C# program to detect a cycle in Linkedlist

Here's an example of a C# program that detects a cycle in a singly linked list:

using System;

class Node
{
    public int Data;
    public Node Next;

    public Node(int data)
    {
        Data = data;
        Next = null;
    }
}

class LinkedList
{
    private Node head;

    public void Add(int data)
    {
        Node newNode = new Node(data);

        if (head == null)
        {
            head = newNode;
        }
        else
        {
            Node current = head;
            while (current.Next != null)
            {
                current = current.Next;
            }
            current.Next = newNode;
        }
    }

    public bool DetectCycle()
    {
        if (head == null || head.Next == null)
        {
            return false; // No cycle in an empty or single-node linked list
        }

        Node slow = head;
        Node fast = head;

        while (fast != null && fast.Next != null)
        {
            slow = slow.Next;
            fast = fast.Next.Next;

            if (slow == fast)
            {
                return true; // Cycle detected
            }
        }

        return false; // No cycle detected
    }
}

class Program
{
    static void Main(string[] args)
    {
        LinkedList list = new LinkedList();

        // Creating a linked list with a cycle
        Node node1 = new Node(10);
        Node node2 = new Node(20);
        Node node3 = new Node(30);
        Node node4 = new Node(40);
        Node node5 = new Node(50);

        list.head = node1;
        node1.Next = node2;
        node2.Next = node3;
        node3.Next = node4;
        node4.Next = node5;
        node5.Next = node2; // Creating a cycle by connecting the last node to the second node

        // Detecting a cycle in the linked list
        bool hasCycle = list.DetectCycle();

        if (hasCycle)
        {
            Console.WriteLine("The linked list contains a cycle.");
        }
        else
        {
            Console.WriteLine("The linked list does not contain a cycle.");
        }
    }
}

This program creates a singly linked list class (LinkedList) that contains a private Node class. The Node class represents each node in the linked list and holds the data and a reference to the next node.

The LinkedList class provides two methods: Add and DetectCycle. The Add method adds a new node to the end of the linked list. The DetectCycle method uses the Floyd's Tortoise and Hare algorithm to detect a cycle in the linked list.

In the Main method, we create an instance of LinkedList and create a linked list with a cycle by connecting the last node to the second node. Then we call the DetectCycle method to check if the linked list contains a cycle. Depending on the result, we print whether the linked list contains a cycle or not.

The linked list contains a cycle.

This indicates that a cycle was successfully detected in the linked list.