Challenge: Linked List Cycle—Hashing

Statement

Given the head of a linked list, check whether or not a cycle is present in the linked list. A cycle is present in a linked list if at least one node can be reached again by traversing the next pointer. If a cycle exists, return TRUE, otherwise return FALSE.

Constraints:

Let n be the number of nodes in a linked list.

• $0 \leq$ n $\leq 500$

• $-5 \times 10^3 \leq$ Node.value $\leq 5\times 10^3$

Examples