https://oj.leetcode.com/problems/linked-list-cycle-ii/
http://blog.csdn.net/linhuanmars/article/details/21260943
/**
* Definition for singly-linked list.
* class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public ListNode detectCycle(ListNode head) {
if (head == null)
return null;
ListNode one = head;
ListNode two = head;
ListNode meet = null;
while (one != null && two != null)
{
one = one.next;
two = two.next;
if (two == null)
return null;
else
two = two.next;
if (one == two)
{
meet = one;
break;
}
}
if (meet == null)
return null; // no cicle.
one = head;
while (one != two)
{
one = one.next;
two = two.next;
}
return one;
}
}[LeetCode]142 Linked List Cycle II
原文：http://7371901.blog.51cto.com/7361901/1600801