.gitlab-ci.yml

@@ -1,42 +0,0 @@
-image: python:latest
-
-variables:
-  PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
-
-cache:
-  paths:
-    - .cache/pip
-    - venv/
-
-before_script:
-  - python --version
-  - pip install virtualenv
-  - virtualenv venv
-  - source venv/bin/activate
-
-black:
-  stage: test
-  script:
-    - pip install black
-    - make black
-
-flake8:
-  stage: test
-  script:
-    - pip install flake8
-    - make flake8
-
-pytest:
-  stage: test
-  script:
-    - pip install hypothesis pytest pytest-cov
-    - make check
-  coverage: '/TOTAL.*\s([.\d]+)%/'
-  artifacts:
-    when: always
-    reports:
-      junit: report.xml
-      coverage_report:
-        coverage_format: cobertura
-        path: coverage.xml
-

Makefile

@@ -1,5 +1,5 @@
 check:
-	pytest -vvv --log-level debug --cov --cov-report=term-missing --cov-report=xml:coverage.xml --junitxml=report.xml
+	pytest -vvv --log-level debug --cov --cov-report=term-missing
 
 lint: black flake8 mypy
 
@@ -10,7 +10,7 @@ flake8:
 	flake8 *.py
 
 mypy:
-	mypy --strict --disallow-any-explicit node.py ranked_tree.py avl.py wavl.py ravl.py rbt.py
+	mypy --strict --disallow-any-explicit node.py avl.py wavl.py ravl.py
 
 clean:
 	rm -rf __pycache__ .hypothesis .mypy_cache .pytest_cache

avl.py

@@ -1,5 +1,5 @@
-from node import Node, Comparable
+from node import Node, Comparable, RotateFunction
-from ranked_tree import RankedTree, RotateFunction
+from ranked_tree import RankedTree
 
 import logging
 from typing import TypeVar, Optional
@@ -49,18 +49,22 @@ class AVLTree(RankedTree[T]):
         z: Node[T],
         rotate_left: RotateFunction[T],
         rotate_right: RotateFunction[T],
-    ) -> None:
+    ) -> Optional[Node[T]]:
+        new_root = x.parent
+
         if not y or Node.difference(y) == 2:
-            rotate_right(z)
+            new_root = rotate_right(z)
             z.demote()
         elif Node.difference(y) == 1:
             rotate_left(x)
-            rotate_right(z)
+            new_root = rotate_right(z)
 
             y.promote()
             x.demote()
             z.demote()
 
+        return new_root
+
     def _insert_rebalance(self, x: Node[T]) -> None:
         diffs = Node.differences(x.parent)
         while x.parent and (diffs == (0, 1) or diffs == (1, 0)):
@@ -72,6 +76,9 @@ class AVLTree(RankedTree[T]):
         if not x.parent:
             return
 
+        rotating_around_root = x.parent.parent is None
+        new_root: Optional[Node[T]] = x.parent
+
         rank_difference = Node.difference(x)
         if rank_difference != 0:
             return
@@ -79,14 +86,17 @@ class AVLTree(RankedTree[T]):
         x_parent = x.parent
         assert x_parent is not None
         if rank_difference == 0 and x.parent.left is x:
-            self.__fix_0_child(
+            new_root = self.__fix_0_child(
-                x, x.right, x_parent, self.rotate_left, self.rotate_right
+                x, x.right, x_parent, Node.rotate_left, Node.rotate_right
             )
         elif rank_difference == 0 and x.parent.right is x:
-            self.__fix_0_child(
+            new_root = self.__fix_0_child(
-                x, x.left, x_parent, self.rotate_right, self.rotate_left
+                x, x.left, x_parent, Node.rotate_right, Node.rotate_left
             )
 
+        if rotating_around_root:
+            self.root = new_root
+
     # endregion InsertRebalance
 
     # region DeleteRebalance
@@ -96,6 +106,7 @@ class AVLTree(RankedTree[T]):
         x: Node[T],
         y: Node[T],
         leaning: int,
+        rotating_around_root: bool,
         rotate_left: RotateFunction[T],
         rotate_right: RotateFunction[T],
     ) -> bool:
@@ -111,10 +122,12 @@ class AVLTree(RankedTree[T]):
         for n in filter(None, (new_root.left, new_root.right, new_root)):
             _update_rank(n)
 
