package leetcode._92_;

import leetcode.common.ListNode;

/**

* Definition for singly-linked list.

* public class ListNode {

* int val;

* ListNode next;

* ListNode(int x) { val = x; }

* }

*/

class Solution {

public ListNode reverseBetween(ListNode head, int m, int n) {

ListNode fakeNode = new ListNode(-1);

fakeNode.next = head;

ListNode p = fakeNode;

ListNode q = head;

int index = 1;

while (q.next != null) {

if (index >= m && index < n) {

ListNode node = q.next;

q.next = q.next.next;

node.next = p.next;

p.next = node;

} else {

q = q.next;

}

if (index < m) {

p = p.next;

}

if (++index >= n) {

break;

}

}

return fakeNode.next;

}

}