143. 重排链表

public class Solution {
    public void reorderList(ListNode head) {
        if (head == null) {
            return;
        }
        List<ListNode> array = new ArrayList<>();
        ListNode node = head;
        while (node != null) {
            array.add(node);
            node = node.next;
        }
        int left = 0;
        int right = array.size() - 1;
        while (left < right) {
            array.get(left).next = array.get(right);
            left++;
            if(left == right){
                break;
            }
            array.get(right).next = array.get(left);
            right--;
        }
        array.get(left).next = null;
    }
}