+        if rotating_around_root:
+            self.root = new_root
         return factor != 0
 
     def __delete_fixup(
-        self, x: Node[T], parent: Optional[Node[T]] = None
+        self, x: Optional[Node[T]], parent: Optional[Node[T]] = None
     ) -> bool:
         factor = _balance_factor(x)
         if factor == 0:
@@ -123,16 +136,18 @@ class AVLTree(RankedTree[T]):
         elif factor in (-1, 1):
             return False
 
+        rotating_around_root = x.parent is None
         y, leaning, to_left, to_right = (
-            (x.right, 1, self.rotate_left, self.rotate_right)
+            (x.right, 1, Node.rotate_left, Node.rotate_right)
             if factor == 2
-            else (x.left, -1, self.rotate_right, self.rotate_left)
+            else (x.left, -1, Node.rotate_right, Node.rotate_left)
         )
         assert y
         return self.__delete_rotate(
             x,
             y,
             leaning,
+            rotating_around_root,
             to_left,
             to_right,
         )
@@ -143,7 +158,7 @@ class AVLTree(RankedTree[T]):
         if not node and not parent:
             return
 
-        if not node and parent:
+        if not node:
             node, parent = parent, parent.parent
 
         while node and self.__delete_fixup(node, parent):

node.py

@@ -1,8 +1,8 @@
 from abc import abstractmethod
 import enum
 from typing import (
+    Callable,
     Iterable,
-    Iterator,
     Optional,
     Generic,
     Tuple,
@@ -28,7 +28,7 @@ class NodeType(enum.IntEnum):
 T = TypeVar("T", bound=Comparable)
 
 
-class Node(Generic[T], Iterable[T]):
+class Node(Generic[T]):
     def __init__(
         self,
         value: T,
@@ -62,7 +62,7 @@ class Node(Generic[T], Iterable[T]):
     def __str__(self) -> str:
         return f"Node(value={self.value}, rank={self.rank})"
 
-    def __iter__(self) -> Iterator[T]:
+    def __iter__(self) -> Iterable[T]:
         """
         Yields:
             Keys from the subtree rooted at the node in an inorder fashion.
@@ -111,10 +111,56 @@ class Node(Generic[T], Iterable[T]):
         self.rank -= 1
         return self
 
+    @staticmethod
+    def rotate_right(x: "Node[T]") -> "Node[T]":
+        parent = x.parent
+        y = x.left
+        # z = x.right
+
+        assert y is not None
+        if parent:
+            if parent.left is x:
+                parent.left = y
+            else:
+                parent.right = y
+
+        x.left = y.right
+        if x.left:
+            x.left.parent = x
+
+        y.right = x
+        x.parent = y
+        y.parent = parent
+
+        return y
+
+    @staticmethod
+    def rotate_left(x: "Node[T]") -> "Node[T]":
+        parent = x.parent
+        # y = x.left
+        z = x.right
+
+        assert z is not None
+        if parent:
+            if parent.left is x:
+                parent.left = z
+            else:
+                parent.right = z
+
+        x.right = z.left
+        if x.right:
+            x.right.parent = x
+
+        z.left = x
+        x.parent = z
+        z.parent = parent
+
+        return z
+
     @staticmethod
     def find_parent_node(
         value: T, node: "Node[T]", missing: bool = True
-    ) -> "Optional[Node[T]]":
+    ) -> "Node[T]":
         new_node: "Optional[Node[T]]" = node
 
         while new_node and (missing or new_node.value != value):
@@ -148,3 +194,6 @@ class Node(Generic[T], Iterable[T]):
             node = node.right
 
         return node
+
+
+RotateFunction = Callable[[Node[T]], Node[T]]

ranked_tree.py

@@ -3,7 +3,7 @@ from node import Node, Comparable
 from abc import abstractmethod
 from collections import deque
 import logging
-from typing import Callable, Deque, Iterable, Optional, Tuple, TypeVar, Generic
+from typing import Deque, Iterable, Optional, Tuple, TypeVar, Generic
 
 logger = logging.getLogger(__name__)
 T = TypeVar("T", bound=Comparable)
@@ -58,58 +58,6 @@ class RankedTree(Generic[T]):
 
