def rotate_right(self, old_root: BinaryTreeNode):
new_root = old_root.left
# 1.change upper relationships.
if old_root.is_root():
self.set_root(new_root)
else:
old_root.parent.set_child(new_root)
# 2.change old_root's left
old_root.set_left(new_root.right)
# 3.change new root's right
new_root.set_right(old_root)
# 4.update color
new_root.color = old_root.color
old_root.color = RED
# 5.update size
old_root.update_size()
new_root.update_size()
return new_root
def flip_colors(self, node: BinaryTreeNode):
if self.is_red(node.left) and self.is_red(node.right):
node.left.color = BLACK
node.right.color = BLACK
if not node.is_root():
node.color = RED
