Imports System
Module ReverseLinkedList
' Node class for singly linked list
Public Class ListNode
Public Property Value As Integer ' data stored in the node
Public Property listNext As ListNode ' reference to the next node
Public Sub New(val As Integer)
Value = val
listNext = Nothing
End Sub
End Class
' Reverse the linked list in-place
Public Function ReverseList(head As ListNode) As ListNode
Dim prev As ListNode = Nothing ' will become the new head
Dim current As ListNode = head ' pointer to traverse the list
Dim nextNode As ListNode = Nothing ' temporary pointer to store next node
While current IsNot Nothing
nextNode = current.listNext ' save next node
current.listNext = prev ' reverse the link
prev = current ' move prev forward
current = nextNode ' move current forward
End While
Return prev ' prev is the new head
End Function
' Print the linked list
Public Sub PrintList(head As ListNode)
Dim temp As ListNode = head
While temp IsNot Nothing
Console.Write(temp.Value)
If temp.listNext IsNot Nothing Then
Console.Write(" -> ")
End If
temp = temp.listNext
End While
Console.WriteLine()
End Sub
Sub Main()
' Build a sample list: 1 -> 2 -> 3 -> 4 -> 5
Dim head As New ListNode(1)
head.listNext = New ListNode(2)
head.listNext.listNext = New ListNode(3)
head.listNext.listNext.listNext = New ListNode(4)
head.listNext.listNext.listNext.listNext = New ListNode(5)
Console.WriteLine("Original list:")
PrintList(head)
' Reverse the list
head = ReverseList(head)
Console.WriteLine("Reversed list:")
PrintList(head)
End Sub
End Module
' run:
'
' Original list:
' 1 -> 2 -> 3 -> 4 -> 5
' Reversed list:
' 5 -> 4 -> 3 -> 2 -> 1
'
