How can I print out all possible letter combinations a given phone number can represent?

Question

I just tried for my first programming interview and one of the questions was to write a program that given a 7 digit telephone number, could print all possible combinations

Answer 1

I tried it in ruby, and came up with a different way of doing, it's probably not efficient, like time and space O(?) at this point, but I like it because it uses Ruby's builtin Array.product method. What do you think?

EDIT: I see a very similar solution in Python above, but I hadn't seen it when I added my answer

def phone_to_abc(phone)

  phone_abc = [
    '0', '1', 'abc', 'def', 'ghi',
    'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'
  ]

  phone_map = phone.chars.map { |x| phone_abc[x.to_i].chars }
  result = phone_map[0]
  for i in 1..phone_map.size-1
    result = result.product(phone_map[i])
  end
  result.each { |x|
    puts "#{x.join}"
  }

end

phone_to_abc('86352')