LeetCode-in-All

104. Maximum Depth of Binary Tree

Easy

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:

Solution

# Definition for a binary tree node.
#
# defmodule TreeNode do
#   @type t :: %__MODULE__{
#           val: integer,
#           left: TreeNode.t() | nil,
#           right: TreeNode.t() | nil
#         }
#   defstruct val: 0, left: nil, right: nil
# end

defmodule Solution do
  @spec max_depth(root :: TreeNode.t() | nil) :: integer
  def max_depth(nil), do: 0

  def max_depth(root) do
    max(max_depth(root.left), max_depth(root.right)) + 1
  end
end