ci: add GitLab CI

Signed-off-by: Matej Focko <mfocko@redhat.com>

.gitlab-ci.yml

@@ -0,0 +1,42 @@
+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
+	pytest -vvv --log-level debug --cov --cov-report=term-missing --cov-report=xml:coverage.xml --junitxml=report.xml
 
 lint: black flake8 mypy
 
@@ -10,7 +10,7 @@ flake8:
 	flake8 *.py
 
 mypy:
-	mypy --strict --disallow-any-explicit node.py avl.py wavl.py ravl.py
+	mypy --strict --disallow-any-explicit node.py ranked_tree.py avl.py wavl.py ravl.py rbt.py
 
 clean:
 	rm -rf __pycache__ .hypothesis .mypy_cache .pytest_cache

avl.py

@@ -1,5 +1,5 @@
-from node import Node, Comparable, RotateFunction
-from ranked_tree import RankedTree
+from node import Node, Comparable
+from ranked_tree import RankedTree, RotateFunction
 
 import logging
 from typing import TypeVar, Optional
@@ -49,22 +49,18 @@ class AVLTree(RankedTree[T]):
         z: Node[T],
         rotate_left: RotateFunction[T],
         rotate_right: RotateFunction[T],
-    ) -> Optional[Node[T]]:
-        new_root = x.parent
-
+    ) -> None:
         if not y or Node.difference(y) == 2:
-            new_root = rotate_right(z)
+            rotate_right(z)
             z.demote()
         elif Node.difference(y) == 1:
             rotate_left(x)
-            new_root = rotate_right(z)
+            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)):
@@ -76,9 +72,6 @@ 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
@@ -86,17 +79,14 @@ class AVLTree(RankedTree[T]):
         x_parent = x.parent
         assert x_parent is not None
         if rank_difference == 0 and x.parent.left is x:
-            new_root = self.__fix_0_child(
-                x, x.right, x_parent, Node.rotate_left, Node.rotate_right
+            self.__fix_0_child(
+                x, x.right, x_parent, self.rotate_left, self.rotate_right
             )
         elif rank_difference == 0 and x.parent.right is x:
-            new_root = self.__fix_0_child(
-                x, x.left, x_parent, Node.rotate_right, Node.rotate_left
+            self.__fix_0_child(
+                x, x.left, x_parent, self.rotate_right, self.rotate_left
             )
 
-        if rotating_around_root:
-            self.root = new_root
-
     # endregion InsertRebalance
 
     # region DeleteRebalance
@@ -106,7 +96,6 @@ 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:
@@ -122,12 +111,10 @@ 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: Optional[Node[T]], parent: Optional[Node[T]] = None
+        self, x: Node[T], parent: Optional[Node[T]] = None
     ) -> bool:
         factor = _balance_factor(x)
         if factor == 0:
@@ -136,18 +123,16 @@ 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, Node.rotate_left, Node.rotate_right)
+            (x.right, 1, self.rotate_left, self.rotate_right)
             if factor == 2
-            else (x.left, -1, Node.rotate_right, Node.rotate_left)
+            else (x.left, -1, self.rotate_right, self.rotate_left)
         )
         assert y
         return self.__delete_rotate(
             x,
             y,
             leaning,
-            rotating_around_root,
             to_left,
             to_right,
         )
@@ -158,7 +143,7 @@ class AVLTree(RankedTree[T]):
         if not node and not parent:
             return
 
-        if not node:
+        if not node and parent:
             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]):
+class Node(Generic[T], Iterable[T]):
     def __init__(
         self,
         value: T,
@@ -62,7 +62,7 @@ class Node(Generic[T]):
     def __str__(self) -> str:
         return f"Node(value={self.value}, rank={self.rank})"
 
