find_cycle_in_linked_list.py

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def hasCycle(self, head: ListNode) -> bool:
        if head and head.next:

            p1 = head.next
            p2 = head.next.next

            while p1 != p2 and (p1 and p2 and p2.next):
                p1 = p1.next
                p2 = p2.next.next


            if not (p1 and p2 and  p2.next):
                return False

            return True
        return False