LeetCode刷题笔记（链表）：reverse-linked-list-ii

冷不防 2022-06-01 01:39 185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 ##

Reverse a linked list from position m to n. Do it in-place and in one-pass.

For example:  
Given1->2->3->4->5->NULL, m = 2 and n = 4,

return1->4->3->2->5->NULL.

Note:  
Given m, n satisfy the following condition:  
1 ≤ m ≤ n ≤ length of list.

## 解题思路 ##

可能是因为反转链表i太简单了，所以牛客网只有ii么，应该是这样的，哈哈哈。

头指针是必不可少的，因为有可能会要求全部反转。首先定位到需要反转的第一个元素，然后每次都将它后面的元素往它前面放。他们之间的关系大家最好自己画图捋一遍，这样记得比较清楚。

## 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 *reverseBetween(ListNode *head, int m, int n) {
            if(head == NULL)
                return NULL;
    
            int diff = n - m;
    
            ListNode *preHead = new ListNode(0);
            preHead->next = head;
            ListNode *preCur = preHead;
            ListNode *cur = head;
    
            for(int i = 1; i < m; ++i){
                preCur = cur;
                cur = cur->next;
            }
    
            for(int i = 0; i < diff; ++i){
                ListNode *tmp = cur->next;
                cur->next = tmp->next;
                tmp->next = preCur->next;
                preCur->next = tmp;
            }
            return preHead->next;
        }
    };

**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