Rotate List

/**
 * 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 head;
            
        int length=1;
        ListNode *cur=head;
        
        while(cur->next)
        {
            ++length;
            cur=cur->next;
        }
        //become a circle
        cur->next=head;
        
        int count=1;
        cur=head;
        ListNode *ltcur;
        while(cur)
        {
            //using remained:important
            if(count==length-k%length)
            {
                ltcur=cur;
                break;
            }
            ++count;
            cur=cur->next;
        }
        //new head
        cur=ltcur->next;
        //break the circle
        ltcur->next=NULL;
        return cur;
    }
};