VS2010 验证时出错。HRESULT = '8000000A'

Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?

CICT上有差不多的原题，

1. 初始化两个iterator都等于head， 设为a，b。
2. 每次迭代，a走一步，b走两步。
3. 如果a或者b走到null那就说明链表没有环，返回false，如果在某一步a==b则说明有环

/**
* Definition for singly-linked list.
* class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) {
*         val = x;
*         next = null;
*     }
* }
*/
public class Solution {
public boolean hasCycle(ListNode head) {
ListNode h1 = head;
ListNode h2 = head;

if(head == null){
return false;
}

while(true)
{
h1 = h1.next;
h2 = h2.next;
if( h1==null || h2 == null){
return false;
}else{
h2 = h2.next;
if(h2 == null){
return false;
}
}

if(h1 == h2){
return true;
}
}
}
}

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