Error – found cycle in the listnode

ListNode

One of the most popular data structures in computer science is the linked list. Additionally, it is one of the simplest and serves as the foundation for more complex structures like stacks, circular buffers, and queues.

A list, in general, is a grouping of single data objects that are linked together through references. This is known as a pointer to C programmers. A data element might include information on an address, a location, a shape, a route, or a transaction, for instance. Every item in a linked list typically has the same list-specific data type.

To add a list node in java we can use the following approach.

Code

class Node {
    Object data;
    Node next;
    Node(Object d,Node n) {
        data = d ;
        next = n ;
       }

   public static Node addLast(Node header, Object x) {
       // save the reference to the header so we can return it.
       Node ret = header;

       // check base case, header is null.
       if (header == null) {
           return new Node(x, null);
       }

       // loop until we find the end of the list
       while ((header.next != null)) {
           header = header.next;
       }

       // set the new node to the Object x, next will be null.
       header.next = new Node(x, null);
       return ret;
   }
}

Cause of Error – found cycle in the listnode

The error-found cycle in the listnode occurs when the pointer points to the same node again and again while the loop runs. This may cause the loop to be infinite or in other words a cycle in the list that causes the error. 

The code snippet for the same can be:

Code

if (newpointer == null) {
    newpointer = newnode;
    mover = newpointer;
}
mover.next = newnode;

Here, the problem in the above code is that in the statements under the while loop, the mover and newnode point to the same object. This will lead the cycle edge to point to itself while the loop runs. 

Solution of Error – found cycle in the listnode

The code for the same can be a solution: 

Code

if (head == null) {
            head = cur;
        } else {
            prev.next = cur;
        }
        l1 = l1.next;
        l2 = l2.next;
        prev = cur;
    }

Here, the prev and next always point to a new pointer. The same is happening with the curr variable that does not lead to a cycle in the loop. Moreover, this one more solution to this problem can be by just simplifying the statements written in the code.

Also Read: Error: java: package org.junit.jupiter.api does not exist