-    def __iter__(self) -> Iterable[T]:
+    def __iter__(self) -> Iterator[T]:
         """
         Yields:
             Keys from the subtree rooted at the node in an inorder fashion.
@@ -111,56 +111,10 @@ class Node(Generic[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
-    ) -> "Node[T]":
+    ) -> "Optional[Node[T]]":
         new_node: "Optional[Node[T]]" = node
 
         while new_node and (missing or new_node.value != value):
@@ -194,6 +148,3 @@ class Node(Generic[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 Deque, Iterable, Optional, Tuple, TypeVar, Generic
+from typing import Callable, Deque, Iterable, Optional, Tuple, TypeVar, Generic
 
 logger = logging.getLogger(__name__)
 T = TypeVar("T", bound=Comparable)
@@ -58,6 +58,58 @@ 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)
@@ -122,8 +174,7 @@ class RankedTree(Generic[T]):
             self._transplant(node, node.left)
         else:
             n = Node.minimum(node.right)
-            node.value = n.value
-            n.value = None
+            node.value, n.value = n.value, node.value
             return self._delete_node(n)
 
         return (y, parent)
@@ -148,3 +199,6 @@ class RankedTree(Generic[T]):
         """
         if self.root:
             yield from self.root
+
+
+RotateFunction = Callable[[Node[T]], Node[T]]

rbt.py

@@ -0,0 +1,179 @@
+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

@@ -1,11 +1,8 @@
 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
@@ -14,8 +14,7 @@ logger = logging.getLogger(__name__)
 
 
 @pytest.mark.parametrize(
-    ("RankBalancedTree"),
-    [AVLTree, WAVLTree, RAVLTree]
+    ("RankBalancedTree"), [RBTree, AVLTree, WAVLTree, RAVLTree]
 )
 @hypothesis.settings(max_examples=10000)
 @hypothesis.given(values=st.sets(st.integers()))
@@ -45,8 +44,7 @@ def _report(t_before: str, t_after: str) -> None:
 
 
 @pytest.mark.parametrize(
-    ("RankBalancedTree"),
-    [AVLTree, WAVLTree, RAVLTree]
+    ("RankBalancedTree"), [RBTree, AVLTree, WAVLTree, RAVLTree]
 )
 @hypothesis.settings(max_examples=10000)
 @hypothesis.given(config=delete_strategy())

test_ravl.py

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

test_rbt.py

@@ -0,0 +1,43 @@
+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

@@ -1,5 +1,6 @@
+from ranked_tree import RotateFunction
 from avl import AVLTree
-from node import Node, NodeType, Comparable, RotateFunction
+from node import Node, NodeType, Comparable
 
 import logging
 from typing import TypeVar, Optional
@@ -35,11 +36,9 @@ 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
 
@@ -49,9 +48,7 @@ class WAVLTree(AVLTree[T]):
         w_diff = Node.difference(w, y)
 
         if w_diff == 1 and y.parent:
-            new_root = rotate_left(y.parent)
-            if rotating_around_root:
-                self.root = new_root
+            rotate_left(y.parent)
 
             y.promote()
             z.demote()
@@ -60,9 +57,7 @@ class WAVLTree(AVLTree[T]):
                 z.demote()
         elif w_diff == 2 and v.parent:
             rotate_right(v.parent)
-            new_root = rotate_left(v.parent)
-            if rotating_around_root:
-                self.root = new_root
+            rotate_left(v.parent)
 
             v.promote().promote()
             y.demote()
@@ -97,8 +92,6 @@ 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:
@@ -108,9 +101,8 @@ class WAVLTree(AVLTree[T]):
                     parent.right,
                     parent,
                     False,
-                    rotating_around_root,
-                    Node.rotate_left,
-                    Node.rotate_right,
+                    self.rotate_left,
+                    self.rotate_right,
                 )
             else:
                 assert parent.left
@@ -119,9 +111,8 @@ class WAVLTree(AVLTree[T]):
                     parent.left,
                     parent,
                     True,
-                    rotating_around_root,
-                    Node.rotate_right,
-                    Node.rotate_left,
+                    self.rotate_right,
+                    self.rotate_left,
                 )
 
     def _delete_rebalance(