---
tags: data_structure_python
---

# Maximum Depth of Binary Tree <img src="https://img.shields.io/badge/-easy-brightgreen">

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

**Note**: A leaf is a node with no children.

<ins>**Example:**</ins>

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its depth = 3.

## Solution

# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        if root is None:
            return 0
        else:
            return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))