Leetcode#92 Reverse Linked List II

第一步，找到将要翻转的位置，记录翻转部分前一个节点(prev)

第二步，翻转，记录翻转完成后这部分的首(reverseHead)和尾(reverseTail)，以及翻转部分之后的一个节点(post)

第三部，将prev、reverseHead、reverseTail、post连接起来

代码：

 1 ListNode *reverseBetween(ListNode *head, int m, int n) {
 2         ListNode *node = head;
 3         ListNode *prev = NULL;
 4         ListNode *post = NULL;
 5         ListNode *reverseHead = NULL;
 6         ListNode *reverseTail = NULL;
 7         int count = 1;
 8         
 9         if (!head)
10             return NULL;
11         
12         prev = NULL;
13         while (node && count < m ) {
14             prev = node;
15             node = node->next;
16             count++;
17         }
18         
19         if (!node)
20             return head;
21         
22         reverseTail = node;
23         post = node->next;
24         while (post && count < n) {
25             ListNode *postNext = post->next;
26             post->next = node;
27             node = post;
28             post = postNext;
29             count++;
30         }
31         reverseHead = node;
32         reverseTail->next = post;
33         
34         if (!prev)
35             return reverseHead;
36         else {
37             prev->next = reverseHead;
38             return head;
39         }
40 }