struct ListNode
{
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};

class Solution
{
public:
    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB)
    {
        if (!headA || !headB)
            return NULL;
        ListNode *l1 = headA, *l2 = headB;
        while (l1 != l2)
        {
            l1 = l1 ? l1->next : headB;
            l2 = l2 ? l2->next : headA;
        }
        return l1;
    }
};