[LeetCode] Reverse Linked List II

weixin_34364071

于 2015-09-01 23:55:00 发布

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文章标签：开发工具

原文链接：https://yq.aliyun.com/articles/331366

本文介绍了一种反转链表中[m, n]区间内节点的方法。首先创建一个指向头节点的新节点new_head，并通过它找到待反转区间的前一个节点pre。接着将cur设置为pre的下一个节点，并依次将cur后面的节点move移动到pre后面，重复此过程n-m次，最终返回反转后的链表。

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The basic idea is as follows:

Create a new_head that points to head and use it to locate the immediate node before them-th (notice that it is 1-indexed) node pre;
Set cur to be the immediate node after pre and at each time move the immediate node after cur (named move) to be the immediate node after pre. Repeat it for n - m times.

 1 class Solution {  
 2 public:
 3     ListNode* reverseBetween(ListNode* head, int m, int n) {
 4         ListNode* new_head = new ListNode(0);
 5         new_head -> next = head;
 6         ListNode* pre = new_head;
 7         for (int i = 0; i < m - 1; i++)
 8             pre = pre -> next;
 9         ListNode* cur = pre -> next;
10         for (int i = 0; i < n - m; i++) {
11             ListNode* move = cur -> next; 
12             cur -> next = move -> next;
13             move -> next = pre -> next;
14             pre -> next = move;
15         }
16         return new_head -> next;
17     }
18 };