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

使用快慢指针。 链表中快慢指针的妙用