0104: 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

Code Solution

class Solution:
    def maxDepth(self, root):
        def rec(node):
            if not node:
                return 0
            return 1 + max(rec(node.left), rec(node.right))
        return rec(root) if root else 0