How to get all diagonal from an array of words in Ruby?

Question

I have an array in Ruby

words = ["horses", "follow", "useful", "offset"]

Reference:

h o r s e s
f o l l o w
u s e f u l
o f f s e t

I want to get a list of all its diagonals like this. Here is want I expect in result:

["o", "uf", "fsf", "hoes", "olfe", "rlut", "sol", "ew", "s"]

Would be helpful if anyone can help me a bit on this. Thanks

Answer 1

Try that:

words = ["horses", "follow", "useful", "offset"]

words.reverse.each_with_index.map{|s,i| " " * i + s }.inject(Array.new(words.size + words.last.size-1,"")) do |a,s| 
  s.chars.each_with_index do |c,i| 
    a[i] = c + a[i]
  end
  a
end.map(&:strip)
# => ["o", "uf", "fsf", "hoes", "olfe", "rlut", "sol", "ew", "s"]

At first words.reverse.each_with_index.map{|s,i| " " * i + s } words.reverse.each_with_index.map{|s,i| " " * i + s } builds array with whitespace offset:

offset
 useful
  follow
   horses

Inject creates array of empty strings and inside main block each string chars are prepended to proper array element