Merge Two Sorted Lists

 1 /**

 2  * Definition for singly-linked list.

 3  * public class ListNode {

 4  *     int val;

 5  *     ListNode next;

 6  *     ListNode(int x) {

 7  *         val = x;

 8  *         next = null;

 9  *     }

10  * }

11  */

12 public class Solution {

13     public ListNode mergeTwoLists(ListNode l1, ListNode l2) {

14         if(l1==null) return l2;

15         if(l2==null) return l1;

16         ListNode head=l1.val<l2.val?l1:l2;

17         ListNode current=l1.val<l2.val?l2:l1;

18         ListNode first=head;//记录head头 最后返回

19         

20         while(true)

21         {

22             if(head.next!=null)

23             {

24              if(head.next.val>current.val)

25              {　　//让head挪到current current挪到head.next

26                  ListNode temp=current;

27                  current=head.next;

28                  head.next=temp;

29                  head=temp;

30              }

31              else

32              head=head.next;

33             }

34             else

35             {　　//说明一个链表后面没有了

36                 head.next=current;

37                 break;

38             }

39         }

40         

41         return first;

42         

43         

44     }

45 }