> ## 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.

# Binary Tree Inorder Traversal Python Solution

> Tested Python solution for LeetCode 94 with 15 pytest cases. Generate a practice environment with lcpy.

LeetCode 94, Easy. Topics: Stack, Tree, Depth-First Search, Binary Tree. [View on LeetCode](https://leetcode.com/problems/binary-tree-inorder-traversal/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 94   # by problem number
lcpy gen -s binary_tree_inorder_traversal   # by problem name
```

## Problem

Given the `root` of a binary tree, return the inorder traversal of its nodes' values.

### Examples

![Example 1](https://assets.leetcode.com/uploads/2024/08/29/screenshot-2024-08-29-202743.png)

```
Input: root = [1,null,2,3]
Output: [1,3,2]
```

![Example 2](https://assets.leetcode.com/uploads/2024/08/29/tree_2.png)

```
Input: root = [1,2,3,4,5,null,8,null,null,6,7,9]
Output: [4,2,6,5,7,1,3,9,8]
```

```
Input: root = []
Output: []
```

```
Input: root = [1]
Output: [1]
```

### Constraints

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

**Follow up:** Recursive solution is trivial, could you do it iteratively?

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/binary_tree_inorder_traversal/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/binary_tree_inorder_traversal/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) where h is the height of the tree
    def inorder_traversal(self, root: TreeNode[int] | None) -> list[int]:
        result: list[int] = []
        stack: list[TreeNode[int]] = []
        current: TreeNode[int] | None = root

        while current or stack:
            while current:
                stack.append(current)
                current = current.left

            current = stack.pop()
            result.append(current.val)
            current = current.right

        return result
```

## Complexity

| Time | Space                                  |
| ---- | -------------------------------------- |
| O(n) | O(h) where h is the height of the tree |

## Tags

[NeetCode 250](/catalog/neetcode-250), [NeetCode All](/catalog/neetcode), [AlgoMaster 75](/catalog/algo-master-75).