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

<pre><code class=""language-java"" lang=""java"">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m1

while(p != q){
p = p.next;
q = q.next;
}
if(p == q)
return q;
}
}
return null;
}

</code></pre>

<pre><code> "“`