love a good ugly sweater puzzle

Author: robbkidd

2025/ruby/day07.rb

@@ -0,0 +1,111 @@
+require_relative 'day'
+require_relative 'grid'
+require_relative 'ugly_sweater'
+
+class Day07 < Day # >
+
+  # @example
+  #   day.part1 #=> 21
+  def part1
+    @tachy = TachyonManifold.new(input).parse
+    @tachy.track_beam
+    puts "\n" + @tachy.to_s if ENV['DEBUG']
+    @tachy.beam_splits
+  end
+
+  # @example
+  #   day.part1
+  #   day.part2 #=> 40
+  def part2
+    @tachy.timeline_splits
+  end
+
+  EXAMPLE_INPUT = File.read("../inputs/day07-example-input.txt")
+end
+
+class TachyonManifold < Grid
+  include UglySweater
+
+  attr_reader :entrance, :splitter_coords, :splitters_by_row, :beams_by_row
+
+  def self.example
+    new(Day07::EXAMPLE_INPUT).parse
+  end
+
+  def initialize(input=nil)
+    super
+    @entrance = nil
+    @splitter_coords = Set.new
+  end
+
+  # @example
+  #   tachmani = new(Day07::EXAMPLE_INPUT)
+  #   tachmani.parse
+  #   tachmani.entrance #=> [0,7]
+  #   tachmani.splitter_coords #=> Set[[2, 7], [4, 6], [4, 8], [6, 5], [6, 7], [6, 9], [8, 4], [8, 6], [8, 10], [10, 3], [10, 5], [10, 9], [10, 11], [12, 2], [12, 6], [12, 12], [14, 1], [14, 3], [14, 5], [14, 7], [14, 9], [14, 13]]
+  #   tachmani.splitters_by_row[4] #=> Set[6,8]
+  #   tachmani.beams_by_row[0] #=> Set[7]
+  def parse
+    super { |coord, char|
+      case char
+      when "S" ; @entrance = coord
+      when "^" ; @splitter_coords << coord
+      else ; # keep calm and parse on
+      end
+    }
+
+    @beams_by_row = Array.new(@row_bounds.count) { Set.new }
+    @beams_by_row[@entrance[0]] << @entrance[1]
+
+    @beam_density = Hash.new { 0 }
+    @beam_density[@entrance] += 1
+
+    @splitters_by_row = Array.new(@row_bounds.count) { Set.new }
+    @splitter_coords.each { |(r,c)|
+      @splitters_by_row[r] << c
+    }
+
+    @beam_splits = 0
+
+    self
+  end
+
+  def track_beam
+    @row_bounds.to_a[1..].each { |r|
+      @beams_by_row[r-1].each { |c|
+        if @splitters_by_row[r].include?(c)
+          @beams_by_row[r] << c-1
+          @beams_by_row[r] << c+1
+          @beam_splits += 1
+          @beam_density[[r,c-1]] += @beam_density[[r-1,c]]
+          @beam_density[[r,c+1]] += @beam_density[[r-1,c]]
+        else
+          @beams_by_row[r] << c
+          @beam_density[[r,c]] += @beam_density[[r-1,c]]
+        end
+      }
+    }
+  end
+
+  def beam_splits
+    @beam_splits
+  end
+
+  def timeline_splits
+    @beam_density
+      .filter_map {|(r,c), density| density if r == @row_bounds.max }
+      .reduce(&:+)
+  end
+
+  def to_s
+    super { |(r,c), char|
+      case
+      when char == "S" ; char.make_it_green
+      when @splitter_coords.include?([r,c]) ; char.make_it_red.make_it_bold
+      when @beam_density[[r,c]] > 0 ; "|".make_it_green
+      else ; char
+      end
+    }
+  end
+
+end

2025/ruby/ugly_sweater.rb

@@ -0,0 +1,39 @@
+module UglySweater
+  String.prepend(
+    Module.new do
+      def make_it_red
+        "\e[41m#{self.delete_suffix("\e[0m")}\e[0m"
+      end
+      def make_it_green
+        "\e[32m#{self.delete_suffix("\e[0m")}\e[0m"
+      end
+      def make_it_bold
+        "\e[1m#{self.delete_suffix("\e[0m")}\e[0m"
+      end
+    end
+  )
+  # for use with outputs that are periods and octothorps
+  def self.ugly_christmas_sweater(output = "")
+    output.gsub(/#/, make_it_red("#")).gsub(/\./, make_it_green("."))
+  end
+
+  def ugly_christmas_sweater(output)
+    self.class.ugly_christmas_sweater(output)
+  end
+
+  def self.make_it_red(s, bold: false)
+    "\e[41m\e[1m#{s}\e[0m"
+  end
+
+  def self.make_it_green(s)
+    "\e[32m#{s}\e[0m"
+  end
+
+  def self.clear_codes
+    "\e[H\e[2J"
+  end
+
+  def clear_codes
+    self.class.clear_codes
+  end
+end