diff --git a/notes-and-examples/2026.05.27/find_depth.py b/notes-and-examples/2026.05.27/find_depth.py
new file mode 100644
index 0000000..38f7fcb
--- /dev/null
+++ b/notes-and-examples/2026.05.27/find_depth.py
@@ -0,0 +1,36 @@
+# Tree example:
+#       10
+#      /  \
+#     5   15
+#    / \    \
+#   3   7   20
+
+
+class Node:
+    def __init__(self, value, left=None, right=None):
+        self.value = value
+        self.left: Node | None = left
+        self.right: Node | None = right
+
+
+root_node = Node(10)
+root_node.left = Node(5)
+root_node.left.left = Node(3)
+root_node.left.right = Node(7)
+root_node.right = Node(15)
+root_node.right.right = Node(20)
+
+
+def find_depth(root: Node | None, subtree_depth=0) -> int:
+    if root is None:
+        return subtree_depth
+
+    left_depth = find_depth(root.left, subtree_depth + 1)
+    right_depth = find_depth(root.right, subtree_depth + 1)
+    return max(left_depth, right_depth)
+
+
+print(find_depth(root_node))
+
+root_node.right.right.right = Node(1)
+print("After adding another level:", find_depth(root_node))
diff --git a/notes-and-examples/2026.05.27/homework.py b/notes-and-examples/2026.05.27/homework.py
new file mode 100644
index 0000000..d33d746
--- /dev/null
+++ b/notes-and-examples/2026.05.27/homework.py
@@ -0,0 +1 @@
+# Implement red-black rebalancing in code.
diff --git a/notes-and-examples/2026.05.27/invert_tree.py b/notes-and-examples/2026.05.27/invert_tree.py
new file mode 100644
index 0000000..884db8d
--- /dev/null
+++ b/notes-and-examples/2026.05.27/invert_tree.py
@@ -0,0 +1,40 @@
+# Tree example:
+#       10
+#      /  \
+#     5   15
+#    / \    \
+#   3   7   20
+
+
+class Node:
+    def __init__(self, value, left=None, right=None):
+        self.value = value
+        self.left: Node | None = left
+        self.right: Node | None = right
+
+
+root_node = Node(10)
+root_node.left = Node(5)
+root_node.left.left = Node(3)
+root_node.left.right = Node(7)
+root_node.right = Node(15)
+root_node.right.right = Node(20)
+
+
+def invert_tree(root: Node | None):
+    if root is None:
+        return
+
+    invert_tree(root.left)
+    invert_tree(root.right)
+
+    root.left, root.right = root.right, root.left
+
+
+invert_tree(root_node)
+
+print(root_node.left.value)
+print(root_node.right.value)
+print(root_node.left.left.value)
+print(root_node.right.right.value)
+print(root_node.right.left.value)