题解 | #删除链表的倒数第n个节点#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 * };
 */

class Solution {
  public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        // write code here
        if (head == nullptr) return nullptr;
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* f = head;
        ListNode* s = head;
        ListNode* pre = dummy;
        for (int i = 0; i < n; i++) {
            if (f != nullptr) {
                f = f->next;
            } else {
                return nullptr;
            }
        }
        while (f != nullptr) {
            pre = s;
            s = s->next;
            f = f->next;
        }
        pre->next = s->next;
        return dummy->next;
    }
};