Detect cycle in a linked list in linear time

Here given code implementation process.

/*
  Java program
  Detect cycle in a linked list in linear time
*/
import java.util.Set;
import java.util.HashSet;

// Linked list node
class LinkNode
{
    public int data;
    public LinkNode next;
    public LinkNode(int data)
    {
        this.data = data;
        this.next = null;
    }
}

public class LoopDetection
{
    // Check whether given linked list contains loop or not
    public void findLoop(LinkNode head)
    {
        // Use to collect unique nodes
        Set<LinkNode> result = new HashSet<LinkNode>();

        // Loop indicators
        Boolean status = false;

        // Start with first node
        LinkNode node = head;

        // iterate linked list nodes
        while (node != null && status == false)
        {
            if (result.contains(node))
            {
                status = true;
            }
            else
            {
                // Display node value
                System.out.print("  " + (node.data));
                // Add node
                result.add(node);
            }
            // Visit to next node
            node = node.next;
        }
        if (status == true)
        {
            System.out.print("\n  Loop are exist\n");
        }
        else
        {
            System.out.print("\n  Loop are not exist\n");
        }
    }
    public static void main(String[] args)
    {
        LoopDetection task = new LoopDetection();
       
        LinkNode head = new LinkNode(1);
        head.next = new LinkNode(2);
        head.next.next = new LinkNode(3);
        head.next.next.next = new LinkNode(4);
        head.next.next.next.next = new LinkNode(5);
        head.next.next.next.next.next = new LinkNode(6);
        // 1 → 2 → 3 → 4 → 5 → 6 → NULL
        task.findLoop(head);
        // Create a loop 
        head.next.next.next.next.next.next = head.next.next;
        
        // 1 → 2 → 3 → 4 → 5 → 6 ──┐
        //         └───────────────┘                 
        // Test
        task.findLoop(head);
    }
}

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
// Include header file
#include <iostream>
#include <set>
using namespace std;

// Linked list node
class LinkNode
{
	public: int data;
	LinkNode *next;
	LinkNode(int data)
	{
		this->data = data;
		this->next = NULL;
	}
};
class LoopDetection
{
	public:
		// Check whether given linked list contains loop or not
		void findLoop(LinkNode *head)
		{
			// Use to collect unique nodes
			set <LinkNode*> result;
			// Loop indicators
			bool status = false;
			// Start with first node
			LinkNode *node = head;
			// iterate linked list nodes
			while (node != NULL && status == false)
			{
				if (result.find(node) != result.end())
				{
					status = true;
				}
				else
				{
					// Display node value
					cout << "  " << (node->data);
					result.insert(node);
				}
				// Visit to next node
				node = node->next;
			}
			if (status == true)
			{
				cout << "\n  Loop are exist\n";
			}
			else
			{
				cout << "\n  Loop are not exist\n";
			}
		}
};
int main()
{
	LoopDetection task = LoopDetection();
	LinkNode *head = new LinkNode(1);
	head->next = new LinkNode(2);
	head->next->next = new LinkNode(3);
	head->next->next->next = new LinkNode(4);
	head->next->next->next->next = new LinkNode(5);
	head->next->next->next->next->next = new LinkNode(6);
	// 1 → 2 → 3 → 4 → 5 → 6 → NULL
	task.findLoop(head);
	// Create a loop
	head->next->next->next->next->next->next = head->next->next;
	// 1 → 2 → 3 → 4 → 5 → 6 ──┐
	//         └───────────────┘
	// Test
	task.findLoop(head);
	return 0;
}

