Rotate List

来源：Leetcode

原帖：http://oj.leetcode.com/problems/rotate-list/

题目：
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.
Solution: Notice that k can be larger than the list size (k % list_size). This solution traverses the list twice at most.

代码：

 /**  
  * Definition for singly-linked list.  
  * struct ListNode {  
  *   int val;  
  *   ListNode *next;  
  *   ListNode(int x) : val(x), next(NULL) {}  
  * };  
  */  
 class Solution {  
 public:  
     ListNode *rotateRight(ListNode *head, int k) {  
         if (!head) return NULL;  
         ListNode* tail = head;  
         int length = 1;  
         while (tail->next) {  
             tail = tail->next;  
             length++;  
         }  
         k = k % length; // edge case: the list rotates more than one round.  
         if (k == 0) return head;  
         ListNode* cur = head;  
         for (int i = 0; i < length - k - 1; i++) {  
             cur = cur->next;        
         }  
         ListNode* newHead = cur->next;  
         cur->next = NULL;  
         tail->next = head;  
         return newHead;  
     }  
 };