Find length of Loop Java

PROGRAM TO FIND THE LENGTH OF LOOP IN LINKED LIST

import java.io.*;

  

class MAIN {

      

  

/* Link list node */

static class Node 

{ 

    int data;

    Node next;

    Node(int data)

    {

        this.data =data;

        next =null;

    }

}

  

// Returns count of nodes present in loop. 

static int countNodes( Node n) 

{ 

int res = 1; 

Node temp = n; 

while (temp.next != n) 

{ 

    res++; 

    temp = temp.next; 

} 

return res; 

} 

  

/* This function detects and counts loop 

nodes in the list. If loop is not there 

in then returns 0 */

static int countNodesinLoop( Node list) 

{ 

    Node slow_p = list, fast_p = list; 

  

    while (slow_p !=null && fast_p!=null && fast_p.next!=null) 

    { 

        slow_p = slow_p.next; 

        fast_p = fast_p.next.next; 

  

        /* If slow_p and fast_p meet at some point 

        then there is a loop */

        if (slow_p == fast_p) 

            return countNodes(slow_p); 

    } 

  

    /* Return 0 to indeciate that ther is no loop*/

    return 0; 

} 

  

static Node newNode(int key) 

{ 

    Node temp = new Node(key);

      

    return temp; 

} 

  

/* Driver program to test above function*/

    public static void main (String[] args) {

        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); 

  

    /* Create a loop for testing */

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

  

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

    }

}




OUTPUT

4 

CREDITS: https://www.geeksforgeeks.org/find-length-of-loop-in-linked-list/