ReveseList

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

For example:
Given1->2->3->4->5->NULL, m = 2 and n = 4,

return1->4->3->2->5->NULL.

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

package leetcode;

public class ReverseList {
public ListNode reverseBetween(ListNode head,int m,int n){
if(head==null)
return null;
ListNode helper=new ListNode(0);
helper.next=head;
ListNode pre=helper;
int i=1;
while(pre.next!=null&&i