/**

* 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) {

// Start typing your C/C++ solution below

// DO NOT write int main() function

ListNode prev_head(0);

prev_head.next = head;

ListNode *prev = &prev_head;

ListNode *current = head;

for (int i = 0; i < m - 1; i++) {

prev = prev->next;

current = current->next;

}

ListNode *end = current;

for (int i = m - 1; i < n; i++) {

ListNode *next = current->next;

current->next = prev->next;

prev->next = current;

current = next;

}

end->next = current;

return prev_head.next;

}

};