Solve 94. Binary Tree Inorder Traversal

python/94_binary_tree_inorder_traversal.py

@@ -0,0 +1,14 @@
+# 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
+class Solution:
+    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        def inorderInner(root: Optional[TreeNode], out: List[int]):
+            if root is None: return out
+            inorderInner(root.left, out)
+            out.append(root.val)
+            return inorderInner(root.right, out)
+        return inorderInner(root, [])