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Maximum Depth of Binary Tree

Problem statement​

Given the root of a binary tree, return its maximum depth.

A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Example 1:

Input: root = [3,9,20,null,null,15,7]Output: 3

Example 2:

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

Constraints:

  • The number of nodes in the tree is in the range [0, 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 maxDepth = function(root) {
    function dfs(node, depth) {
        if (!node) {
            return depth;
        }
        
        return Math.max(dfs(node.left, depth + 1), dfs(node.right, depth + 1))
    }
    
    return dfs(root, 0);
};