LinkedList cycle detection using Flyod algorithm

cyclell1.java

/**
 * Definition for singly-linked list.
 * class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public boolean hasCycle(ListNode head) {
        // base case: if there are no nodes, there cannot be a cycle
        if (head == null) { return false; }
        // take 2 runners: the slow one starts at head and the fast one starts at one pointer beyond
        ListNode slow = head;
        ListNode fast = head.next;
        // if slow and fast are equal, that means the fast pointer came across a cycle and caught up with the slow pointer
        while (slow != fast) {
            // if fast is null or fast.next is null, that means the fast ptr has reached the end of the list and hasn't hit any cycle
            if (fast == null || fast.next == null) {
                return false;
            }
            // slow ptr moves slowly by one increments
            slow = slow.next;
            // fast pointer moves fast by 2 increments
            fast = fast.next.next;
        }
        return true;
    }
}