     # endregion TreeSpecificMethods
 
-    # region Rotations
-
-    def rotate_right(self, x: "Node[T]") -> "Node[T]":
-        parent = x.parent
-        y = x.left
-        # z = x.right
-
-        assert y is not None
-        if parent:
-            if parent.left is x:
-                parent.left = y
-            else:
-                parent.right = y
-        else:
-            self.root = y
-
-        x.left = y.right
-        if x.left:
-            x.left.parent = x
-
-        y.right = x
-        x.parent = y
-        y.parent = parent
-
-        return y
-
-    def rotate_left(self, x: "Node[T]") -> "Node[T]":
-        parent = x.parent
-        # y = x.left
-        z = x.right
-
-        assert z is not None
-        if parent:
-            if parent.left is x:
-                parent.left = z
-            else:
-                parent.right = z
-        else:
-            self.root = z
-
-        x.right = z.left
-        if x.right:
-            x.right.parent = x
-
-        z.left = x
-        x.parent = z
-        z.parent = parent
-
-        return z
-
-    # endregion Rotations
-
     @property
     def rank(self) -> int:
         return Node.get_rank(self.root)
@@ -174,7 +122,8 @@ class RankedTree(Generic[T]):
             self._transplant(node, node.left)
         else:
             n = Node.minimum(node.right)
-            node.value, n.value = n.value, node.value
+            node.value = n.value
+            n.value = None
             return self._delete_node(n)
 
         return (y, parent)
@@ -199,6 +148,3 @@ class RankedTree(Generic[T]):
         """
         if self.root:
             yield from self.root
-
-
-RotateFunction = Callable[[Node[T]], Node[T]]

