[Leetcode] Distinct Subsequences

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.

K可能会大于链表的长度，坑爹！

/**
 * 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 == NULL) return NULL;
        ListNode *tail = head, *kth = head;
        int n = 0;
        while (tail != NULL) {
            ++n;
            tail = tail->next;
        }
        tail = head;
        k %= n;
        for (int i = 0; i < k; ++i) {
            tail = tail->next;
        }
        while (tail != NULL && tail->next != NULL) {
            tail = tail->next;
            kth = kth->next;
        }
        if (tail != NULL) {
            tail->next = head;
            head = kth->next;
            kth->next = NULL;
        }
        return head;
    }
};