90 lines
1.6 KiB
Ruby
90 lines
1.6 KiB
Ruby
# frozen_string_literal: true
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require 'set'
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class Body
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attr_reader :name, :satellites
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attr_accessor :parent
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def initialize(name)
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@name = name
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@satellites = []
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end
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def <<(satellite)
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@satellites << satellite
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satellite.parent = self
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end
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def inspect
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"<Body #{name}, #{satellites.map(&:name).inspect}>"
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end
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def to_s
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name
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end
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def direct_orbits
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@direct_orbits ||= @satellites.length + @satellites.sum(&:direct_orbits)
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end
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def indirect_orbits(depth = 0)
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@indirect_orbits ||= @satellites.sum do |sat|
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depth + sat.indirect_orbits(depth + 1)
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end
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end
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@@registry = {}
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def self.get_or_create(name)
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if @@registry.key? name
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@@registry[name]
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else
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body = new(name)
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@@registry[name] = body
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end
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end
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def self.get(name)
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@@registry[name]
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end
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end
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def parse(input)
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input.lines.map do |line|
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center_name, satellite_name = line.strip.split(')')
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center = Body.get_or_create center_name
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satellite = Body.get_or_create satellite_name
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center << satellite
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end
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end
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input = File.read(File.join(__dir__, 'input'))
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parse(input)
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def find_path(start, goal)
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queue = [[start.parent]]
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visited = Set.new
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visited << start
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until queue.empty?
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path = queue.shift
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state = path[-1]
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next if visited.include? state
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visited << state
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return path if state.satellites.include? goal
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children = state.satellites
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children << state.parent if state.parent
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children.each do |child|
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queue << path + [child]
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end
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end
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nil
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end
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you = Body.get 'YOU'
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santa = Body.get 'SAN'
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path = find_path(you, santa)
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puts path.length - 1
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