rbt.py

@@ -1,179 +0,0 @@
-from node import Node, Comparable
-from ranked_tree import RankedTree, RotateFunction
-
-import enum
-import logging
-from typing import Callable, Tuple, TypeVar, Optional
-
-logger = logging.getLogger(__name__)
-T = TypeVar("T", bound=Comparable)
-
-
-class Colour(enum.IntEnum):
-    """
-    Represents colour of the edge or node.
-    """
-
-    Red = 0
-    Black = 1
-
-
-def has_double_black(x: Optional[Node[T]]) -> bool:
-    """
-    Checks for double black child of x.
-
-    Args:
-        x: Node to be checked.
-
-    Returns:
-        `true`, if `x` has a double black node, `false` otherwise.
-    """
-    return x is not None and 2 in Node.differences(x)
-
-
-class RBTree(RankedTree[T]):
-    def is_correct_node(
-        self, node: Optional[Node[T]], recursive: bool = True
-    ) -> bool:
-        if not node:
-            return True
-
-        left, right = Node.differences(node)
-        if left not in (Colour.Red, Colour.Black):
-            # left subtree has invalid difference
-            return False
-        elif right not in (Colour.Red, Colour.Black):
-            # right subtree has invalid difference
-            return False
-
-        if Node.difference(node) == Colour.Red and (
-            left == Colour.Red or right == Colour.Red
-        ):
-            # two consecutive red nodes
-            return False
-
-        return not recursive or (
-            self.is_correct_node(node.left)
-            and self.is_correct_node(node.right)
-        )
-
-    # region InsertRebalance
-
-    def _insert_rebalance_step(
-        self,
-        z: Node[T],
-        y: Optional[Node[T]],
-        right_child: Node[T],
-        rotate_left: RotateFunction[T],
-        rotate_right: RotateFunction[T],
-    ) -> Node[T]:
-        p = z.parent
-        pp = p.parent
-
-        if y is not None and Node.difference(y) == Colour.Red:
-            # Case 1
-            # ======
-            # z’s uncle y is red
-            pp.rank += Colour.Black
-            z = pp
-        elif z == right_child:
-            # Case 2
-            # ======
-            # z’s uncle y is black and z is a right child
-            z = p
-            rotate_left(p)
-        else:
-            # Case 3
-            # ======
-            # z’s uncle y is black and z is a left child
-            rotate_right(pp)
-
-        return z
-
-    def _insert_rebalance(self, z: Node[T]) -> None:
-        while z.parent is not None and Node.difference(z.parent) == Colour.Red:
-            p = z.parent
-            pp = p.parent
-
-            assert pp
-            if p == pp.left:
-                z = self._insert_rebalance_step(
-                    z, pp.right, p.right, self.rotate_left, self.rotate_right
-                )
-            else:
-                z = self._insert_rebalance_step(
-                    z, pp.left, p.left, self.rotate_right, self.rotate_left
-                )
-
-    # endregion InsertRebalance
-
-    # region DeleteRebalance
-
-    def _delete_rebalance_step(
-        self,
-        x: Node[T],
-        w: Node[T],
-        parent: Node[T],
-        right: Callable[[Node[T]], Optional[Node[T]]],
-        rotate_left: RotateFunction[T],
-        rotate_right: RotateFunction[T],
-    ) -> Tuple[Optional[Node[T]], Optional[Node[T]]]:
-        if Node.difference(w) == Colour.Red:
-            # Case 1
-            # ======
-            # x’s sibling w is red
-            rotate_left(parent)
-            w = right(parent)
-
-        if Node.differences(w) == (Colour.Black, Colour.Black):
-            # Case 2
-            # ======
-            # x’s sibling w is black, and both of w’s children are black
-            parent.rank -= Colour.Black
-            x = parent
-        else:
-            # Case 3
-            # ======
-            # x’s sibling w is black,
-            # w’s left child is red, and w’s right child is black
-            if Node.difference(right(w), w) == Colour.Black:
-                rotate_right(w)
-                w = right(parent)
-
-            # Case 4
-            # ======
-            # x’s sibling w is black, and w’s right child is red
-            parent.rank -= Colour.Black
-            w.rank += Colour.Black
-            rotate_left(parent)
-            x = self.root
-
-        return x, (x.parent if x else None)
-
-    def _delete_rebalance(
-        self, node: Optional[Node[T]], parent: Optional[Node[T]]
-    ) -> None:
-        if not node and not parent:
-            return
-
-        while node != self.root and has_double_black(parent):
-            if node == parent.left:
-                node, parent = self._delete_rebalance_step(
-                    node,
-                    parent.right,
-                    parent,
-                    lambda x: x.right,
-                    self.rotate_left,
-                    self.rotate_right,
-                )
-            else:
-                node, parent = self._delete_rebalance_step(
-                    node,
-                    parent.left,
-                    parent,
-                    lambda x: x.left,
-                    self.rotate_right,
-                    self.rotate_left,
-                )
-
-    # endregion DeleteRebalance

test_avl.py

@@ -1,8 +1,11 @@
 from avl import AVLTree, _balance_factor
 
 import logging
+import random
 from typing import List
 
+import hypothesis
+import hypothesis.strategies as st
 import pytest
 
 logger = logging.getLogger(__name__)

test_properties.py

@@ -1,10 +1,10 @@
 from avl import AVLTree
 from wavl import WAVLTree
 from ravl import RAVLTree
-from rbt import RBTree
 
 import logging
 import random
+from typing import List
 
 import hypothesis
 import hypothesis.strategies as st
@@ -14,7 +14,8 @@ logger = logging.getLogger(__name__)
 
 
 @pytest.mark.parametrize(
-    ("RankBalancedTree"), [RBTree, AVLTree, WAVLTree, RAVLTree]
+    ("RankBalancedTree"),
+    [AVLTree, WAVLTree, RAVLTree]
 )
 @hypothesis.settings(max_examples=10000)
 @hypothesis.given(values=st.sets(st.integers()))
@@ -44,7 +45,8 @@ def _report(t_before: str, t_after: str) -> None:
 
