代码实现：

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* removeNthFromEnd(struct ListNode *head, int n) {
    if (head == NULL || n == 0) {
        return head;
    }
    int i = n;
    struct ListNode *h = malloc(sizeof(*h));
    h->next = head;
    struct ListNode *p = h;
    struct ListNode *pp = head;
    while (i--) {
        pp = pp->next;
    }
    while (pp) {
        pp = pp->next;
        p = p->next;
    }
    struct ListNode *pc = p->next;
    p->next = pc->next;
    pc->next = NULL;

    free(pc);
    return h->next;
}