In this post I will discuss the solution to the leetcode problem — Binary Tree Inorder Traversal.

## Problem:

Given the `root`

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

**Example 1:**

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

**Output:** [1,3,2]

**Example 2:**

**Input:** root = []

**Output:** []

**Example 3:**

**…**