Les queues
Publié: 30 Jan 2005 à 12:51Merci à son auteur
- Code : Tout sélectionner
Private Class QueueNode
item As Variant
link As QueueNode
Public Sub new(inItem As Variant, inLink As QueueNode)
If Isobject(inItem) Then
Set Me.item = inItem
Else
Me.item = inItem
End If
Set Me.link = inLink
End Sub
Public Function getItem() As Variant
If Isobject(Me.item) Then
Set Me.getItem = Me.item
Else
Me.getItem = Me.item
End If
End Function
Public Function getLink() As QueueNode
Set Me.getLink = Me.link
End Function
Public Sub setLink(inLink As QueueNode)
Set Me.link = inLink
End Sub
End Class
Public Class Queue
front As QueueNode
rear As QueueNode
items As Integer
Public Sub new()
' Creates a new Queue
items = 0
End Sub
Public Function isEmpty() As Variant
' Returns true if the queue has no elements, false if not
Me.isEmpty = (items = 0)
End Function
Public Sub insert(element As Variant)
' Puts the specified element in the last position in the queue
If Isobject(element) Then If element Is Nothing _
Then Error 2000, "The value [Nothing] can not be inserted into queues"
Dim tmp As New QueueNode(element, Nothing)
If rear Is Nothing Then
Set front = tmp
Set rear = tmp
Else
Call rear.setLink(tmp)
Set rear = tmp
End If
items = items + 1
End Sub
Public Function remove() As Variant
' Returns the first element in the queue and removes it from the queue
Print "Entered remove()"
Set Me.remove = Nothing
If items = 0 Then Exit Function
Dim tmp As Variant
Print "getting front item..."
If Isobject(Me.front.getItem()) Then
Set tmp = Me.front.getItem()
Else
tmp = Me.front.getItem()
End If
Print "getting front..."
Set front = front.getLink()
If front Is Nothing Then Set rear = Nothing
items = items - 1
If Isobject(tmp) Then
Set Me.remove = tmp
Else
Me.remove = tmp
End If
End Function
Public Function getFront() As Variant
' Returns the front of the queue, without removing it from the queue
If Isobject(Me.front.getItem()) Then
Set Me.getFront = Me.front.getItem()
Else
Me.getFront = Me.front.getItem()
End If
End Function
Public Function toArray() As Variant
' Returns an array representation of this queue
Dim a As Variant
Redim a(items-1)
Dim node As QueueNode
Set node = front
Dim i As Integer
For i = 0 To items - 1
If Isobject(node.getItem()) Then
Set a(i) = node.getItem()
Else
a(i) = node.getItem()
End If
Set node = node.getLink()
Next i
Me.toArray = a
End Function
Public Function toString() As String
' Returns a String representation of this Queue
Dim i As Integer
Dim node As QueueNode
Set node = front
Dim tmp As String
If items > 2 Then
For i = 0 To items - 2
If Isobject(node.getItem()) Then
tmp = tmp & node.getItem().toString()
Else
tmp = tmp & node.getItem()
End If
tmp = tmp & ", "
Set node = node.getLink()
Next i
End If
If Isobject(node.getItem()) Then
tmp = tmp & node.getItem().toString()
Else
tmp = tmp & node.getItem()
End If
toString = tmp
End Function
End Class