16: 104. Maximum Depth of Binary Tree.py

# problem:
# https://leetcode.com/problems/maximum-depth-of-binary-tree/

# solution:
class Solution:
    def maxDepth(self, root: Optional[TreeNode]) -> int:
        if not root: return 0
        return 1+ max(self.maxDepth(root.left),self.maxDepth(root.right))