> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# Maximum Depth of Binary Tree Python Solution

> Tested Python solution for LeetCode 104 with 15 pytest cases. Generate a practice environment with lcpy.

LeetCode 104, Easy. Topics: Tree, Depth-First Search, Breadth-First Search, Binary Tree. [View on LeetCode](https://leetcode.com/problems/maximum-depth-of-binary-tree/description/).

Generate this problem as a practice environment: tested reference solution, 15 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 104   # by problem number
lcpy gen -s maximum_depth_of_binary_tree   # by problem name
```

## Problem

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

A binary tree's **maximum depth** is the number of nodes along the longest path from the root node down to the farthest leaf node.

### Examples

![Example 1](https://assets.leetcode.com/uploads/2020/11/26/tmp-tree.jpg)

```
Input: root = [3,9,20,null,null,15,7]
Output: 3
```

```
Input: root = [1,null,2]
Output: 2
```

### Constraints

* The number of nodes in the tree is in the range `[0, 10^4]`.
* `-100 <= Node.val <= 100`

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/maximum_depth_of_binary_tree/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/maximum_depth_of_binary_tree/test_solution.py):

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
from leetcode_py import TreeNode


class Solution:
    # Time: O(n)
    # Space: O(h)
    def max_depth(self, root: TreeNode[int] | None) -> int:
        if not root:
            return 0

        left_depth = self.max_depth(root.left)
        right_depth = self.max_depth(root.right)

        return 1 + max(left_depth, right_depth)
```

## Complexity

| Time | Space |
| ---- | ----- |
| O(n) | O(h)  |

## Tags

[Grind 75](/catalog/grind-75), [Grind](/catalog/grind), [Blind 75](/catalog/blind-75), [NeetCode 150](/catalog/neetcode-150), [NeetCode 250](/catalog/neetcode-250), [NeetCode All](/catalog/neetcode).