Leetcode#160 Intersection of Two Linked Lists

 1 ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
 2         if (!headA || !headB)
 3             return NULL;
 4             
 5         ListNode *h = headA;
 6         while (h->next)
 7             h = h->next;
 8         h->next = headB;
 9         
10         ListNode *fast = headA;
11         ListNode *slow = headA;
12         bool running = false;
13         ListNode *res = NULL;
14         
15         while ((!running || fast != slow) && fast && fast->next) {
16             running = true;
17             fast = fast->next->next;
18             slow = slow->next;
19         }
20         if (fast == slow) {
21             res = headA;
22             while (res != slow) {
23                 res = res->next;
24                 slow = slow->next;
25             }
26         }
27         h->next = NULL;
28         
29         return res;
30 }