Rotate List

 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         
14         // first find the (n - k % n)th element
15         ListNode* move = head;
16         int count = 1;
17         while(move->next) {
18             count++;
19             move = move->next;
20         }
21         ListNode* endNode = move;
22         
23         k %= count;
24         move = head;
25         int index = 0;
26         while(index++ < k)
27             move = move->next;
28     
29         ListNode* current = head;
30         while(move->next) {
31             move = move->next;
32             current = current->next;
33         }
34         endNode->next = head;
35         head = current->next;
36         current->next = NULL;
37        
38         return head;
39     }
40 };