public class Solution {

    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {

        if(headA == null || headB == null) return null;

        ListNode a = headA;

        ListNode b = headB;

        while(a != b){

            a = a == null ? headB : a.next;

            b = b == null ? headA : b.next;

        }

        return a;

    }

}

 */

class Solution {

    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {

        if(l1 == null) return l2;

        if(l2 == null) return l1;

        if(l1.val < l2.val){

            l1.next = mergeTwoLists(l1.next, l2);

            return l1;

        }else{

            l2.next = mergeTwoLists(l1, l2.next);

            return l2;

        }

    }

}