leetcode/solution/141_Linked_List_Cycle.py at master · CodexploreRepo/leetcode · GitHub

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class Solution:
    def hasCycle(self, head: ListNode) -> bool:
        if not head:
            return False
        slow = fast = head
        while fast and fast.next:
            slow = slow.next
            fast = fast.next.next
            if slow == fast:
                return True
        return False