10. Fast & Slow Pointers

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

Output: true

Explanation: The linked list has a cycle where the tail connects to the second node (index 1).

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

Output: true

Explanation: The linked list has a cycle where the tail connects to the first node (index 0).

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

Output: false

Explanation: The linked list does not have a cycle.

Input: head = []

Output: false

Explanation: An empty linked list cannot have a cycle.

Time Complexity

O(n)

Space Complexity

O(1)