Leetcode - Linked List Cycle

Question

Given head, the head of a linked list, determine if the linked list has a cycle in it.

There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the next pointer. Internally, pos is used to denote the index of the node that tail’s next pointer is connected to. Note that pos is not passed as a parameter.

Return true if there is a cycle in the linked list. Otherwise, return false.

This is a linked_list question.

Idea

• The whole point is to check to see if I’ve seen a specific node before (node, not value)
• Keep a set, check if our head is in the set, if so, return True, if not add head to the set
• Move head on to the next
• If we iterate throughout the linked list (we break the while look), return False

Solution