腾讯五十题 No.30

题目链接

因为需要用到fast.next.next所以必须确保fast!=null && fast.next!=null，才能走到fast = fast.next.next;

public class Solution {
    public boolean hasCycle(ListNode head) {
        ListNode fast = head,slow = head;
        while(fast!=null && fast.next!=null){
            fast = fast.next.next;
            slow = slow.next;
            if(fast == slow){
                return true;
            }
        }
        return false;
    }
}