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;
}