LeetCode_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) {
        //head is NULL
        if(!head){
            return head;
        }
        
        ListNode *temp=head;
        ListNode *pretemp=NULL;
        ListNode *rotatePos=NULL;
        ListNode *preRotatePos=NULL;
        
        //calculate listLen
        int listLen=0;
        while(temp){
            temp=temp->next;
            listLen++;
        }
        //calculate the real num need to rotate
        int t=k%listLen;
        if(!t){
            return head;
        }
        
        temp=head;
        //find the kth ListNode from tail
        int i=0;
        while(i<t&&temp){
            i++;
            temp=temp->next;
        }
        //the list length is greater then k
        if (temp){
            rotatePos=head;
            while(temp){
                pretemp=temp;
                temp=temp->next;
                preRotatePos=rotatePos;
                rotatePos=rotatePos->next;
            }
        
            preRotatePos->next=NULL;
            pretemp->next=head;
            head=rotatePos;
        }
        return head;
    }
};