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[(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.