[leetcode]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) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if(!head) return NULL;

int N = 0;
ListNode *end = head;
while(end->next){
end = end->next;
N++;
}
N++;

k = k%N;
if(k == 0) return head;

int M = N - k;

ListNode* p = head;
for(int i = 0; i < M-1; i++){
p = p->next;
}

ListNode *q = p->next;
p->next = NULL;
end->next = head;
return q;

}
};