[LeetCode]21、Merge Two Sorted Lists

题目描述：

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.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

思路：

　　将两个排好序的链表合并，依次比较两个链表的数字，存入第三个链表中

 1 public class Solution21 {
 2     public ListNode mergeTwoLists(ListNode l1,ListNode l2){
 3         ListNode l3 = new ListNode(0);
 4         ListNode dummy = l3;
 5         while(l1 != null && l2 != null){
 6             if(l1.val< l2.val){
 7                 l3.next =l1;
 8                 l1 = l1.next;
 9             }else {
10                 l3.next = l2;
11                 l2 = l2.next;
12             }
13             l3 = l3.next;
14         }
15         l3.next = (l1 == null)?l2:l1;
16         return dummy.next;
17     }
18     public static void main(String[] args){
19         // TODO Auto-generated method stub
20         Solution21 solution21 = new Solution21();
21         ListNode l1 = new ListNode(1);
22         ListNode l2 = new ListNode(2);
23         
24         System.out.println(solution21.mergeTwoLists(l1, l2));
25     }
26 
27 }