[Leetcode] Distinct Subsequences

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode *rotateRight(ListNode *head, int k) {
12         if (head == NULL) return NULL;
13         ListNode *tail = head, *kth = head;
14         int n = 0;
15         while (tail != NULL) {
16             ++n;
17             tail = tail->next;
18         }
19         tail = head;
20         k %= n;
21         for (int i = 0; i < k; ++i) {
22             tail = tail->next;
23         }
24         while (tail != NULL && tail->next != NULL) {
25             tail = tail->next;
26             kth = kth->next;
27         }
28         if (tail != NULL) {
29             tail->next = head;
30             head = kth->next;
31             kth->next = NULL;
32         }
33         return head;
34     }
35 };