Alphabetically sorted numbers

Question

This exercise involves taking an array of numbers and sorting them alphabetically. For example, [1,2,3,4] would return as [4,1,3,2]

I mapped the array first, returning an array of words, then sorted those words using Ruby's built-in sort function. Then, I mapped that array to return an array of integers.

It works, obviously. I want your suggestions and thoughts, different ideas and better ways I could do this in the future.

I know I could one-line the map functions, but thought this is better for readability. Example: alphabeticize = numbers.map {|num| alphas.fetch(:"#{num.to_s}")}.sort

def alphabetic_number_sort(numbers)
  alphas = {"0": "zero", "1": "one", "2": "two", "3": "three", "4": "four", "5": "five", "6": "six", "7": "seven", "8": "eight", "9": "nine", "10": "ten", "11": "eleven", "12": "twelve", "13": "thirteen", "14": "fourteen", "15": "fifteen", "16": "sixteen", "17": "seventeen", "18": "eighteen", "19": "nineteen"}

  alphabeticize = numbers.map do |num|
    alphas.fetch(:"#{num.to_s}")
  end.sort

  sorted_alphabetically = alphabeticize.map do |word|
    alphas.key(word).to_s.to_i
  end

  return sorted_alphabetically
end

p alphabetic_number_sort((0..19).to_a) == [
  8, 18, 11, 15, 5, 4, 14, 9, 19, 1, 7, 17,
  6, 16, 10, 13, 3, 12, 2, 0
]

Answer 1

sort_by cleans this up quite a bit, and avoids the unnecessary conversions to and from strings:

def sort_alphabetically(numbers)
  alphas = %w(zero one two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen)
  .map.with_index {|x,i| [i, x]}.to_h

  numbers.sort_by {|x| alphas[x]}
end

Notes:

1. Point on naming: use a verb, or else a noun describing what the function returns: sort_alphabetically or alphabetically_sorted. I know technically alphabetically_sorted isn't a noun, but I see it as an abbreviation for alphabetically_sorted_list, which is too verbose.

2. If speed matters, you should compute the hash outside the function, so it's only done once.

Answer 2

When defining the alphas hash, I would consider strings to be more appropriate as keys than symbols. That would help eliminate the awkward colon during lookup in alphas.fetch(:"#{num.to_s}").

However, I question the need for a hash at all. Why not write it as an array?

ENGLISH_NUMS = %w(
  zero one two three four five six seven eight nine
  ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen
)

Then, it's a simple matter of using Enumerable#sort_by.

def alphabetic_number_sort(numbers)
  numbers.sort_by { |n| ENGLISH_NUMS[n] }
end

Note that it is common practice to omit the explicit return in Ruby.