题解 | #删除链表的倒数第n个节点#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类
     * @param n int整型
     * @return ListNode类
     */
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* res = head;
        ListNode* fast = head;
        ListNode* slow = head;

        for (int i = 0; i < n; i++) {
            fast = fast->next;
        }

        while (fast != nullptr) {
            fast = fast->next;
            slow = slow->next;
        }

        fast = head;
        if (fast == slow) return res->next;
        else {
            while (fast->next != slow) {
                fast = fast->next;
            }

            fast->next = slow->next;
            return res;
        }
    }
};