Detect Cycle in Linked List

You are given the head of a singly linked list.

Determine whether the linked list contains a cycle.

A cycle exists if a node can be revisited by continuously following the next pointers.

Return:

1 if a cycle exists

0 if no cycle exists

You must solve this problem using O(1) extra space.

Input Format

[linked_list], pos

linked_list → list of node values

pos → index (0-based) where the last node connects

If pos = -1, there is no cycle

Example

[3,2,0,-4], 1

Output Format

1 or 0

Constraints

1 ≤ N ≤ 100000

-10⁹ ≤ Node values ≤ 10⁹

pos ∈ [-1, N-1]

Expected Time Complexity: O(N)

Expected Space Complexity: O(1)