21. Merge Two Sorted Lists(合并2个有序链表)

21. Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists

需要排序！！！

[2,4]
[1]

输出1 2 4

而不是2 4 1

 递归版！！

 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(l2.next,l1);
             return l2;
         }

     }

 }