1 public class Solution {
 2     public List<List<String>> printTree(TreeNode root) {
 3         int height = getHeight(root);
 4         String[][] res = new String[height][(1 << height) - 1];
 5         for(String[] arr:res)
 6             Arrays.fill(arr,"");
 7         List<List<String>> ans = new ArrayList<>();
 8         fill(res, root, 0, 0, res[0].length);
 9         for(String[] arr:res)
10             ans.add(Arrays.asList(arr));
11         return ans;
12     }
13     public void fill(String[][] res, TreeNode root, int i, int l, int r) {
14         if (root == null)
15             return;
16         res[i][(l + r) / 2] = "" + root.val;
17         fill(res, root.left, i + 1, l, (l + r) / 2);
18         fill(res, root.right, i + 1, (l + r + 1) / 2, r);
19     }
20     public int getHeight(TreeNode root) {
21         if (root == null)
22             return 0;
23         return 1 + Math.max(getHeight(root.left), getHeight(root.right));
24     }
25 }