Diameter of Binary Tree

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 the 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.

Examples

Example 1:

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

        1
       / \
      2   3
     / \
    4   5

Example 2:

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

Constraints

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

Expected Complexity

• Time: O(n)
• Space: O(h) where h is the height of the tree