VBA Linked List


Example

This linked list example implements Set abstract data type operations.

SinglyLinkedNode class

Option Explicit

Private Value As Variant
Private NextNode As SinglyLinkedNode '"Next" is a keyword in VBA and therefore is not a valid variable name

LinkedList class

Option Explicit

Private head As SinglyLinkedNode

'Set type operations

Public Sub Add(value As Variant)
    Dim node As SinglyLinkedNode
        
    Set node = New SinglyLinkedNode
    node.value = value
    Set node.nextNode = head
    
    Set head = node
End Sub

Public Sub Remove(value As Variant)
    Dim node As SinglyLinkedNode
    Dim prev As SinglyLinkedNode
    
    Set node = head
    
    While Not node Is Nothing
        If node.value = value Then
            'remove node
            If node Is head Then
                Set head = node.nextNode
            Else
                Set prev.nextNode = node.nextNode
            End If
            Exit Sub
        End If
        Set prev = node
        Set node = node.nextNode
    Wend

End Sub

Public Function Exists(value As Variant) As Boolean
    Dim node As SinglyLinkedNode
    
    Set node = head
    While Not node Is Nothing
        If node.value = value Then
            Exists = True
            Exit Function
        End If
        Set node = node.nextNode
    Wend
End Function

Public Function Count() As Long
    Dim node As SinglyLinkedNode
    
    Set node = head
    
    While Not node Is Nothing
        Count = Count + 1
        Set node = node.nextNode
    Wend
    
End Function