def _rotate_right(self, node):
assert_node(node)
assert_node(node.left)
if DEBUG:
print(f'# Rotating right {node}...')
parent = node.parent
new = node.left
# 1
if parent:
if node.is_left_child():
parent.left = new
else:
parent.right = new
new.parent = parent
else:
self.root = new
new.parent = None
# 2
node.left = new.right
if node.left:
node.left.parent = node
# 3
new.right = node
node.parent = new
def _rebalance_left(self, node):
assert_node(node)
if DEBUG:
print(f'# Rebalancing left {node}...')
middle = node.right
if middle.lheight > middle.rheight:
self._rotate_right(middle)
self._rotate_left(node)
node.recompute_height()
middle.recompute_height()
def _rebalance(self, node):
assert_node(node)
if DEBUG:
print(f'# Rebalancing {node}...')
parent = node.parent
if node.lheight > node.rheight + 1:
self._rebalance_right(node)
if node.rheight > node.lheight + 1:
self._rebalance_left(node)
node.recompute_height()
if parent:
self._rebalance(parent)