给单链表一个k数量节点的旋转。
开始WA，后来发现需要对k取mod。

class Solution {
public:
    ListNode *rotateRight(ListNode *head, int k) {
        int height = heightList(head);
        if(height == 0)return head;
        k %= height;
        if(height < k || head == NULL || head->next == NULL || k == 0)return head;
        k = height - k;
        ListNode * before = head;
        ListNode * now = head->next;
        k--;
        while(k > 0) {
            k--;
            before = now;
            now = now->next;
        }
        ListNode * tmp = head;
        while(tmp->next != NULL) {
            tmp = tmp->next;
        }
        tmp->next = head;
        before->next = NULL;
        return now;
    }
private:
    int heightList(ListNode * head) {
        int height = 0;
        while(head != NULL) {
            head = head->next;
            height++;
        }
        return height;
    }
};