141. Linked List Cycle

Please refer to LeetCode for the question details:

https://leetcode.com/problems/linked-list-cycle/description/

We are asked check if a Linked List contains a cycle.

Intuition

Slow and fast pointers pattern is used to find cycle in a linked list

Approach

1. Initialize slow and fast pointer with the head of the linkedList
2. Move slow pointer by one step, and fast pointer by two steps.
3. Repeat step 3 until one of the following conditions are met: i. fast is null or fast.next is null. No Cycle ii. fast is equal to slow. Found cycle

Complexity

• Time complexity: O(n)
• Space complexity: O(1)

Code

Here are the performance metrics:

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https://leetcode.com/problems/linked-list-cycle/solutions/4830189/interview-solution-time-on-space-o1-beats-9655