Given the root of a binary tree, return an array of the largest value in each row of the tree (0-indexed).
Example 1:
Input: root = [1, 3, 2, 5, 3, null, 9]
Output: [1, 3, 9]
Explanation:
Example 2:
Input: root = [1, 2, 3]
Output: [1, 3]
Example 3:
Input: root = []
Output: []
[0, 10⁴]-2³¹ <= Node.val <= 2³¹ - 1