advent-of-code/2023/ruby/day_11.rb

image = ARGF.readlines(chomp: true).map(&:chars)
empty_rows = image.filter_map.with_index {|row,y| row.all? { _1 == ?. } ? y : nil }
empty_cols = image.transpose.filter_map.with_index {|col,x| col.all? { _1 == ?. } ? x : nil }

galaxies = []
y = x = 0
image.each.with_index do |row, yy|
  x = 0
  row.each.with_index do |elem, xx|
    galaxies << [y,x] if elem == ?#
    x += 1
    x += 999_999 if empty_cols.include?(xx)
  end

  y += 1
  y += 999_999 if empty_rows.include?(yy)
end

p galaxies.combination(2).sum {|a, b|
  a.zip(b).sum { (_1 - _2).abs }
}

# original part one

# image = ARGF.read
# image.gsub!(/^(\.+)$/m, "\\1\n\\1")
# image = image.split("\n").map(&:chars).transpose.map(&:join).join("\n")
# image.gsub!(/^(\.+)$/m, "\\1\n\\1")
# image = image.split("\n").map(&:chars)

# galaxies = image.flat_map.with_index {|row, y|
#   row.filter_map.with_index {|elem, x| elem == ?# ? [y,x] : nil }
# }

# p galaxies.combination(2).sum {|a, b|
#   a.zip(b).sum { (_1 - _2).abs }
# }