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rb-tree #5

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mfocko merged 3 commits from rb-tree into main 2022-05-20 15:48:38 +02:00
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1 changed files with 7 additions and 7 deletions
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rbt.py
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@ -61,7 +61,7 @@ class RBTree(RankedTree[T]):
# Case 1 # Case 1
# ====== # ======
# z’s uncle y is red # z’s uncle y is red
pp.rank += 1 pp.rank += Colour.Black
z = pp z = pp
elif z == right_child: elif z == right_child:
# Case 2 # Case 2
@ -105,33 +105,33 @@ class RBTree(RankedTree[T]):
rotate_left: RotateFunction, rotate_left: RotateFunction,
rotate_right: RotateFunction, rotate_right: RotateFunction,
) -> Tuple[Optional[Node[T]], Optional[Node[T]]]: ) -> Tuple[Optional[Node[T]], Optional[Node[T]]]:
if Node.difference(w) == 0: if Node.difference(w) == Colour.Red:
# Case 1 # Case 1
# ====== # ======
# x’s sibling w is red # x’s sibling w is red
rotate_left(tree=self, x=parent) rotate_left(tree=self, x=parent)
w = right(parent) w = right(parent)
if Node.differences(w) == (1, 1): if Node.differences(w) == (Colour.Black, Colour.Black):
# Case 2 # Case 2
# ====== # ======
# x’s sibling w is black, and both of w’s children are black # x’s sibling w is black, and both of w’s children are black
parent.rank -= 1 parent.rank -= Colour.Black
x = parent x = parent
else: else:
# Case 3 # Case 3
# ====== # ======
# x’s sibling w is black, # x’s sibling w is black,
# w’s left child is red, and w’s right child is black # w’s left child is red, and w’s right child is black
if Node.difference(right(w), w) == 1: if Node.difference(right(w), w) == Colour.Black:
rotate_right(tree=self, x=w) rotate_right(tree=self, x=w)
w = right(parent) w = right(parent)
# Case 4 # Case 4
# ====== # ======
# x’s sibling w is black, and w’s right child is red # x’s sibling w is black, and w’s right child is red
parent.rank -= 1 parent.rank -= Colour.Black
w.rank += 1 w.rank += Colour.Black
rotate_left(tree=self, x=parent) rotate_left(tree=self, x=parent)
x = self.root x = self.root