【leetcode】Intersection of Two Linked Lists

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
12        
13        
14         if(headA==NULL||headB==NULL)
15         {
16             return NULL;
17         }
18        
19         ListNode *hA=headA,*hB=headB;
20        
21         int lenA=1,lenB=1;
22         while(hA->next!=NULL)
23         {
24             lenA++;
25             hA=hA->next;
26         }
27        
28         while(hB->next!=NULL)
29         {
30             lenB++;
31             hB=hB->next;
32         }
33        
34        
35         if(hA!=hB)
36         {
37             return NULL;
38         }
39        
40         int dis=lenA-lenB;
41        
42        
43         hA=headA;
44         hB=headB;
45        
46         if(dis>0)
47         {
48             while(dis)
49             {
50                 hA=hA->next;
51                 dis--;
52             }
53         }
54        
55         if(dis<0)
56         {
57             dis=-dis;
58             while(dis)
59             {
60                 hB=hB->next;
61                 dis--;
62             }
63         }         
64        
65         while(hA!=hB)
66         {
67             hA=hA->next;
68             hB=hB->next;
69         }
70        
71        
72         return hA;
73     }
74 };
75