How do you detect a cycle in a linked list efficiently?

To detect a cycle in a linked list, I use Floyd's Cycle-Finding Algorithm, also known as the Tortoise and Hare algorithm. I initialize two pointers, slow and fast, both starting at the head. The slow pointer advances one node per iteration, while the fast pointer advances two nodes. If there is a cycle, the fast pointer will eventually catch up to the slow pointer inside the cycle. If the fast pointer reaches a null node, the list has no cycle. This approach uses O(1) space and O(n) time, making it highly efficient compared to using a hash set.