21. 合并两个有序链表

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
ListNode l_new=new ListNode(-1);
ListNode l0=l_new;
while(l1 != null && l2 != null ){
if(l1.val<l2.val){
l0.next=l1;
l0=l0.next;
l1=l1.next;
}
else {
l0.next=l2;
l0=l0.next;
l2=l2.next;
}
}

if(l1!=null)l0.next=l1;
if(l2!=null)l0.next=l2;

return l_new.next;
}
}