Diameter of Binary Tree

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 is measured by the number of edges between nodes.

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Example 1:

    1
   / \
  2   3
 / \
4   5

Input: root = [1,2,3,4,5]
Output: 3
Explanation: The path 4 -> 2 -> 1 -> 3 or 5 -> 2 -> 1 -> 3 has 3 edges.

Example 2:

Input: root = [1,2]
Output: 1
Explanation: The only path is 1 -> 2, which has 1 edge.

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Constraints

• The number of nodes in the tree is in the range [1, 10^4].
• -100 <= Node.val <= 100