题解 | #判断链表中是否有环#

/**
 * 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) {

        if (head == null) {
            return false;
        }

        ListNode slowNode = head;
        ListNode fastNode = head;

        while (fastNode != null && fastNode.next != null) {

            fastNode = fastNode.next.next;
            slowNode = slowNode.next;

            if (slowNode == fastNode) {
                return true;
            }
        }

        return false;
    }
}