ListNode *rotateRight(ListNode *head, int k) {

if(!head or k < 1) return head;

int len = 0;

ListNode *iter = head, *tail = head;

while(iter) {

len++;

tail = iter;

iter = iter->next;

}

iter = head;

k %= len;

if(k == 0) return head;

int cutPoint = len - k;

int i = 0;

while(i < cutPoint - 1) {

++i;

iter = iter->next;

}

ListNode *newHead = iter->next;

iter->next = NULL;

tail->next = head;

head = newHead;

return head;

}