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 between two nodes is represented by the number of edges between them. ### Constraints - The number of nodes in the tree is in the range `[1, 10^4]`. - `-100 <= Node.val <= 100` ### Input Format A single line containing space-separated integers representing the tree in level-order (-1 for null). ### Output Format Print a single integer representing the diameter of the tree.