21. Merge Two Sorted Lists，mergesorted

21. Merge Two Sorted Lists，mergesorted

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.

代碼如下:

 1 /** 2  * Definition for singly-linked list. 3  * public class ListNode { 4  *     int val; 5  *     ListNode next; 6  *     ListNode(int x) { val = x; } 7  * } 8  */ 9 public class Solution {10     public ListNode mergeTwoLists(ListNode l1, ListNode l2) {11         if(l1==null&&l2==null)12         return null;13         if(l1==null&&l2!=null)14         return l2;15         if(l1!=null&&l2==null)16         return l1;17         18         ListNode head=l1.val<=l2.val?l1:l2;19         ListNode p=head;20         if(head==l1)21         l1=l1.next;22         else if(head==l2)23         l2=l2.next;24         25         while(l1!=null&&l2!=null)26         {27             head.next=l1.val<=l2.val?l1:l2;28         if(head.next==l1)29         l1=l1.next;30         else if(head.next==l2)31         l2=l2.next;32         head=head.next;33         }34         35         if(l1==null&&l2==null)36         head.next=null;37         if(l2!=null)38         head.next=l2;39         if(l1!=null)40         head.next=l1;41         42         return p;43     }44 }