两个链表的第一个公共节点

 1 class Solution {
 2 public:
 3     int getLength(ListNode *pHead)
 4     {
 5         int count=0;
 6         while(pHead)
 7         {
 8             ++count;
 9             pHead=pHead->next;
10         }
11         return count;
12     }
13     ListNode* FindFirstCommonNode( ListNode* pHead1, ListNode* pHead2) {
14         if(pHead1==NULL || pHead2==NULL)return NULL;
15         int length1=getLength(pHead1);
16         int length2=getLength(pHead2);
17         while(length1>length2)
18         {
19             pHead1=pHead1->next;
20             --length1;
21         }
22         while(length2>length1)
23         {
24             pHead2=pHead2->next;
25             --length2;
26         }
27         while(pHead1 && pHead2)
28         {
29             if(pHead1==pHead2)return pHead1;
30             pHead1=pHead1->next;
31             pHead2=pHead2->next;
32         }
33         return NULL;
34     }
35 };