Diameter of Binary Tree
Difficulty: Easy
Category: DSA
Topics: Tree, Depth-First Search, Binary Tree
Asked at: Facebook, Microsoft, Bloomberg, Amazon, Google, ByteDance, Oracle
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.
**Example 1:**
**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].
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**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`