Add miscellaneous python code that I want to keep.
This commit is contained in:
231
resources/python/btree.py
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231
resources/python/btree.py
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import bisect
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class BTreePrinter(object):
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number_width = 4
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subtree_space = object()
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def __init__(self, btree):
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self.btree = btree
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def determine_width_of_node(self, node):
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if node is None: return 0
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return sum(map(self.determine_width_of_node, node.nodes)) + node.number_of_value_nodes * self.number_width
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def determine_width_of_value_node(self, value_node):
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return self.determine_width_of_node(value_node.node) if value_node.node is not None else self.number_width
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def print_tree(self):
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return self.print_levels_recursively([self.btree.head])
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def print_levels_recursively(self, level):
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if all(map(lambda x: x is self.subtree_space, level)): return
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self.print_nodes_at_level(level)
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print ''
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self.print_levels_recursively(self.get_next_level(level))
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def get_next_level(self, level):
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new_level = []
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for item in level:
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if item is self.subtree_space:
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new_level.append(item)
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elif item is not None:
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new_level.extend(item.nodes)
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new_level.append(self.subtree_space)
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return new_level
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def print_nodes_at_level(self, level):
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for item in level:
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if item is self.subtree_space:
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print ' ' * self.number_width,
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else:
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self.print_values_for_node(item)
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def print_values_for_node(self, node):
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if node is None: return
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for value_node in node.value_nodes:
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print ' ' * self.determine_width_of_node(value_node.node),
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print '{num: ^{width}}'.format(num=value_node.value, width=self.number_width),
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print (' ' * (self.determine_width_of_node(node.rightmost_node))),
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class IntegrityChecker(object):
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def __init__(self, btree):
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self.btree = btree
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def check_integrity(self):
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return self.check_for_items_smaller_in_right_subtree(self.btree.head) and self.check_for_unmatched_parents(self.btree.head)
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def check_for_unmatched_parents(self, subtree):
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if subtree is None:
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return True
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for node in subtree.nodes:
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if node is None:
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continue
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if node.parent is not subtree:
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return False
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if not self.check_for_unmatched_parents(node):
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return False
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return True
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def check_for_items_smaller_in_right_subtree(self, subtree):
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if subtree is None:
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return True
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small_value = subtree.value_nodes[0].value
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for value_node in subtree.value_nodes[1:]:
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if not self.check_subtree_has_no_items_smaller_than(value_node.node, small_value):
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return False
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if not self.check_for_items_smaller_in_right_subtree(subtree.value_nodes[0].node):
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return False
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return self.check_subtree_has_no_items_smaller_than(subtree.rightmost_node, small_value)
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def check_subtree_has_no_items_smaller_than(self, subtree, value):
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if subtree is None:
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return True
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for value_node in subtree.value_nodes:
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if value > value_node.value:
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return False
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if not self.check_subtree_has_no_items_smaller_than(value_node.node, value):
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return False
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return self.check_subtree_has_no_items_smaller_than(subtree.rightmost_node, value)
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class BTree(object):
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@classmethod
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def build_with_value(cls, value):
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btree = cls()
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btree.head = Node(btree, [ValueNode(value)])
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return btree
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def __init__(self):
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self.head = None
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self.inserted_items = []
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def build_new_head(self, value_node):
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new_rightmost_node = self.head
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self.head = Node(self, [value_node])
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value_node.node.parent = self.head
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self.head.rightmost_node = new_rightmost_node
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new_rightmost_node.parent = self.head
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assert self.head.rightmost_node is not None
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return value_node
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def insert(self, value):
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self.head.insert(value)
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self.inserted_items.append(value)
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self.head.check_integrity()
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if not IntegrityChecker(self).check_integrity():
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import ipdb; ipdb.set_trace()
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promote_value_node = build_new_head
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def __repr__(self):
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return "BTree({0})".format(repr(self.head))
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class ValueNode(object):
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def __init__(self, value, node=None):
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self.value = value
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self.node = node
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def __lt__(self, other):
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return self.value < other.value
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def __gt__(self, other):
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return self.value > other.value
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def __repr__(self):
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return "ValueNode({0}, {1})".format(repr(self.node), repr(self.value))
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class Node(object):
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max_num_values = 3
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def __init__(self, parent, value_nodes=None, rightmost_node=None):
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self.parent = parent
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self.value_nodes = value_nodes or []
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self.rightmost_node = rightmost_node
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self.claim_child_nodes()
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def check_integrity(self):
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if self.is_leaf_node: return True
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if self.rightmost_node:
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return all(child_node.check_integrity() for child_node in self.nodes if child_node is not None)
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import ipdb; ipdb.set_trace()
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return False
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def claim_child_nodes(self):
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for node in self.nodes:
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if node:
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node.parent = self
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@property
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def is_leaf_node(self):
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return not any(self.nodes)
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@property
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def number_of_value_nodes(self):
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return len(self.value_nodes)
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@property
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def nodes(self):
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return [value_node.node for value_node in self.value_nodes] + [self.rightmost_node]
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@property
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def values(self):
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return [value_node.value for value_node in self.value_nodes]
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def __getitem__(self, item):
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return self.nodes[item]
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def promote_value_node(self, value_node):
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bisect.insort(self.value_nodes, value_node)
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if value_node.node:
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value_node.node.parent = self
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self.maybe_rebalance()
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def maybe_rebalance(self):
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if self.number_of_value_nodes < self.max_num_values:
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return
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value_node_to_promote = self.value_nodes[self.number_of_value_nodes/2]
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promoted_nodes_old_node = value_node_to_promote.node
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value_node_to_promote.node = Node(
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self.parent,
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value_nodes=self.value_nodes[:self.number_of_value_nodes/2],
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rightmost_node=promoted_nodes_old_node
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)
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self.value_nodes = self.value_nodes[self.number_of_value_nodes/2+1:]
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self.parent.promote_value_node(value_node_to_promote)
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self.check_integrity()
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def insert(self, value):
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if self.is_leaf_node:
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value_node = ValueNode(value)
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bisect.insort(self.value_nodes, value_node)
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self.maybe_rebalance()
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return value_node
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return self.pick_node(value).insert(value)
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def pick_node(self, value):
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if self.rightmost_node is None:
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import ipdb; ipdb.set_trace()
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for value_node in self.value_nodes:
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if value < value_node.value:
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return value_node.node
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return self.rightmost_node
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def __repr__(self):
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return "Node({0}, {1})".format(", ".join(map(repr, self.value_nodes)), self.rightmost_node)
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