Neetcode: Maximum Depth of Binary Tree

Instructions

Given the root of a binary tree, return its depth.

The depth of a binary tree is defined as the number of nodes along the longest path from the root node down to the farthest leaf node.

Example 1:

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

Output: 3

Example 2:

Input: root = []

Output: 0

Constraints:

• 0 <= The number of nodes in the tree <= 100
• -100 <= Node.val <= 100