【leetcode】61. 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.

 /**
  * 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==NULL||head->next==NULL||k==)
             return head;
         ListNode* bf=head;
         ListNode* newhead=head,*end=head;
         int length=;
         while(end->next!=NULL){
             end=end->next;
             length++;
         }
         end=head;
         if(k>length){
             k=k%length;
         }
         if(k==length||k==)
             return head;
         k--;
         while(k>&&end->next!=NULL){
             end=end->next;
             k--;
         }
         while(end->next!=NULL){
             end=end->next;
             bf=newhead;
             newhead=newhead->next;
         }

         bf->next=NULL;
         end->next=head;
         return newhead;

     }
 };