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2019: Day 6 Part 2

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Jeremy Kaplan 2019-12-06 09:34:39 -08:00
commit 4c72a5dbf6
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2019/day6/part2.rb Normal file
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# frozen_string_literal: true
require 'set'
class Body
attr_reader :name, :satellites
attr_accessor :parent
def initialize(name)
@name = name
@satellites = []
end
def <<(satellite)
@satellites << satellite
satellite.parent = self
end
def inspect
"<Body #{name}, #{satellites.map(&:name).inspect}>"
end
def to_s
name
end
def direct_orbits
@direct_orbits ||= @satellites.length + @satellites.sum(&:direct_orbits)
end
def indirect_orbits(depth = 0)
@indirect_orbits ||= @satellites.sum do |sat|
depth + sat.indirect_orbits(depth + 1)
end
end
@@registry = {}
def self.get_or_create(name)
if @@registry.key? name
@@registry[name]
else
body = new(name)
@@registry[name] = body
end
end
def self.get(name)
@@registry[name]
end
end
def parse(input)
input.lines.map do |line|
center_name, satellite_name = line.strip.split(')')
center = Body.get_or_create center_name
satellite = Body.get_or_create satellite_name
center << satellite
end
end
input = File.read(File.join(__dir__, 'input'))
parse(input)
def find_path(start, goal)
queue = [[start.parent]]
visited = Set.new
visited << start
until queue.empty?
path = queue.shift
state = path[-1]
next if visited.include? state
visited << state
return path if state.satellites.include? goal
children = state.satellites
children << state.parent if state.parent
children.each do |child|
queue << path + [child]
end
end
nil
end
you = Body.get 'YOU'
santa = Body.get 'SAN'
path = find_path(you, santa)
puts path.length - 1