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Diameter of Binary Tree

Problem statement​

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.

Example 1:

Input: root = [1,2,3,4,5]Output: 3Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].

Example 2:

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

Constraints:

  • The number of nodes in the tree is in the range [1, 104].
  • -100 <= Node.val <= 100

My solution​

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var diameterOfBinaryTree = function(root) {
    let maxPath = 0;
    
    function traverse(node) {
        if (!node) {
            return -1;
        }
        
        let left = traverse(node.left) + 1;
        let right = traverse(node.right) + 1;
        
        maxPath = Math.max(left + right, maxPath);
        
        return Math.max(left, right)
    }
    
    traverse(root)
    
    return maxPath;
};