Phone number to letters converter

phone2letters.rb

Letters = {
  '0' => %w(0),
  '1' => %w(1),
  '2' => %w(a b c),
  '3' => %w(d e f),
  '4' => %w(g h i),
  '5' => %w(j k l),
  '6' => %w(m n o),
  '7' => %w(p q r s),
  '8' => %w(t u v),
  '9' => %w(w x y z),
}

def convert(number)
  mapping = number.map { |d| Letters[d] }
  first = mapping.first
  rest = mapping[1..-1]
  first.product(*rest).map { |l| l.join }
end

result = convert %w(5 0 7)
solution = %w(
  j0p j0q j0r j0s
  k0p k0q k0r k0s
  l0p l0q l0r l0s)
puts 'OK' if (solution - result).empty?

result = convert %w(3 6 9)
solution = %w(dmw dmx dmy dmz
              dnw dnx dny dnz
              dow dox doy doz
              emw emx emy emz
              enw enx eny enz
              eow eox eoy eoz
              fmw fmx fmy fmz
              fnw fnx fny fnz
              fow fox foy foz)
puts 'OK' if (solution - result).empty?

# Jednak tak czytelniej jak dla mnie ;]
mapper = {
  '0' => [0],
  '1' => [1],
  '2' => %w(a b c),
  '3' => %w(d e f),
  '4' => %w(g h i),
  '5' => %w(j k l),
  '6' => %w(m n o),
  '7' => %w(p q r s),
  '8' => %w(t u v),
  '9' => %w(w x y z),
}

def convert(phone)
  mapped = phone.map{|l| mapper[l]}
  mapped.shift.product(*mapped).map(&:join)
end