Overview

Given the root of a binary tree, return the diameter — the length of the longest path between any two nodes. The path may or may not pass through the root. Length is measured in number of edges.

Constraints

• The number of nodes is in the range [1, 10,000].
• -100 <= Node.val <= 100

Examples

diameterOfBinaryTree([1, 2, 3, 4, 5]);
// => 3  (path: 4 → 2 → 1 → 3)

diameterOfBinaryTree([1, 2]);
// => 1

Solution

function diameterOfBinaryTree(root) {
  let diameter = 0;
  function depth(node) {
    if (!node) return 0;
    const left = depth(node.left);
    const right = depth(node.right);
    diameter = Math.max(diameter, left + right);
    return Math.max(left, right) + 1;
  }
  depth(root);
  return diameter;
}

Resources

• Diameter of Binary Tree — LeetCode