手写代码：怎么判断链表有环，怎么找环节点?

参考回答：

判断是否有环以及环节点

public class Solution {ListNode EntryNodeOfLoop(ListNode h){if(h == null || h.next == null)return null;ListNode slow = h;ListNode fast = h;while(fast != null && fast.next != null ){slow = slow.next;fast = fast.next.next;if(slow == fast){ListNode p=h;ListNode q=slow;//相当于让q指向了m1while(p != q){    p = p.next;    q = q.next;    }    if(p == q)    return q;    }    }    return null;}