链表四：删除倒数第n个结点

题目地址： https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/

题目描述： 给你一个链表，删除链表的倒数第 n 个结点，并且返回链表的头结点。

参考代码：

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* visualH = new ListNode();
        visualH->next = head;
        ListNode* fast = visualH;
        ListNode* slow = visualH;
        while (n-- && fast) {
            fast = fast->next;
        }
        if (fast == nullptr) {
            return  head;
        }
        while (fast->next) { // 查询删除节点的上个节点
            fast = fast->next;
            slow = slow->next;
        }
        ListNode *tmp = slow->next;
        slow->next = slow->next->next;
        delete tmp;
        return visualH->next;

    }
};

参考链接： https://github.com/youngyangyang04/leetcode-master/blob/master/problems/0019.%E5%88%A0%E9%99%A4%E9%93%BE%E8%A1%A8%E7%9A%84%E5%80%92%E6%95%B0%E7%AC%ACN%E4%B8%AA%E8%8A%82%E7%82%B9.md