【剑指offer】两个链表的第一个公共结点

 1 /*
 2 struct ListNode {
 3     int val;
 4     struct ListNode *next;
 5     ListNode(int x) :
 6             val(x), next(NULL) {
 7     }
 8 };*/
 9 class Solution {
10 public:
11     ListNode* FindFirstCommonNode( ListNode* pHead1, ListNode* pHead2) {
12         ListNode* p1 = pHead1;
13         ListNode* p2 = pHead2;
14         int len1 = 0,len2 = 0;
15         //链表长度
16         while(p1){    len1++; p1=p1->next;}
17         while(p2){    len2++; p2=p2->next;}
18         //相差
19         int sub = abs(len1-len2);
20         if(len1 > len2){
21             while(sub){
22                 pHead1 = pHead1->next;sub--;    //链表1先走
23             }
24         }
25         else{
26             while(sub){
27                 pHead2 = pHead2->next;sub--;    //链表2先走
28             }
29         }
30         //同时向后走
31         while(pHead1){
32             if(pHead1 == pHead2)    return pHead1;
33             pHead1 = pHead1->next;
34             pHead2 = pHead2->next;
35         }
36         return NULL;
37     }
38 };