How to Fix Error – Found Cycle In The ListNode [Fixed]

A linked list is a linear data structure in computer science responsible for providing constant time addition, and deleting elements. The linked list  consists of a sequence of nodes,  each node contains a value and a reference (called a “link”) to the next node in the same series.

Error – Found Cycle in the ListNode

The error – found cycle in the ListNode occurs if there is a problem with a linked list data structure, the case where  a node in the list has a reference to another node earlier in the list, thereby creating a cycle. This cycle can cause problems when repeating the  list, because the algorithm will never reach the end of the list and will end up in an infinite loop.

The below algorithmic code can generate an error – found cycle in the ListNode in a 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

From these examples, you can see we are trying to split a linked list into two separate lists:

One containing the odd-numbered nodes

The other containing the even-numbered nodes

The above code has a problem, the same linked list is used for both the odd and even lists. If you try to   modify the list by changing the next pointers of the nodes, it will cause errors if you try to iterate  the list again after the changes, because the structure of the list has been altered.

How to fix the Error – found cycle in the ListNode

In order To fix the error – found cycle in the ListNode issue; you have to create two separate linked lists for the odd and even nodes. Then add the nodes to the appropriate list while you iterate through an original linked list.

Here’s an example to help you fix 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.

Two separate lists for the odd and even nodes were created, and later the nodes were added to the appropriate list, and iterate through the original list.

This lists  also sets the next pointers of the last nodes in the odd and even lists to None to avoid creating a cycle, leading to the “error – found cycle in the ListNode”..

This approach proves efficient in solving the “error – found cycle in the ListNode”.