环形链表 II

这一题需要用数学公式推出来，代码随想录 (programmercarl.com) 还是看这个网站更清楚

public class Solution {public ListNode detectCycle(ListNode head) {ListNode fast=head;ListNode slow=head;while(fast!=null&&fast.next!=null){fast=fast.next.next;slow=slow.next;if(fast==slow){ListNode index1=fast;ListNode index2=head;while (index1 != index2) {index1 = index1.next;index2 = index2.next;}return index1;}}return null;}}