Identify

• deal with a loop in a linked list or array
• involves something related to cyclic data structures like an Array or a Linked List
• you need to know the position of a certain element or the overall length of the linked list

Motive

• two pointers move through the data structure at different speeds and are going to meet eventually (the fast pointer should catch the slow pointer once both the pointers are in a cyclic loop)
• the fast pointer should catch the slow pointer once both the pointers are in a cyclic loop
• involves something related to cyclic data structures like an Array or a Linked List
• in some cases where you shouldn’t use the Two Pointer approach such as in a singly linked list where you can’t move in a backwards direction

Steps

• initiate two pointers: fast, slow = 0, 0
• iterate: while fast != slow:
• increase depending on problem +2, +1

Complexity

Time O(n)

Space O(1)

Common Problems

• [ ] Linked List Cycle (easy) Leetcode
• [ ] Start of LinkedList Cycle (medium) Leetcode