> ## 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.

# Minimum Depth of Binary Tree Python Solution

> Tested Python solution for LeetCode 111 with 20 pytest cases. Generate a practice environment with lcpy.

LeetCode 111, [Easy](/catalog/easy). Topics: [Tree](/catalog/topics/tree), [Depth-First Search](/catalog/topics/depth-first-search), [Breadth-First Search](/catalog/topics/breadth-first-search), [Binary Tree](/catalog/topics/binary-tree). [View on LeetCode](https://leetcode.com/problems/minimum-depth-of-binary-tree/description/).

Generate this problem as a practice environment: tested reference solution, 20 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 111   # by problem number
lcpy gen -s minimum_depth_of_binary_tree   # by problem name
```

## Problem

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

**Note:** A leaf is a node with no children.

### Examples

![Example 1](https://assets.leetcode.com/uploads/2020/10/12/ex_depth.jpg)

```
Input: root = [3,9,20,null,null,15,7]
Output: 2
```

```
Input: root = [2,null,3,null,4,null,5,null,6]
Output: 5
```

### Constraints

* The number of nodes in the tree is in the range `[0, 10^5]`.
* `-1000 <= Node.val <= 1000`

## Solution

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

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
from collections import deque

from leetcode_py import TreeNode


class Solution:
    # Time: O(n)
    # Space: O(w) where w is the maximum width of the tree
    def min_depth(self, root: TreeNode[int] | None) -> int:
        if root is None:
            return 0
        queue: deque[TreeNode[int]] = deque([root])
        depth = 1
        while queue:
            for _ in range(len(queue)):
                node = queue.popleft()
                if node.left is None and node.right is None:
                    return depth
                if node.left is not None:
                    queue.append(node.left)
                if node.right is not None:
                    queue.append(node.right)
            depth += 1
        return depth
```

## Complexity

| Time | Space                                         |
| ---- | --------------------------------------------- |
| O(n) | O(w) where w is the maximum width of the tree |

## Tags