32 lines
964 B
Crystal
32 lines
964 B
Crystal
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require "advent"
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input = input(2020, 21).lines.map do |line|
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data = line.match(/^([a-z ]+) \(contains (.+)\)$/).not_nil!
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{data[1].split(" ").to_set, data[2].split(", ").to_set}
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end
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allergens = input.flat_map(&.last.to_a).to_set
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ingredients = input.flat_map(&.first.to_a).to_set
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allergen_sets = {} of String => Set(String)
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allergens.each do |a|
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input.each do |ings, als|
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next unless als.includes? a
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allergen_sets[a] ||= ings
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allergen_sets[a] &= ings
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end
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end
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safe = ingredients.reject { |i| allergen_sets.any? &.last.includes?(i) }
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puts "Part 1: #{input.sum &.first.count { |i| safe.includes? i }}"
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known_allergens = {} of String => String
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while allergen_sets.size > known_allergens.size
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allergen_sets.each do |a, s|
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next unless s.size == 1
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new_known = s.first
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known_allergens[a] = new_known
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allergen_sets.each &.last.delete(new_known)
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end
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end
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puts "Part 2: #{known_allergens.to_a.sort_by(&.first).map(&.last).join(",")}"
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