LeetCode刷题笔记（链表）：remove-nth-node-from-end-of-list

青旅半醒 2022-06-01 05:46 80阅读 0赞

--------------------

*  **转载请注明作者和出处：[http://blog.csdn.net/u011475210][http_blog.csdn.net_u011475210]**
 *  **代码地址：[https://github.com/WordZzzz/Note/tree/master/LeetCode][https_github.com_WordZzzz_Note_tree_master_LeetCode]**
 *  **刷题平台：[https://www.nowcoder.com/ta/leetcode][https_www.nowcoder.com_ta_leetcode]**
 *  **题  库：Leetcode经典编程题**
 *  **编  者：WordZzzz**

--------------------

*   *  题目描述
     *  解题思路
     *  C版代码实现

## 题目描述 ##

Given a linked list, remove the n th node from the end of list and return its head.

For example,

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.  
Note:  
Given n will always be valid.  
Try to do this in one pass.

## 解题思路 ##

删除倒数第n个结点，我们就需要找到倒数第n个结点。于是，我们可以利用快慢指针来实现。

首先，fast走n步指向第n个结点；接着，fast和slow一起走，直到fast指向尾结点；最后，删除元素（这里需要注意的是加入pre来判断删除元素是否为头结点）。

## C++版代码实现 ##

/**
     * Definition for singly-linked list.
     * struct ListNode {
     *     int val;
     *     ListNode *next;
     *     ListNode(int x) : val(x), next(NULL) {}
     * };
     */
    class Solution {
    public:
        ListNode *removeNthFromEnd(ListNode *head, int n) {
            if(head == NULL)
                return NULL;
    
            ListNode *slow = head;
            ListNode *fast = head;
            ListNode *pre = NULL;
            //fast先走n步，到达第n个结点
            while(--n)
                fast = fast->next;
            //fast和slow一起走，直到fast走到链表尾部
            while(fast->next != NULL){
                pre = slow;
                slow = slow->next;
                fast = fast->next;
            }
            //此处用于判断删除的结点是否为头结点
            if(pre != NULL)
                pre->next = slow->next;
            else
                head = head->next;
    
            return head;
        }
    };

**系列教程持续发布中，欢迎订阅、关注、收藏、评论、点赞哦～～(￣▽￣～)～**

**完的汪(∪｡∪)｡｡｡zzz**

[http_blog.csdn.net_u011475210]: http://blog.csdn.net/u011475210
[https_github.com_WordZzzz_Note_tree_master_LeetCode]: https://github.com/WordZzzz/Note/tree/master/LeetCode
[https_www.nowcoder.com_ta_leetcode]: https://www.nowcoder.com/ta/leetcode