Matej Focko
e28f578fc2
Move rotations to the RankedTree, which allows us to factor out the functionality regarding rotations when root of the tree changes. Signed-off-by: Matej Focko <mfocko@redhat.com>
137 lines
3.5 KiB
Python
137 lines
3.5 KiB
Python
from ranked_tree import RotateFunction
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from avl import AVLTree
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from node import Node, NodeType, Comparable
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import logging
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from typing import TypeVar, Optional
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logger = logging.getLogger(__name__)
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T = TypeVar("T", bound=Comparable)
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class WAVLTree(AVLTree[T]):
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def is_correct_node(
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self, node: Optional[Node[T]], recursive: bool = True
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) -> bool:
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if not node:
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return True
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for child_rank in Node.differences(node):
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if child_rank not in (1, 2):
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return False
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if node.type == NodeType.LEAF:
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return node.rank == 0
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return not recursive or (
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self.is_correct_node(node.left)
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and self.is_correct_node(node.right)
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)
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# region DeleteRebalance
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def __fix_delete(
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self,
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x: Optional[Node[T]],
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y: Node[T],
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z: Node[T],
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reversed: bool,
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rotate_left: RotateFunction[T],
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rotate_right: RotateFunction[T],
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) -> None:
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v = y.left
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w = y.right
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if reversed:
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v, w = w, v
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w_diff = Node.difference(w, y)
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if w_diff == 1 and y.parent:
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rotate_left(y.parent)
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y.promote()
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z.demote()
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if z.type == NodeType.LEAF:
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z.demote()
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elif w_diff == 2 and v.parent:
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rotate_right(v.parent)
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rotate_left(v.parent)
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v.promote().promote()
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y.demote()
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z.demote().demote()
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def __bottomup_delete(
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self, x: Optional[Node[T]], parent: Optional[Node[T]]
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) -> None:
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x_diff = Node.difference(x, parent)
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if x_diff != 3 or not parent:
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return
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y = parent.right if parent.left is x else parent.left
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y_diff = Node.difference(y, parent)
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while (
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parent
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and x_diff == 3
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and y
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and (y_diff == 2 or Node.differences(y) == (2, 2))
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):
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if y_diff != 2:
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y.demote()
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parent.demote()
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x = parent
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parent = x.parent
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if not parent:
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return
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y = parent.right if parent.left is x else parent.left
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x_diff = Node.difference(x, parent)
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y_diff = Node.difference(y, parent)
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parent_node_diffs = Node.differences(parent)
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if parent_node_diffs in ((1, 3), (3, 1)):
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if parent.left is x:
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assert parent.right
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self.__fix_delete(
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x,
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parent.right,
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parent,
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False,
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self.rotate_left,
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self.rotate_right,
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)
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else:
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assert parent.left
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self.__fix_delete(
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x,
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parent.left,
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parent,
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True,
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self.rotate_right,
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self.rotate_left,
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)
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def _delete_rebalance(
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self, y: Optional[Node[T]], parent: Optional[Node[T]]
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) -> None:
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if Node.differences(y) == (2, 2):
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y.demote()
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parent = y.parent
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elif Node.differences(parent) == (2, 2):
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parent.demote()
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parent = parent.parent
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if not parent:
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return
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for y in (parent.left, parent.right):
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if Node.difference(y, parent) == 3:
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self.__bottomup_delete(y, parent)
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return
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# endregion DeleteRebalance
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