Diameter of a Binary Tree Problem Statement

Given a binary tree, return the length of its diameter. The diameter of a binary tree is defined as the length of the longest path between any two nodes in the tree.

Example:

Input:

The tree is represented in level order by node values, using '-1' to denote null nodes. Example input tree: 
1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1

Output:

6

Explanation:

The path with the maximum length is formed by the nodes highlighted in the image of the tree, resulting in a diameter of 6 edges.

Constraints:

• 1 <= T <= 10: Number of test cases.
• 0 <= N <= 10^5: Total number of nodes in the binary tree.
• 1 <= data <= 10^4: Value of a binary tree node.
• Time Limit: 1 second.

Note:

The input for each test case will be a sequence of node values arranged in level-order traversal, with '-1' used for null and placeholder nodes.