LeetCode:Reverse LinkedListⅡ

Problem:

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

For example:
Given 1->2->3->4->5->NULL, m = 2 and n = 4,

return 1->4->3->2->5->NULL.

Note:
Given m, n satisfy the following condition:
1 ≤ m ≤ n ≤ length of list.

Solution:逆转用的头插法

/**
 * 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 result(-1);
        result.next=head;

        ListNode *prev=&result;

        for(int i=0;i<m-1;i++)
            prev=prev->next;

        ListNode *head2=prev;

        prev=head2->next;
        ListNode *cur=prev->next;
        for(int i=m;i<n;i++)
        {
            prev->next=cur->next;
            cur->next=head2->next;
            head2->next=cur;  //头插法
            cur=prev->next;
        }

       return result.next;

    }
};