655 - Print Binary Tree\.

Medium

Given the root of a binary tree, construct a 0-indexed m x n string matrix res that represents a formatted layout of the tree. The formatted layout matrix should be constructed using the following rules:

• The height of the tree is height and the number of rows m should be equal to height + 1.

• The number of columns n should be equal to <code>2^height+1 - 1</code>.

• Place the root node in the middle of the top row (more formally, at location res[0][(n-1)/2]).

• For each node that has been placed in the matrix at position res[r][c], place its left child at <code>resc-2^height-r-1</code> and its right child at <code>resc+2^height-r-1</code>.

• Continue this process until all the nodes in the tree have been placed.

• Any empty cells should contain the empty string "".

Return the constructed matrix res.

Example 1:

Input: root = 1,2

Output:

[["","1",""],
 ["2","",""]]

Example 2:

Input: root = 1,2,3,null,4

Output:

[["","","","1","","",""],
 ["","2","","","","3",""],
 ["","","4","","","",""]]

Constraints:

• The number of nodes in the tree is in the range <code>1, 2¹⁰</code>.

• -99 <= Node.val <= 99

• The depth of the tree will be in the range [1, 10].