/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
if(list1==null){
return list2;
}else if(list2==null){
return list1;
}else if(list1.val<list2.val){
list1.next=mergeTwoLists(list1.next,list2);
return list1;
}else{
list2.next=mergeTwoLists(list2.next,list1);
return list2;
}
}
}