public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if (headA == null || headB == null) {
            return null;
        }
        ListNode p1 = headA;
        ListNode p2 = headB;
        int len1 = 0;
        int len2 = 0;
        while (p1 != null) {
            len1++;
            p1 = p1.next;
        }
        while (p2 != null) {
            len2++;
            p2 = p2.next;
        }
        p1 = headA;
        p2 = headB;
        if (len1 > len2) {
            for (int i = 0; i < len1 - len2; i++) {
                p1 = p1.next;
            }
        } else {
            for (int i = 0; i < len2 - len1; i++) {
                p2 = p2.next;
            }
        }
         while (p1 != p2) {
                p1 = p1.next;
                p2 = p2.next;
            }
            return p2;
    }