From: Scott Gasch Date: Fri, 5 May 2023 02:37:44 +0000 (-0700) Subject: Better definition of "fuzzy". X-Git-Url: https://wannabe.guru.org/gitweb/?a=commitdiff_plain;h=7de2deb0d10689aca02918fb99b9baa0bc2cb7ac;p=pyutils.git Better definition of "fuzzy". --- diff --git a/src/pyutils/collectionz/bst.py b/src/pyutils/collectionz/bst.py index a4316a5..5fd36e0 100644 --- a/src/pyutils/collectionz/bst.py +++ b/src/pyutils/collectionz/bst.py @@ -113,18 +113,64 @@ class BinarySearchTree(object): return self._find(value, node.right) return None - def _find_fuzzy(self, value: Any, node: Node) -> Node: - """Find helper that returns the closest node <= the target value.""" - if value == node.value: - return node - below = None - if value < node.value and node.left is not None: - below = self._find_fuzzy(value, node.left) - elif value > node.value and node.right is not None: - below = self._find_fuzzy(value, node.right) - if not below: + def _find_lowest_value_greater_than_or_equal_to( + self, target: Any, node: Optional[Node] + ) -> Optional[Node]: + """Find helper that returns the lowest node that is greater + than or equal to the target value. Returns None if target is + greater than the highest node in the tree. + + >>> t = BinarySearchTree() + >>> t.insert(50) + >>> t.insert(75) + >>> t.insert(25) + >>> t.insert(66) + >>> t.insert(22) + >>> t.insert(13) + >>> t.insert(85) + >>> t + 50 + ├──25 + │ └──22 + │ └──13 + └──75 + ├──66 + └──85 + + >>> t._find_lowest_value_greater_than_or_equal_to(48, t.root).value + 50 + >>> t._find_lowest_value_greater_than_or_equal_to(55, t.root).value + 66 + >>> t._find_lowest_value_greater_than_or_equal_to(1, t.root).value + 13 + >>> t._find_lowest_value_greater_than_or_equal_to(24, t.root).value + 25 + >>> t._find_lowest_value_greater_than_or_equal_to(20, t.root).value + 22 + >>> t._find_lowest_value_greater_than_or_equal_to(72, t.root).value + 75 + >>> t._find_lowest_value_greater_than_or_equal_to(78, t.root).value + 85 + >>> t._find_lowest_value_greater_than_or_equal_to(95, t.root) is None + True + + """ + + if not node: + return None + + if target == node.value: return node - return below + elif target >= node.value: + return self._find_lowest_value_greater_than_or_equal_to(target, node.right) + else: + assert target < node.value + if below := self._find_lowest_value_greater_than_or_equal_to( + target, node.left + ): + return below + else: + return node def _parent_path( self, current: Optional[Node], target: Node @@ -642,7 +688,9 @@ class BinarySearchTree(object): 50 66 """ - node: Optional[Node] = self._find_fuzzy(lower, self.root) + node: Optional[Node] = self._find_lowest_value_greater_than_or_equal_to( + lower, self.root + ) while node: if lower <= node.value <= upper: yield node