题目：

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.

1     public ListNode reverseBetween(ListNode head, int m, int n) { 2         if(head == null) return null; 3         ListNode dummy = new ListNode(0); 4         dummy.next = head; 5         ListNode pre = dummy; 6         ListNode start = head; 7          8         for (int i = 1; i < m; i++) { 9             start = start.next;10             pre = pre.next;11         }12         ListNode end = start;13         ListNode then = start.next;14         ListNode temp = then;15         for (int j = 0; j < n - m;  j++) {16             temp = then.next;17             then.next = start;18             start = then;19             then = temp;20         }21         pre.next = start;22         end.next = then;23         return dummy.next;24     }

感觉写的挺丑的。。。