Problem Reorder List

 1 public void reorderList(ListNode head) {
 2         int length = 0;
 3         ListNode p = head;
 4         List<ListNode> list = new ArrayList<ListNode>();
 5         while (p != null) {
 6             length++;
 7             list.add(p);
 8             p = p.next;
 9         }
10         int i = 0;
11         p = null;
12         while (i <= (length - 1 - i)) {
13             if (p != null) {
14                 p.next = list.get(i);
15             }
16             if (i != length -1 -i) {
17                 list.get(i).next = list.get(length - 1-i);
18                 p = list.get(length-1-i);
19                 p.next = null;
20             } else {
21                 list.get(i).next = null;
22             }
23 
24             i++;
25         }
26     }