add reverse_inorder traversal to binary_tree_traversals.py (#8726)

* add reverse_inorder traversal to binary_tree_traversals.py

* Apply suggestions from code review

Co-authored-by: Tianyi Zheng <[email protected]>

---------

Co-authored-by: Tianyi Zheng <[email protected]>

Author: amirsoroush

data_structures/binary_tree/binary_tree_traversals.py

@@ -58,6 +58,19 @@ def inorder(root: Node | None) -> list[int]:
     return [*inorder(root.left), root.data, *inorder(root.right)] if root else []
 
 
+def reverse_inorder(root: Node | None) -> list[int]:
+    """
+    Reverse in-order traversal visits right subtree, root node, left subtree.
+    >>> reverse_inorder(make_tree())
+    [3, 1, 5, 2, 4]
+    """
+    return (
+        [*reverse_inorder(root.right), root.data, *reverse_inorder(root.left)]
+        if root
+        else []
+    )
+
+
 def height(root: Node | None) -> int:
     """
     Recursive function for calculating the height of the binary tree.
@@ -161,15 +174,12 @@ def zigzag(root: Node | None) -> Sequence[Node | None] | list[Any]:
 
 
 def main() -> None:  # Main function for testing.
-    """
-    Create binary tree.
-    """
+    # Create binary tree.
     root = make_tree()
-    """
-    All Traversals of the binary are as follows:
-    """
 
+    # All Traversals of the binary are as follows:
     print(f"In-order Traversal: {inorder(root)}")
+    print(f"Reverse In-order Traversal: {reverse_inorder(root)}")
     print(f"Pre-order Traversal: {preorder(root)}")
     print(f"Post-order Traversal: {postorder(root)}", "\n")