# 543. Diameter of Binary Tree

## Easy

***

Given the `root` of a binary tree, return _the length of the **diameter** of the tree_.

The **diameter** of a binary tree is the **length** of the longest path between any two nodes in a tree. This path may or may not pass through the `root`.

The **length** of a path between two nodes is represented by the number of edges between them.

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**Example 1:**

![](https://assets.leetcode.com/uploads/2021/03/06/diamtree.jpg)

```
Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].
```

**Example 2:**

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

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**Constraints:**

* The number of nodes in the tree is in the range `[1, 104]`.
* `-100 <= Node.val <= 100`