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
// Include namespace system
using System;
using System.Collections.Generic;
/*
  C# program
  Detect cycle in a linked list in linear time
*/
// Linked list node
public class LinkNode
{
	public int data;
	public LinkNode next;
	public LinkNode(int data)
	{
		this.data = data;
		this.next = null;
	}
}
public class LoopDetection
{
	// Check whether given linked list contains loop or not
	public void findLoop(LinkNode head)
	{
		// Use to collect unique nodes
		HashSet < LinkNode > result = new HashSet < LinkNode > ();
		// Loop indicators
		Boolean status = false;
		// Start with first node
		LinkNode node = head;
		// iterate linked list nodes
		while (node != null && status == false)
		{
			if (result.Contains(node))
			{
				status = true;
			}
			else
			{
				// Display node value
				Console.Write("  " + (node.data));
				result.Add(node);
			}
			// Visit to next node
			node = node.next;
		}
		if (status == true)
		{
			Console.Write("\n  Loop are exist\n");
		}
		else
		{
			Console.Write("\n  Loop are not exist\n");
		}
	}
	public static void Main(String[] args)
	{
		LoopDetection task = new LoopDetection();
		LinkNode head = new LinkNode(1);
		head.next = new LinkNode(2);
		head.next.next = new LinkNode(3);
		head.next.next.next = new LinkNode(4);
		head.next.next.next.next = new LinkNode(5);
		head.next.next.next.next.next = new LinkNode(6);
		// 1 → 2 → 3 → 4 → 5 → 6 → NULL
		task.findLoop(head);
		// Create a loop
		head.next.next.next.next.next.next = head.next.next;
		// 1 → 2 → 3 → 4 → 5 → 6 ──┐
		//         └───────────────┘
		// Test
		task.findLoop(head);
	}
}

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
<?php
/*
  Php program
  Detect cycle in a linked list in linear time
*/
// Linked list node
class LinkNode
{
	public $data;
	public $next;

	function __construct($data)
	{
		$this->data = $data;
		$this->next = null;
	}
}
class LoopDetection
{
	// Check whether given linked list contains loop or not
	public	function findLoop($head)
	{
		// Use to collect unique nodes
		$result = array();
		// Loop indicators
		$status = false;
		// Start with first node
		$node = $head;
		// iterate linked list nodes
		while ($node != null && $status == false)
		{
			if (($key = array_search($node, $result) !== false))
			{
				$status = true;
			}
			else
			{
				// Display node value
				echo "  ". ($node->data);
				$result[] = $node;
			}
			// Visit to next node
			$node = $node->next;
		}
		if ($status == true)
		{
			echo "\n  Loop are exist\n";
		}
		else
		{
			echo "\n  Loop are not exist\n";
		}
	}
}

function main()
{
	$task = new LoopDetection();
	$head = new LinkNode(1);
	$head->next = new LinkNode(2);
	$head->next->next = new LinkNode(3);
	$head->next->next->next = new LinkNode(4);
	$head->next->next->next->next = new LinkNode(5);
	$head->next->next->next->next->next = new LinkNode(6);
	// 1 → 2 → 3 → 4 → 5 → 6 → NULL
	$task->findLoop($head);
	// Create a loop
	$head->next->next->next->next->next->next = $head->next->next;
	// 1 → 2 → 3 → 4 → 5 → 6 ──┐
	//         └───────────────┘
	// Test
	$task->findLoop($head);
}
main();

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
/*
  Node Js program
  Detect cycle in a linked list in linear time
*/
// Linked list node
class LinkNode
{
	constructor(data)
	{
		this.data = data;
		this.next = null;
	}
}
class LoopDetection
{
	// Check whether given linked list contains loop or not
	findLoop(head)
	{
		// Use to collect unique nodes
		var result = new Set();
		// Loop indicators
		var status = false;
		// Start with first node
		var node = head;
		// iterate linked list nodes
		while (node != null && status == false)
		{
			if (result.has(node))
			{
				status = true;
			}
			else
			{
				// Display node value
				process.stdout.write("  " + (node.data));
				result.add(node);
			}
			// Visit to next node
			node = node.next;
		}
		if (status == true)
		{
			process.stdout.write("\n  Loop are exist\n");
		}
		else
		{
			process.stdout.write("\n  Loop are not exist\n");
		}
	}
}

function main()
{
	var task = new LoopDetection();
	var head = new LinkNode(1);
	head.next = new LinkNode(2);
	head.next.next = new LinkNode(3);
	head.next.next.next = new LinkNode(4);
	head.next.next.next.next = new LinkNode(5);
	head.next.next.next.next.next = new LinkNode(6);
	// 1 → 2 → 3 → 4 → 5 → 6 → NULL
	task.findLoop(head);
	// Create a loop
	head.next.next.next.next.next.next = head.next.next;
	// 1 → 2 → 3 → 4 → 5 → 6 ──┐
	//         └───────────────┘
	// Test
	task.findLoop(head);
}
main();

