代码实现：

方法一：在原链表中找到旋转之后的首尾，改变指向

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     struct ListNode *next;* };*/
struct ListNode* rotateRight(struct ListNode *head, int k) {if (k == 0 || head == NULL || head->next == NULL) {return head;}int n = 1;struct ListNode *p = head;while (p->next != NULL) {p = p->next;n++;}int add = n - k % n;if (add == n) {return head;}p->next = head;while (add--) {p = p->next;}struct ListNode *ret = p->next;p->next = NULL;return ret;
}

方法二：反转链表

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     struct ListNode *next;* };*/
// 反转链表
struct ListNode* nizhi(struct ListNode *head) {if (head == NULL || head->next == NULL) {return head;}struct ListNode *tail = head->next;struct ListNode *new_head = nizhi(head->next);head->next = tail->next;tail->next = head;return new_head;
}struct ListNode* rotateRight(struct ListNode *head, int k) {if (head == NULL || head->next == NULL || k == 0) {return head;}int len = 0;struct ListNode *p = head;while (p) {len++;p = p->next;}int n = k % len;if (n == 0) {return head;}head = nizhi(head);struct ListNode *h = head, *p1 = head;struct ListNode *p2 = head, *p3;while (n - 1) {p2 = p2->next;n--;}p3 = p2->next;p2->next = NULL;h = nizhi(h);p3 = nizhi(p3);p1->next = p3;return h;
}