Linked List Cycle Python Solution with Tests

lcpy gen -n 141   # by problem number
lcpy gen -s linked_list_cycle   # by problem name

Input: head = [3,2,0,-4], pos = 1
Output: true

Input: head = [1,2], pos = 0
Output: true

Input: head = [1], pos = -1
Output: false

from leetcode_py import ListNode


class Solution:
    # Time: O(n)
    # Space: O(1)
    def has_cycle(self, head: ListNode[int] | None) -> bool:
        fast = head
        slow = head

        while fast and fast.next:
            assert slow is not None
            fast = fast.next.next
            slow = slow.next
            if fast is slow:
                return True

        return False