104-Maximum-Depth-of-Binary-Tree.py

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

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