0655. Print Binary Tree

https://leetcode.com/problems/print-binary-tree

Description

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].

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