leetcode刷题32

class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
ListNode demo=new ListNode(0);
ListNode current =demo;
while (l1!=null&&l2!=null){
if (l1.val<l2.val){
current.next=l1;
current=current.next;
l1=l1.next;
}else {
current.next=l2;
current=current.next;
l2=l2.next;
}
}
if (l1==null){
current.next=l2;
}else {
current.next=l1;
}
return demo.next;
}
}