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
#   Python 3 program
#   Detect cycle in a linked list in linear time

#  Linked list node
class LinkNode :
	
	def __init__(self, data) :
		self.data = data
		self.next = None
	

class LoopDetection :
	#  Check whether given linked list contains loop or not
	def findLoop(self, head) :
		#  Use to collect unique nodes
		result = set()
		#  Loop indicators
		status = False
		#  Start with first node
		node = head
		#  iterate linked list nodes
		while (node != None and status == False) :
			if (node in result) :
				status = True
			else :
				#  Display node value
				print(" ", (node.data), end = "")
				#  Add node
				result.add(node)
			
			#  Visit to next node
			node = node.next
		
		if (status == True) :
			print("\n  Loop are exist")
		else :
			print("\n  Loop are not exist")
		
	

def main() :
	task = LoopDetection()
	head = LinkNode(1)
	head.next = LinkNode(2)
	head.next.next = LinkNode(3)
	head.next.next.next = LinkNode(4)
	head.next.next.next.next = LinkNode(5)
	head.next.next.next.next.next = LinkNode(6)
	#  1 → 2 → 3 → 4 → 5 → 6 → NULL
	task.findLoop(head)
	#  Create a loop 
	head.next.next.next.next.next.next = head.next.next
	#  1 → 2 → 3 → 4 → 5 → 6 ──┐
	#          └───────────────┘                 
	#  Test
	task.findLoop(head)

if __name__ == "__main__": main()

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
#   Ruby program
#   Detect cycle in a linked list in linear time

#  Linked list node
class LinkNode  
	# Define the accessor and reader of class LinkNode  
	attr_reader :data, :next
	attr_accessor :data, :next
 
	def initialize(data) 
		self.data = data
		self.next = nil
	end
end

class LoopDetection 
	#  Check whether given linked list contains loop or not
	def findLoop(head) 
		#  Use to collect unique nodes
		result = []
		#  Loop indicators
		status = false
		#  Start with first node
		node = head
		#  iterate linked list nodes
		while (node != nil && status == false) 
			if (result.include?(node)) 
				status = true
			else 
				#  Display node value
				print("  ", (node.data))
				result.push(node)
			end

			#  Visit to next node
			node = node.next
		end

		if (status == true) 
			print("\n  Loop are exist\n")
		else 
			print("\n  Loop are not exist\n")
		end

	end

end

def main() 
	task = LoopDetection.new()
	head = LinkNode.new(1)
	head.next = LinkNode.new(2)
	head.next.next = LinkNode.new(3)
	head.next.next.next = LinkNode.new(4)
	head.next.next.next.next = LinkNode.new(5)
	head.next.next.next.next.next = LinkNode.new(6)
	#  1 → 2 → 3 → 4 → 5 → 6 → NULL
	task.findLoop(head)
	#  Create a loop 
	head.next.next.next.next.next.next = head.next.next
	#  1 → 2 → 3 → 4 → 5 → 6 ──┐
	#          └───────────────┘                 
	#  Test
	task.findLoop(head)
end

main()

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
import scala.collection.mutable._;
/*
  Scala program
  Detect cycle in a linked list in linear time
*/
// Linked list node
class LinkNode(var data: Int , var next: LinkNode)
{
	def this(data: Int)
	{
		this(data, null);
	}
}
class LoopDetection
{
	// Check whether given linked list contains loop or not
	def findLoop(head: LinkNode): Unit = {
		// Use to collect unique nodes
		var result: Set[LinkNode] = Set();
		// Loop indicators
		var status: Boolean = false;
		// Start with first node
		var node: LinkNode = head;
		// iterate linked list nodes
		while (node != null && status == false)
		{
			if (result.contains(node))
			{
				status = true;
			}
			else
			{
				// Display node value
				print("  " + (node.data));
				result.add(node);
			}
			// Visit to next node
			node = node.next;
		}
		if (status == true)
		{
			print("\n  Loop are exist\n");
		}
		else
		{
			print("\n  Loop are not exist\n");
		}
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var task: LoopDetection = new LoopDetection();
		var head: LinkNode = new LinkNode(1);
		head.next = new LinkNode(2);
		head.next.next = new LinkNode(3);
		head.next.next.next = new LinkNode(4);
		head.next.next.next.next = new LinkNode(5);
		head.next.next.next.next.next = new LinkNode(6);
		// 1 → 2 → 3 → 4 → 5 → 6 → NULL
		task.findLoop(head);
		// Create a loop
		head.next.next.next.next.next.next = head.next.next;
		// 1 → 2 → 3 → 4 → 5 → 6 ──┐
		//         └───────────────┘
		// Test
		task.findLoop(head);
	}
}

