1struct ListNode
 2{
 3    int val;
 4    ListNode *next;
 5    ListNode(int x) : val(x), next(NULL) {}
 6};
 7
 8class Solution
 9{
10public:
11    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB)
12    {
13        ListNode *pA{headA}, *pB{headB};
14        while (pA != pB)
15        {
16            pA = pA == nullptr ? headB : pA->next;
17            pB = pB == nullptr ? headA : pB->next;
18        }
19        return pA;
20    }
21};