leetcode/tree/inorder_transversal.py

from typing import Optional, List
from tree import TreeNode

class Solution:
    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
        if root == None:
            return []
        left = self.inorderTraversal(root.left)
        right = self.inorderTraversal(root.right)
        return left + [root.val] + right