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//program to check for loops and count them in the list

import java.io.*;

import java.util.*;

class LinkedList

{

static class Node

{

int data;

Node next;

Node(int d)

{

data=d;

next=null;

}

}

static int count(Node n)

{

int tot=1;

Node temp = n;

while(temp.next != n)

{

tot++;

temp=temp.next;

}

return tot;

}

static int nodesinloop(Node no)

{

Node ptr1 = no, ptr2=no;

while(ptr1!=null && ptr2!=null && ptr2!=null)

{

ptr1 = ptr1.next; //moves a single node ahead

ptr2 = ptr2.next.next; //moves two nodes ahead

//if both meet at the same point then there is a loop

if(ptr1==ptr2)

{

return count(ptr1);

}

}

return 0;

}

static Node newnode(int element)

{

Node t = new Node(element);

return t;

}

public static void main(String argd[])

{

Node head = newnode(1);

head.next = newnode(2);

head.next.next = newnode(3);

head.next.next.next = newnode(4);

head.next.next.next.next = newnode(5);

head.next.next.next.next.next = newnode(6);

//we delibrately make a loop to test the code

head.next.next.next.next = head.next;

System.out.println(nodesinloop(head));

//let's try making another loop!

head.next.next.next.next.next = head.next;

System.out.println(nodesinloop(head));

}

}