public class Solution
extends Object
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 2height+1 - 1.
* 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 res[r+1][c-2height-r-1] and its **right child** at res[r+1][c+2height-r-1].
* 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 [1, 210].
* `-99 <= Node.val <= 99`
* The depth of the tree will be in the range `[1, 10]`.