 
 @pytest.mark.parametrize(
-    ("RankBalancedTree"), [RBTree, AVLTree, WAVLTree, RAVLTree]
+    ("RankBalancedTree"),
+    [AVLTree, WAVLTree, RAVLTree]
 )
 @hypothesis.settings(max_examples=10000)
 @hypothesis.given(config=delete_strategy())

test_ravl.py

@@ -1,7 +1,10 @@
 from ravl import RAVLTree
 
+import hypothesis
+import hypothesis.strategies as st
 import logging
 import pytest
+import random
 
 logger = logging.getLogger(__name__)
 

test_rbt.py

@@ -1,43 +0,0 @@
-from rbt import RBTree
-
-import logging
-import pytest
-
-logger = logging.getLogger(__name__)
-
-
-@pytest.mark.parametrize(
-    "values, delete_order",
-    [
-        ([0, 1, -1], [0, -1, 1]),
-        ([0, 1, 2, 3, 4, 5], [4, 2, 1, 0, 5, 3]),
-        (
-            [32, 1, 2, 3, 4, 5, 0, -2, -4, -3, -1],
-            [-4, -3, 1, 2, 5, 3, -2, 4, 32, -1, 0],
-        ),
-        ([0, 1, 2, -2, -3, -1], [-3, 2, 1, 0, -1, -2]),
-        ([0, 1, 2, 3, 4, 5, -1], [4, 2, 1, 0, 5, 3, -1]),
-    ],
-)
-def test_delete_minimal(values, delete_order):
-    tree = RBTree()
-
-    for value in values:
-        tree.insert(value)
-
-    for value in delete_order:
-        logger.info("Deleting %s", value)
-
-        before = str(tree)
-        tree.delete(value)
-        after = str(tree)
-
-        try:
-            assert tree.is_correct
-        except AssertionError:
-            logger.info(
-                f"[FAIL] Delete {value} from {values} in order {delete_order}"
-            )
-            logger.info(f"Before:\n{before}")
-            logger.info(f"After:\n{after}")
-            raise

wavl.py

@@ -1,6 +1,5 @@
-from ranked_tree import RotateFunction
 from avl import AVLTree
-from node import Node, NodeType, Comparable
+from node import Node, NodeType, Comparable, RotateFunction
 
 import logging
 from typing import TypeVar, Optional
@@ -36,9 +35,11 @@ class WAVLTree(AVLTree[T]):
         y: Node[T],
         z: Node[T],
         reversed: bool,
+        rotating_around_root: bool,
         rotate_left: RotateFunction[T],
         rotate_right: RotateFunction[T],
     ) -> None:
+        new_root = x
         v = y.left
         w = y.right
 
@@ -48,7 +49,9 @@ class WAVLTree(AVLTree[T]):
         w_diff = Node.difference(w, y)
 
         if w_diff == 1 and y.parent:
-            rotate_left(y.parent)
+            new_root = rotate_left(y.parent)
+            if rotating_around_root:
+                self.root = new_root
 
             y.promote()
             z.demote()
@@ -57,7 +60,9 @@ class WAVLTree(AVLTree[T]):
                 z.demote()
         elif w_diff == 2 and v.parent:
             rotate_right(v.parent)
-            rotate_left(v.parent)
+            new_root = rotate_left(v.parent)
+            if rotating_around_root:
+                self.root = new_root
 
             v.promote().promote()
             y.demote()
@@ -92,6 +97,8 @@ class WAVLTree(AVLTree[T]):
             x_diff = Node.difference(x, parent)
             y_diff = Node.difference(y, parent)
 
+        rotating_around_root = parent.parent is None
+
         parent_node_diffs = Node.differences(parent)
         if parent_node_diffs in ((1, 3), (3, 1)):
             if parent.left is x:
@@ -101,8 +108,9 @@ class WAVLTree(AVLTree[T]):
                     parent.right,
                     parent,
                     False,
-                    self.rotate_left,
+                    rotating_around_root,
-                    self.rotate_right,
+                    Node.rotate_left,
+                    Node.rotate_right,
                 )
             else:
                 assert parent.left
@@ -111,8 +119,9 @@ class WAVLTree(AVLTree[T]):
                     parent.left,
                     parent,
                     True,
-                    self.rotate_right,
+                    rotating_around_root,
-                    self.rotate_left,
+                    Node.rotate_right,
+                    Node.rotate_left,
                 )
 
     def _delete_rebalance(