How to Fix error – found cycle in the listnode in LinkedList

A linked list is a linear data structure in computer science that consists of a sequence of nodes, where each node contains a value and a reference (called a “link”) to the next node in the series.

error – found cycle in the listnode

The error – found cycle in the listnode occurs when there is a problem with a linked list data structure, where a node in the list has a reference to another node earlier in the list, creating a cycle. The cycle can cause problems when iterating a list, as the algorithm will never reach the end of the list and may end up in an infinite loop.

See the below algorithmic code that generates an error – found cycle in the listnode in linked list data structure.

odd = head
even = head.next

while odd:
  if odd.next and odd.next.next:
    odd.next = odd.next.next
    odd = odd.next
  else:
    break

odd.next = even

In this algorithmic code, we are trying to split a linked list into two separate lists:

  1. Containing the odd-numbered nodes
  2. Containing the even-numbered nodes

The main problem with the above code is that we use the same linked list for both the odd and even lists. Therefore, you modify the list by changing the next pointers of the nodes, and it will cause errors if you try to iterate the list again after the changes, as the structure of the list has been changed.

How to Fix error – found cycle in the listnode

To fix the error – found cycle in the listnode issue, create two separate linked lists for the odd and even nodes, and add the nodes to the appropriate list while you iterate through an original linked list.

See the below algorithmic implementation to resolve the issue.

odd_list = ListNode(None)
even_list = ListNode(None)
odd_tail = odd_list
even_tail = even_list

current = head
is_odd = True

while current:
  if is_odd:
    odd_tail.next = current
    odd_tail = current
  else:
    even_tail.next = current
    even_tail = current

 is_odd = not is_odd
 current = current.next

odd_tail.next = None
even_tail.next = None

odd_head = odd_list.next
even_head = even_list.next

Let me explain this algorithm.

We created two separate lists for the odd and even nodes and added the nodes to the appropriate list as it iterated through the original list.

It also sets the next pointers of the last nodes in the odd and even lists to None to avoid creating a cycle.

This is the best and most efficient approach to solve error – found cycle in the listnode.

That’s it. Have a great holiday!

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.