# [Solved] 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. ## Question

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`

## Python Solution

```# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
mx = 0
def find_max(root,level):
global mx
if root==None:return
mx = max(mx,level)
find_max(root.left,level+1)
find_max(root.right,level+1)

class Solution:
def maxDepth(self, root: TreeNode) -> int:
global mx
mx = 0
find_max(root,1)
return mx```
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