92. Reverse Linked List II

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

Note: 1 ≤ m ≤ n ≤ length of list.

Input: 1->2->3->4->5->NULL, m = 2, n = 4
Output: 1->4->3->2->5->NULL

翻转指定范围内的节点。

解决：用一个i记录当前是第几号节点。

 1 class Solution {
 2 public:
 3     ListNode* reverseBetween(ListNode* head, int m, int n) {
 4         int i = 1;
 5         ListNode* myhead = new ListNode(0);
 6         myhead->next = head;
 7         ListNode* pre = myhead;
 8         ListNode* curr = myhead->next;
 9         while (curr->next) {
10             if (i < m || i >= n) {
11                 pre = pre->next;
12                 curr = curr->next;
13                 ++i;
14             }
15             else {
16                 ListNode* temp = pre->next;
17                 pre->next = curr->next;
18                 curr->next = curr->next->next;
19                 pre->next->next = temp;
20                 ++i;
21             }
22         }
23         ListNode* temp = myhead->next;
24         delete myhead;
25         return temp;
26     }
27 };

 

posted @ 2018-04-23 11:38  Zzz...y  阅读(169)  评论(0)  编辑  收藏  举报