Reverse Linked List II

没什么好说的，搞清楚关系就好。

/**
* 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 || head->next == NULL)
return head;
int index = 1;
ListNode *fake = new ListNode(-1);
fake->next = head;
ListNode *last = fake;
ListNode *p = head;
while (index < m) {
last = p;
p = p->next;
index++;
}
ListNode *pre = NULL;
while (index <= n) {
ListNode *p_next = p->next;
p->next = pre;
pre = p;
p = p_next;
index++;
}
last->next->next = p;
last->next = pre;
return fake->next;
}
};
http://oj.leetcode.com/problems/reverse-linked-list-ii/