Make space for two-digit days

2019-12-10 08:44:15 -08:00 · 2019-12-10 08:44:15 -08:00 · 07eb60e5e1
commit 07eb60e5e1
parent 0967b498c7
29 changed files with 0 additions and 1584 deletions
--- a/2019/day06/part2.rb
+++ b/2019/day06/part2.rb
@ -0,0 +1,90 @@
+# 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