leetcode--Reorder List

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}.

/**
 * Definition for singly-linked list.
 * class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public void reorderList(ListNode head) {
        if(head != null){
            ListNode stepOne = head, stepTwo = head;
            while(stepTwo.next != null){
                if(stepTwo.next != null)
                    stepTwo = stepTwo.next;
                if(stepTwo.next != null){
                    stepTwo = stepTwo.next;
                    stepOne = stepOne.next;
                }
            }
            if(stepOne.next != null){
                stepTwo = stepOne.next;
                stepOne.next = null;
                ListNode tailOfSecond = stepTwo;
                stepOne = stepTwo;
                if(stepTwo.next != null)
                    stepTwo = stepTwo.next;
                while(stepTwo.next != null){
                    ListNode temp = stepTwo.next;
                    stepTwo.next = stepOne;
                    stepOne = stepTwo;
                    stepTwo = temp;
                }
                stepTwo.next = stepOne;
                tailOfSecond.next = null;
            }

            stepOne = head;
            if(stepTwo != stepOne){
                while(stepTwo != null){
                    ListNode temp = stepOne.next;
                    stepOne.next = stepTwo;
                    stepOne = stepOne.next;
                    stepTwo = temp;
                }
            }
        }        
    }
}