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CATEGORIES = { | ||
color: %i[ | ||
red | ||
green | ||
blue | ||
yellow | ||
ivory | ||
].freeze, | ||
nationality: %i[ | ||
englishman | ||
spaniard | ||
ukrainian | ||
norwegian | ||
japanese | ||
].freeze, | ||
beverage: %i[ | ||
coffee | ||
tea | ||
milk | ||
orange_juice | ||
water | ||
].freeze, | ||
cigarette: %i[ | ||
old_gold | ||
kool | ||
chesterfield | ||
lucky_strike | ||
parliament | ||
].freeze, | ||
pet: %i[ | ||
dog | ||
snails | ||
fox | ||
horse | ||
zebra | ||
].freeze | ||
}.freeze | ||
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House = Data.define(*CATEGORIES.keys) | ||
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module ZebraPuzzle | ||
def self.water_drinker | ||
houses.find { _1.beverage == :water }.nationality.to_s.capitalize | ||
end | ||
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def self.zebra_owner | ||
houses.find { _1.pet == :zebra }.nationality.to_s.capitalize | ||
end | ||
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private_class_method def self.houses | ||
@houses ||= ZebraPuzzleSolver.new.final_row_of_houses | ||
end | ||
end | ||
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class ZebraPuzzleSolver | ||
def initialize | ||
@table = null_table | ||
end | ||
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def final_row_of_houses | ||
return @table unless @table == null_table | ||
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CATEGORIES.each_key do |key| | ||
add_into_table!(key) | ||
send("filter_by_#{key}!") | ||
end | ||
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raise "More than one final possibility exists" if @table.count > 1 | ||
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@table.first | ||
end | ||
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private | ||
def null_table | ||
null_house = CATEGORIES.keys.to_h { |key| [key, nil] } | ||
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# Clue: There are five houses. | ||
[[null_house] * 5] | ||
end | ||
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def add_into_table!(new_key) | ||
permutations = CATEGORIES.fetch(new_key).permutation | ||
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@table.map! do |houses| | ||
permutations.map do |new_values| | ||
houses.zip(new_values).map do |house, new_value| | ||
House.new(**house.to_h.merge(new_key => new_value)) | ||
end | ||
end | ||
end.flatten!(1) | ||
end | ||
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def filter_by_color! | ||
@table.select! do |houses| | ||
# Clue: The green house is immediately to the right of the ivory house. | ||
houses.index { _1.color == :green } == houses.index { _1.color == :ivory } + 1 && | ||
# (Clue: The second house is blue. From these clues:) | ||
# - The Norwegian lives in the first house. | ||
# - The Norwegian lives next to the blue house. | ||
houses.index { _1.color == :blue } == 1 | ||
end | ||
end | ||
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def filter_by_nationality! | ||
@table.select! do |houses| | ||
# Clue: The Englishman lives in the red house. | ||
houses.any? { _1.nationality == :englishman && _1.color == :red } && | ||
# Clue: The Norwegian lives in the first house. | ||
houses.first.nationality == :norwegian | ||
end | ||
end | ||
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def filter_by_beverage! | ||
@table.select! do |houses| | ||
# Clue: Coffee is drunk in the green house. | ||
houses.any? { _1.beverage == :coffee && _1.color == :green } && | ||
# Clue: The Ukrainian drinks tea. | ||
houses.any? { _1.nationality == :ukrainian && _1.beverage == :tea } && | ||
# Clue: Milk is drunk in the middle house. | ||
houses[2].beverage == :milk | ||
end | ||
end | ||
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def filter_by_cigarette! | ||
@table.select! do |houses| | ||
# Clue: Kools are smoked in the yellow house. | ||
houses.any? { _1.cigarette == :kool && _1.color == :yellow } && | ||
# Clue: The Lucky Strike smoker drinks orange juice. | ||
houses.any? { _1.cigarette == :lucky_strike && _1.beverage == :orange_juice } && | ||
# Clue: The Japanese smokes Parliaments. | ||
houses.any? { _1.nationality == :japanese && _1.cigarette == :parliament } | ||
end | ||
end | ||
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# rubocop:disable Metrics/AbcSize | ||
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def filter_by_pet! | ||
@table.select! do |houses| | ||
# Clue: The Spaniard owns the dog. | ||
houses.any? { _1.nationality == :spaniard && _1.pet == :dog } && | ||
# Clue: The Old Gold smoker owns snails. | ||
houses.any? { _1.cigarette == :old_gold && _1.pet == :snails } && | ||
# Clue: The man who smokes Chesterfields lives in the house next to the man with the fox. | ||
(houses.index { _1.cigarette == :chesterfield } - houses.index { _1.pet == :fox }).abs == 1 && | ||
# Clue: Kools are smoked in the house next to the house where the horse is kept. | ||
(houses.index { _1.cigarette == :kool } - houses.index { _1.pet == :horse }).abs == 1 | ||
end | ||
end | ||
# rubocop:enable Metrics/AbcSize | ||
end |