Rotate List

Given a list, rotate the list to the right by k places, where k is non-negative.

Example

Given 1->2->3->4->5 and k = 2, return 4->5->1->2->3.

思路：画图。 

 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     /**
14      * @param head: the List
15      * @param k: rotate to the right k places
16      * @return: the list after rotation
17      */
18     public ListNode rotateRight(ListNode head, int k) {
19         if (head == null || head.next == null) {
20             return head;
21         }
22         
23         ListNode dummy = new ListNode(0);
24         dummy.next = head;
25         ListNode node = dummy;
26         int length = 0;
27         while (node.next != null) {
28             ++length;
29             node = node.next;
30         }
31         node = dummy;
32         for (int i = 0; i < length - (k % length); i++) {
33             node = node.next;
34         }
35         ListNode tail = node;
36         while (tail.next != null) {
37             tail = tail.next;
38         }
39         tail.next = dummy.next;
40         dummy.next = node.next;
41         node.next = null;
42         return dummy.next;
43     }
44 }

 

posted @ 2016-04-23 09:14  YuriFLAG  阅读(121)  评论(0)    收藏  举报