Method maxDepth

Python/maximum-depth-of-binary-tree.py:13–17

(self, root: TreeNode)

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