[leetcode]141. Linked List Cycle判断链表是否有环

 1 public class Solution {
 2     public boolean hasCycle(ListNode head) {
 3         ListNode fast = head;
 4         ListNode slow = head;
 5         while(fast != null && fast.next != null){
 6             fast = fast.next.next;
 7             slow = slow.next;
 8             if(fast == slow) return true;
 9         }
10         return false;
11     }
12 }