LeetCode 相交链表

 1 /* C++ */
 2 /**
 3  * Definition for singly-linked list.
 4  * struct ListNode {
 5  *     int val;
 6  *     ListNode *next;
 7  *     ListNode(int x) : val(x), next(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
13         if(headA == NULL || headB == NULL){
14             return NULL;
15         }
16         ListNode *a = headA;
17         ListNode *b = headB;
18         // 计算A和B的长度
19         int lenA = 0,lenB = 0;
20         while(a->next != NULL){
21             a = a->next;
22             lenA++;
23         }
24         while(b->next != NULL){
25             b = b->next;
26             lenB++;
27         }
28         int step = lenB - lenA;
29         if(step>0){
30             //说明B长
31             a = headB;
32             b = headA;
33         }else{// 说明A长
34             a = headA;
35             b = headB;
36             step *= -1;
37         }
38         while(step -- ){
39             a = a->next;
40         }
41         while(a != b){
42             a = a->next;b = b->next;
43         }
44         return a;
45     }
46 };