implementation of flood fill algorithm

floor_plan.rb

class FloorPlan
  attr_reader :input, :layout, :rows, :cols

  EMPTY   = '.'
  VISITED = '-'

  def initialize(file)
    @input  = format(file)
    @layout = format(file)
    @rows   = @layout.size
    @cols   = @layout[0].size
  end

  def rooms
    @rooms ||= count_rooms
  end

  def display
    input.map { |row| row.join }.join("\n")
  end

  private

  def count_rooms
    count = 0
    each { |r,c| count += 1 if floodfill(r,c,EMPTY, VISITED) }
    # minus 1 since the area outside of all rooms counts as a “room”
    count - 1  
  end

  def floodfill(x, y, old_sym, new_sym)
    return unless valid?(x,y) && layout[x][y] == old_sym
    layout[x][y] = new_sym
    floodfill(x+1, y, old_sym, new_sym)
    floodfill(x-1, y, old_sym, new_sym)
    floodfill(x, y+1, old_sym, new_sym)
    floodfill(x, y-1, old_sym, new_sym)
    true
  end

  def format(file)
    open(file, 'r') { |f| f.read }.split.map(&:chars)
  end

  def each(&block)
    layout.each_with_index do |row, r|
      row.each_index { |c| block.call(r,c) }
    end
  end

  def valid?(x,y)
    x.between?(0, rows-1) && 
    y.between?(0, cols-1)
  end
end


display = ->(msg, file) do
  puts msg
  puts '------------'
  fp = FloorPlan.new(file)
  puts "# of rooms: #{fp.rooms}"
  puts fp.display
  print "\n\n"
end

display["Floor Plan 1", 'fp_1.txt']
display["Floor Plan 2", 'fp_2.txt']
display["Floor Plan 3", 'fp_3.txt']
display["Floor Plan 4", 'fp_4.txt']

fp_1.txt

........................#.....
........................#.....
........................#.....
.....######.............######
.....#....#....######.........
.....#....#....#....#.....#...
.....######....##.###.....#...
................#.#.......####
................#.#...........
######.....######.#######.....
#....#.....#............#.....
###..#.....#............#.....
###..#.....######.#######.....
#....#.....#..................
######.....#..................

fp_2.txt

........................#.....
........................######
........................#.....
.....######.............######
.....#....#....######.........
.....#....#....#....#.....#...
.....######....##.###.....#...
................#.#.......####
................#.#...........
######.....######.#######.....
#....#.....#............#.....
###..#.....#............#.....
###..#.....##############.....
#....#....................####
######....................#...

fp_3.txt

...#..#...
####..#...
......####
......#...
......#...

fp_4.txt

........................#.....
........................#.....
........................#.....
.....######.............######
.....#....#....######.........
.....#....#....#....#.....####
.....######....######.....#...
..........................####
..............................
######.....##############.....
#....#.....#............#.....
######.....#............#.....
#....#.....##############.....
#....#........................
######........................