Reorder List (LeetCode Linked List)

Question: Given a singly linked list L: L0→L1→…→Ln-1→Ln,
reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…
You must do this in-place without altering the nodes' values.
For example,
Given {1,2,3,4}, reorder it to {1,4,2,3}.

Idea: First split the linked list to two half at point Ln/2. Then reverse the second half. Then we have a list like this:
L0 -> L1 ->... ->Ln/2-> Ln/2+1 <-Ln/2+2... <-Ln, where Ln/2+1.next=null. Then we merge the list from the two ends L0 and Ln one by one, e.g. L0 -> Ln -> L1 -> Ln-1 -> ... -> Ln/2 -> Ln/2+1.

Time: O(n) Space: O(n) (since the reverse of the second half is recursion which needs a O(n) stack).

Code: 

 public class Solution {  
   public ListNode reverseList(ListNode head)  
   {  
     if(head==null||head.next==null)  
       return head;  
     reverseList(head.next).next=head;  
     head.next=null;  
     return head;  
   }  
   public void reorderList(ListNode head) {  
     if(head==null||head.next==null)  
       return;  
     ListNode slower=head;  
     ListNode faster=head;  
     while(faster.next!=null)  
     {  
       faster=faster.next;  
       slower=slower.next;  
       if(faster.next!=null)  
         faster=faster.next;  
     }  
     reverseList(slower);  
     ListNode cur=head;  
     while(faster!=slower)  
     {  
       ListNode fasterTmp=faster.next;  
       faster.next=cur.next;  
       cur.next=faster;  
       faster=fasterTmp;  
       cur=cur.next.next;  
     }  
   }  
 }