Sandbox::https://github.com/prashanthigupta/leetcode-algorithms/blob/master/python/linked_list

Repository navigation

# Definition for singly-linked list.

class ListNode:

def __init__(self, x):

self.val = x

self.next = None

class Solution:

def not_null(self, head: ListNode) -> bool:

return head is not None

def hasCycle(self, head: ListNode) -> bool:

if head is None:

return False

slow, fast = head, head.next

while self.not_null(slow) and self.not_null(fast) and self.not_null(slow.next) and self.not_null(fast.next):

if slow is fast:

return True

slow = slow.next

fast = fast.next.next

return False