returns previous node
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''' </summary>
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''' <returns></returns>
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Public Function prev() As V
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If Me._cursor Is Nothing Then
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Dim root = Me._tree.root
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If root IsNot Nothing Then
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Me._maxNode(root)
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End If
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Else
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If Me._cursor.Left Is Nothing Then
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Dim save
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Do
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save = Me._cursor
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If Me._ancestors.Count > 0 Then
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Me._cursor = Me._ancestors.Pop()
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Else
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Me._cursor = Nothing
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Exit Do
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End If
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Loop While Me._cursor.Left = save
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Else
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Me._ancestors.Push(Me._cursor)
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Me._maxNode(Me._cursor.Left)
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End If
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End If
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Return If(Me._cursor IsNot Nothing, Me._cursor.Value, Nothing)
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End Function
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Public Sub _minNode(start As RBNode(Of K, V))
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While start.Left IsNot Nothing
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Me._ancestors.Push(start)
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start = start.Left
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End While
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Me._cursor = start
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End Sub
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Public Sub _maxNode(start As RBNode(Of K, V))
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While start.Right IsNot Nothing
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Me._ancestors.Push(start)
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start = start.Right
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End While
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Me._cursor = start
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End Sub
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End Class
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End Namespace
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