programming-examples/ruby/Data_Structures/m_way_tree.rb

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2019-11-15 12:59:38 +01:00
# This file contains the Ruby code from book of
# "Data Structures and Algorithms
# with Object-Oriented Design Patterns in Ruby"
# by Bruno R. Preiss.
#
# Copyright (c) 2004 by Bruno R. Preiss, P.Eng. All rights reserved.
class MWayTree < SearchTree
def initialize(m)
assert { m > 2 }
super()
@key = Array.new(m - 1, 1)
@subtree = Array.new(m)
end
def m
@subtree.length
end
def depthFirstTraversal(&block)
if not empty?
for i in 1 .. @count
yield (@key[i], PREVISIT)
end
@subtree[0].depthFirstTraversal(&block)
for i in 1 .. @count
yield (@key[i], INVISIT)
@subtree[i].depthFirstTraversal(&block)
end
for i in 1 .. @count
yield (@key[i], POSTVISIT)
end
end
end
def find(obj)
return nil if empty?
i = @count
while i > 0
diff = obj <=> @key[i]
return @key[i] if diff == 0
break if diff > 0
i = i - 1
end
return @subtree[i].find(obj)
end
def findIndex(obj)
return 0 if empty? or obj < @key[1]
left = 1
right = @count
while left < right
middle = (left + right + 1) / 2
if obj < @key[middle]
right = middle - 1
else
left = middle
end
end
return left
end
def find(obj)
return nil if empty?
index = findIndex(obj)
if index != 0 and @key[index] == obj
return @key[index]
else
return @subtree[index].find(obj)
end
end
def insert(obj)
if empty?
@subtree[0] = MWayTree.new(m)
@key[1] = obj
@subtree[1] = MWayTree.new(m)
@count = 1
else
index = findIndex(obj)
raise ValueError if index != 0 and @key[index] == obj
if not full?
i = @count
while i > index
@key[i + 1] = @key[i]
@subtree[i + 1] = @subtree[i]
i = i - 1
end
@key[index + 1] = obj
@subtree[index + 1] = MWayTree.new(m)
@count = @count + 1
else
@subtree[index].insert(obj)
end
end
end
def withdraw(obj)
raise ArgumentError if empty?
index = findIndex(obj)
if index != 0 and @key[index] == obj
if not @subtree[index - 1].empty?
max = @subtree[index - 1].max
@key[index] = max
@subtree[index - 1].withdraw(max)
elsif not @subtree[index].empty?
min = @subtree[index].min
@key[index] = min
@subtree[index].withdraw(min)
else
@count = @count - 1
i = index
while i <= @count
@key[i] = @key[i + 1]
@subtree[i] = @subtree[i + 1]
i = i + 1
end
@key[i] = nil
@subtree[i] = nil
if @count == 0
@subtree[0] = nil
end
end
else
@subtree[index].withdraw(obj)
end
end
end