上班摸鱼刷算法-Java-hot100-[141]环形链表

//快慢指针
public class Solution {
    public boolean hasCycle(ListNode head) {
        if (head == null || head.next == null) {
            return false;
        }
        ListNode fastNode = head.next;
        ListNode slowNode = head;

        while (fastNode != slowNode) {
            if (fastNode == null || fastNode.next == null) {
                return false;
            }
            fastNode = fastNode.next.next;
            slowNode = slowNode.next;
        }
        return true;
    }
}