Leetcode 92 反转链表 II C++

思路：参考http://www.cnblogs.com/grandyang/p/4306611.html
暴力法，一步步向后反转即可。

/**
 * 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) {
                ListNode *dummy = new ListNode(-1), *pre = dummy;
        dummy->next = head;
        for (int i = 0; i < m - 1; ++i) pre = pre->next;
        ListNode *cur = pre->next;
        for (int i = m; i < n; ++i) {
            ListNode *t = cur->next;
            cur->next = t->next;
            t->next = pre->next;
            pre->next = t;
        }
        return dummy->next;
 
        
    }
};