Rotate List

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

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

分析：首先遍历list得到长度，然后找到应该rotate的位置，进行rotate。注意：k有可能大于长度，因此要进行取模运算。

运行时间：12ms

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode* rotateRight(ListNode* head, int k) {
12         if(!head || !head->next) return head;
13         if(k == 0) return head;
14         
15         int len = 0;
16         ListNode* move = head;
17         while(move->next){ // find the end of the list
18             len++;
19             move = move->next;
20         }
21         ListNode* end = move;
22         len++; // length of the list
23         
24         int count = 0;
25         move->next = head;
26         while(count < len - k % len){ // find the position of the rotating node
27             count++;
28             move = move->next;  // move is the position of the node before the rotating node
29         }
30         ListNode* rotate = move->next; // rotate is the position of the rotating node
31         
32         end->next = head;
33         move->next = NULL;
34         return rotate;
35     }
36 };