Day 12 part 1 Ruby solution

Author: creideiki

12-1.rb

@@ -0,0 +1,101 @@
+#!/usr/bin/env ruby
+
+require 'numo/narray'
+
+class Map
+  attr_reader :map, :regions
+
+  def initialize(input)
+    @height = input.size
+    @width = input[0].size
+    @map = Numo::UInt8.zeros(@height, @width)
+    @height.times do |y|
+      @width.times do |x|
+        @map[y, x] = input[y][x].codepoints[0]
+      end
+    end
+    @handled = Numo::UInt8.zeros(@height, @width)
+    @regions = nil
+  end
+
+  def flood_fill!(y, x)
+    plant = @map[y, x]
+    region = []
+    queue = [[y, x]]
+    until queue.empty?
+      cell = queue.shift
+      next unless @map[cell[0], cell[1]] == plant
+      next unless @handled[cell[0], cell[1]].zero?
+
+      region << cell
+      @handled[cell[0], cell[1]] = 1
+
+      queue << [cell[0] - 1, cell[1]] if cell[0] > 0
+      queue << [cell[0] + 1, cell[1]] if cell[0] < (@height - 1)
+      queue << [cell[0], cell[1] - 1] if cell[1] > 0
+      queue << [cell[0], cell[1] + 1] if cell[1] < (@width - 1)
+    end
+
+    region
+  end
+
+  def split!
+    @regions = []
+    @height.times do |y|
+      @width.times do |x|
+        next if @handled[y, x] == 1
+
+        @regions << flood_fill!(y, x)
+      end
+    end
+  end
+
+  def score
+    @regions.map do |region|
+      area = region.size
+      perimeter = region.map do |plot|
+        p = 0
+        p += 1 unless region.include? [plot[0] - 1, plot[1]]
+        p += 1 unless region.include? [plot[0] + 1, plot[1]]
+        p += 1 unless region.include? [plot[0], plot[1] - 1]
+        p += 1 unless region.include? [plot[0], plot[1] + 1]
+        p
+      end.sum
+      area * perimeter
+    end.sum
+  end
+
+  def inspect
+    to_s
+  end
+
+  def to_s
+    s = "<#{self.class}:\n"
+    @height.times do |y|
+      @width.times do |x|
+        s << @map[y, x]
+      end
+      s += "\n"
+    end
+    s += "\nUsed:\n"
+    @height.times do |y|
+      @width.times do |x|
+        s << case @handled[y, x]
+             when 0
+               '.'
+             when 1
+               '#'
+             end
+      end
+      s += "\n"
+    end
+    s += "\n"
+    s += "#{@regions.size} regions\n" if @regions
+    s += '>'
+    s
+  end
+end
+
+map = Map.new File.read('12.input').lines.map(&:strip)
+map.split!
+puts map.score