leetCode 23. Merge k Sorted Lists

 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 class Solution {
10     //返回lists数组第low至high位置(不包括high位置)的链表merge后的链表
11     public ListNode result(ListNode[] lists,int low,int high){
12         if (low+1==high) return lists[low];
13         int mid=(low+high)/2;
14         ListNode left = result(lists,low,mid);
15         ListNode right = result(lists,mid,high);
16 
17         //merge left链表和right链表
18         ListNode head = new ListNode(-65535);
19         ListNode p = head;//指向head最后一个节点
20         while (left!=null && right!=null){
21             if (left.val < right.val){
22                 p.next=left;
23                 left=left.next;
24             }else {
25                 p.next=right;
26                 right=right.next;
27             }
28             p=p.next;
29         }
30         if (left!=null){
31             p.next=left;
32         }
33         if (right!=null){
34             p.next=right;
35         }
36         return head.next;
37     }
38 
39     public ListNode mergeKLists(ListNode[] lists) {
40         if (lists.length==0) return null;
41         if (lists.length==1) return lists[0];
42         ListNode result = result(lists, 0, lists.length);
43         return result;
44     }
45 }