refactor into a class to do the maths

Of course my part 1 was too naive for part 2. Refactoring in prep for computing differently.

Author: Robb Kidd

2023/ruby/day11.rb

@@ -6,21 +6,12 @@ class Day11 < Day # >
   # @example
   #   day.part1 #=> 374
   def part1
-    expanded_universe =
-      Grid.new(
-        expand_cosmically(
-          scan(input)
-        )
-      )
+    universe = CosmicExpansion.new(input)
 
-    galaxies = []
-    expanded_universe.parse do |coords, value|
-      galaxies << coords if value == GALAXY
-    end
-
-    galaxies
+    universe
+      .galaxies
       .combination(2)
-      .map { |here, there| expanded_universe.manhattan_distance(here, there) }
+      .map { |here, there| universe.distance_between(here, there) }
       .reduce(&:+)
   end
 
@@ -29,23 +20,73 @@ def part1
   def part2
   end
 
+  EXAMPLE_INPUT = <<~INPUT
+    ...#......
+    .......#..
+    #.........
+    ..........
+    ......#...
+    .#........
+    .........#
+    ..........
+    .......#..
+    #...#.....
+  INPUT
+
+  EXPANDED_INPUT = <<~INPUT
+    ....#........
+    .........#...
+    #............
+    .............
+    .............
+    ........#....
+    .#...........
+    ............#
+    .............
+    .............
+    .........#...
+    #....#.......
+  INPUT
+end
+
+class CosmicExpansion
+  attr_reader :galaxies
+
+  def initialize(input)
+    @input = input
+    @galaxies = []
+    @grid =
+      Grid.new(
+        expand_cosmically(
+          scan(input)
+        )
+      )
+    @grid.parse do |coords, value|
+      galaxies << coords if value == GALAXY
+    end
+  end
+
+  EMPTY_SPACE = '.'
+  GALAXY = '#'
+
+  def distance_between(here, there)
+    @grid.manhattan_distance(here, there)
+  end
 
   # @example
   #   simple_input = "...\n.#.\n...\n"
-  #   day.scan(simple_input) #=> [[".",".","."],[".","#","."],[".",".","."]]
+  #   universe = CosmicExpansion.new(simple_input)
+  #   universe.scan(simple_input) #=> [[".",".","."],[".","#","."],[".",".","."]]
   def scan(image)
     image
       .split("\n")
       .map(&:chars)
   end
 
-  EMPTY_SPACE = '.'
-  GALAXY = '#'
-
   # @example
-  #  scanned_image = day.scan(EXAMPLE_INPUT)
+  #  scanned_image = day.scan(Day11::EXAMPLE_INPUT)
   #  input_expanded = day.expand_cosmically(scanned_image)
-  #  input_expanded #=> day.scan(EXPANDED_INPUT)
+  #  input_expanded #=> day.scan(Day11::EXPANDED_INPUT)
   def expand_cosmically(scanned_image)
     # dupe empty-space rows
     expanded_rows = []
@@ -65,51 +106,8 @@ def expand_cosmically(scanned_image)
       end
 
     # pivot things back around to original orientation
-    # unnecessary for computing distances, but wanted for
-    # visualizing output
+    # gotta get rid of this entirely for part 2, though
     3.times { expanded_columns = expanded_columns.transpose }
     expanded_columns
   end
-
-  # @example simple input
-  #   simple_input = "...\n.#.\n...\n"
-  #   scanned_image = day.scan(simple_input)
-  #   scanned_image #=> [[".",".","."],[".","#","."],[".",".","."]]
-  #   day.display(scanned_image) #=> simple_input
-  # @example example input
-  #   scanned_image = day.scan(EXAMPLE_INPUT)
-  #   day.display(scanned_image) #=> EXAMPLE_INPUT
-  def display(scanned_image)
-    scanned_image
-      .map { |row| row.join('') }
-      .join("\n") + "\n"
-  end
-
-  EXAMPLE_INPUT = <<~INPUT
-    ...#......
-    .......#..
-    #.........
-    ..........
-    ......#...
-    .#........
-    .........#
-    ..........
-    .......#..
-    #...#.....
-  INPUT
-
-  EXPANDED_INPUT = <<~INPUT
-    ....#........
-    .........#...
-    #............
-    .............
-    .............
-    ........#....
-    .#...........
-    ............#
-    .............
-    .............
-    .........#...
-    #....#.......
-  INPUT
 end