1  public List<List<String>> printTree(TreeNode root) {

 2         ArrayList<List<String>> al = new ArrayList<>();

 3         if (root == null) return al;

 4         if (root.left == null && root.right == null) {

 5             al.add(new ArrayList<>());

 6             al.get(0).add(String.valueOf(root.val));

 7             return al;

 8         }

 9

10         int high = dep(root, 1);

11         String[][] ans = new String[(int) Math.pow(2, high)][high + 1];

12         add(root, (int) Math.pow(2, high - 1), 1, (int) Math.pow(2, high - 2), ans);

13         for (int i = 1; i <= high; i++) {

14             al.add(new ArrayList<>());

15             for (int j = 1; j < ans.length; j++)

16                 al.get(i - 1).add(ans[j][i] == null ? "" : ans[j][i]);

17         }

18         return al;

19     }

20

21     public void add(TreeNode cur, int x, int y, int diff, String[][] ans) {

22         if (cur == null) return;

23         ans[x][y] = cur.val + "";

24         add(cur.left, x - diff, y + 1, diff / 2, ans);

25         add(cur.right, x + diff, y + 1, diff / 2, ans);

26     }

27

28

29     public int dep(TreeNode cur, int dep) {

30         if (cur == null) return dep - 1;

31         return Math.max(dep(cur.left, dep + 1), dep(cur.right, dep + 1));

32     }