using System;
namespace ReverseLinkedListDemo
{
// Node class for singly linked list
public class ListNode
{
public int Value; // data stored in the node
public ListNode Next; // reference to the next node
public ListNode(int value)
{
Value = value;
Next = null;
}
}
class Program
{
// Reverse the linked list in-place
public static ListNode ReverseList(ListNode head)
{
ListNode prev = null; // will become the new head
ListNode current = head; // pointer to traverse the list
ListNode nextNode = null; // temporary pointer to store next node
while (current != null) {
nextNode = current.Next; // save next node
current.Next = prev; // reverse the link
prev = current; // move prev forward
current = nextNode; // move current forward
}
return prev; // prev is the new head
}
// Print the linked list
public static void PrintList(ListNode head)
{
ListNode temp = head;
while (temp != null) {
Console.Write(temp.Value);
if (temp.Next != null)
Console.Write(" -> ");
temp = temp.Next;
}
Console.WriteLine();
}
static void Main(string[] args)
{
// Build a sample list: 1 -> 2 -> 3 -> 4 -> 5
ListNode head = new ListNode(1);
head.Next = new ListNode(2);
head.Next.Next = new ListNode(3);
head.Next.Next.Next = new ListNode(4);
head.Next.Next.Next.Next = new ListNode(5);
Console.WriteLine("Original list:");
PrintList(head);
// Reverse the list
head = ReverseList(head);
Console.WriteLine("Reversed list:");
PrintList(head);
}
}
}
/*
run:
Original list:
1 -> 2 -> 3 -> 4 -> 5
Reversed list:
5 -> 4 -> 3 -> 2 -> 1
*/