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist
/*
  Swift 4 program
  Detect cycle in a linked list in linear time
*/
// Linked list node
class LinkNode
{
	var data: Int;
	var next: LinkNode? ;
	init(_ data: Int)
	{
		self.data = data;
		self.next = nil;
	}
}
class LoopDetection
{
	// Check whether given linked list contains loop or not
	func findLoop(_ head: LinkNode? )
	{
		// Use to collect unique nodes
		var result = [LinkNode]()
		// Loop indicators
		var status: Bool? = false;
		// Start with first node
		var node: LinkNode? = head;
		// iterate linked list nodes
		while (node  != nil && status == false)
		{
			if (result.contains(where: {$0 === node}))
			{
				status = true;
			}
			else
			{
				// Display node value
				print("  ", (node!.data), terminator: "");
				result.append(node!);
			}
			// Visit to next node
			node = node!.next;
		}
		if (status == true)
		{
			print("\n  Loop are exist");
		}
		else
		{
			print("\n  Loop are not exist");
		}
	}
}
func main()
{
	let task: LoopDetection = LoopDetection();
	let head: LinkNode? = LinkNode(1);
	head!.next = LinkNode(2);
	head!.next!.next = LinkNode(3);
	head!.next!.next!.next = LinkNode(4);
	head!.next!.next!.next!.next = LinkNode(5);
	head!.next!.next!.next!.next!.next = LinkNode(6);
	// 1 → 2 → 3 → 4 → 5 → 6 → NULL
	task.findLoop(head);
	// Create a loop
	head!.next!.next!.next!.next!.next!.next = head!.next!.next;
	// 1 → 2 → 3 → 4 → 5 → 6 ──┐
	//         └───────────────┘
	// Test
	task.findLoop(head);
}
main();

Output

   1   2   3   4   5   6
  Loop are not exist
   1   2   3   4   5   6
  Loop are exist
/*
  Kotlin program
  Detect cycle in a linked list in linear time
*/
// Linked list node
class LinkNode
{
	var data: Int;
	var next: LinkNode ? ;
	constructor(data: Int)
	{
		this.data = data;
		this.next = null;
	}
}
class LoopDetection
{
	// Check whether given linked list contains loop or not
	fun findLoop(head: LinkNode ? ): Unit
	{
		// Use to collect unique nodes
		var result: MutableSet <LinkNode> = mutableSetOf <LinkNode> ();
		// Loop indicators
		var status: Boolean ? = false;
		// Start with first node
		var node: LinkNode ? = head;
		// iterate linked list nodes
		while (node != null && status == false)
		{
			if (result.contains(node))
			{
				status = true;
			}
			else
			{
				// Display node value
				print("  " + (node.data));
				result.add(node);
			}
			// Visit to next node
			node = node.next;
		}
		if (status == true)
		{
			print("\n  Loop are exist\n");
		}
		else
		{
			print("\n  Loop are not exist\n");
		}
	}
}
fun main(args: Array < String > ): Unit
{
	var task: LoopDetection = LoopDetection();
	var head: LinkNode = LinkNode(1);
	head.next = LinkNode(2);
	head.next?.next = LinkNode(3);
	head.next?.next?.next = LinkNode(4);
	head.next?.next?.next?.next = LinkNode(5);
	head.next?.next?.next?.next?.next = LinkNode(6);
	// 1 → 2 → 3 → 4 → 5 → 6 → NULL
	task.findLoop(head);
	// Create a loop
	head.next?.next?.next?.next?.next?.next = head.next?.next;
	// 1 → 2 → 3 → 4 → 5 → 6 ──┐
	//         └───────────────┘
	// Test
	task.findLoop(head);
}

Output

  1  2  3  4  5  6
  Loop are not exist
  1  2  3  4  5  6
  Loop are exist


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