Visual Basic.NET How to Program (PDF)

Chapter 23 Data Structures and Collections 1151
3. If the list contains more than one node prior to removal, create the CListNode
reference current and assign it firstNode (line 101).
4. Use current to traverse the list until current references the node directly preceding
the last node. The While loop (lines 104–106) assigns current.NextNode
to reference current as long as current.NextNode is
not equal to lastNode.
5. After locating the second-to-last node, assign current to lastNode (line 109)
to dethread the last node from the list.
6. Set current.NextNode to Nothing (line 110) in the new last node of the list
to ensure proper list termination.
7. Return the removeItem reference (line 113).
Figure 23.11 illustrates method RemoveFromBack. Part a) illustrates the list before
the removal operation. Part b) portrays the actual reference manipulations.
Method Print (Fig. 23.5, lines 135–159) first determines whether the list is empty (line
139). If so, Print displays a String consisting of "Empty " and the list’s name and then
returns control to the calling method. Otherwise, Print outputs the data in the list. The
method prints a String consisting of the string "The ", the name of the list and the string
" is: ". Then, line 147 creates CListNode reference current and initializes it with
firstNode. While current is not Nothing, there are more items in the list. Therefore,
the method prints current.Data (line 151) then assigns current.NextNode to current
(line 152) thus moving to the next node in the list. Note that, if the link in the last node
of the list is not Nothing, the printing algorithm will erroneously attempt to print past the
end of the list. The printing algorithm is identical for linked lists, stacks and queues.
(a)
(b)
firstNode
12
firstNode
7 11
current
Fig. 23.11 RemoveFromBack graphical representation.
lastNode
5
lastNode
12 7 11
5
removeItem