链表是否有环
p1 = p2 = h;
do{
p1 = p1 ->next;
p2 = p2 ->next ->next;
}while(p2||p2->next||p1 == p2);
if(p1 == p2)
return true;
eles
return false;
文章标题：链表是否有环
文章起源：http://scyanting.com/article/jjdppd.html
