给出俩个单向链表的头指针，比如h1，h2，判断这俩个链表是否相交。

为了简化问题，我们假设俩个链表均不带环。

问题扩展：

1.如果链表可能有环列?

2.如果需要求出俩个链表相交的第一个节点列?

ANSWER: 

 struct Node {
   int data;
   int Node *next;
 };
 // if there is no cycle.
 int isJoinedSimple(Node * h1, Node * h2) {
   while (h1->next != NULL) {
     h1 = h1->next;
   }
   while (h2->next != NULL) {
     h2 = h2-> next;
   }
   return h1 == h2;
 }
 // if there could exist cycle
 int isJoined(Node *h1, Node * h2) {
   Node* cylic1 = testCylic(h1);
   Node* cylic2 = testCylic(h2);
   if (cylic1+cylic2==0) return isJoinedSimple(h1, h2);
   if (cylic1==0 && cylic2!=0 || cylic1!=0 &&cylic2==0) return 0;
   Node p = cylic1;
   while (1) {     if (p==cylic2 || p->next == cylic2) return 1;
     p=p->next->next; 
    cylic1 = cylic1->next;
     if (p==cylic1) return 0;   } } Node testCylic(Node * h1) {
   Node * p1 = h1, *p2 = h1;
   while (p2!=NULL && p2->next!=NULL) {
     p1 = p1->next;
     p2 = p2->next->next;
     if (p1 == p2) {
       return p1;
     }
   }
   return NULL;}