21. 合并两个有序链表

 1     public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
 2         ListNode dumy = new ListNode(0);
 3         pjin(dumy,l1,l2);
 4         return dumy.next;
 5     }
 6 
 7     public void pjin(ListNode cur,ListNode l1,ListNode l2){
 8         if(l1 == null){
 9             cur.next = l2;
10             return;
11         }else if(l2 == null){
12             cur.next = l1;
13             return;
14         }
15 
16         if(l1.val <= l2.val){
17             cur.next = l1;
18             pjin(l1,l1.next,l2);
19         }else {
20             cur.next = l2;
21             pjin(l2,l1,l2.next);
22         }
23 
24     }

 1 public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
 2         ListNode dumy = new ListNode(0);
 3         ListNode cur = dumy;
 4         while (l1 != null && l2 != null){
 5             if(l1.val <= l2.val){
 6                 cur.next = l1;
 7                 l1 = l1.next;
 8             }else {
 9                 cur.next = l2;
10                 l2 = l2.next;
11             }
12             cur = cur.next;
13         }
14         if(l1 == null){
15             cur.next = l2;
16         }else {
17             cur.next = l1;
18         }
19         return dumy.next;
20     }