How do I summarize array of integers as an array of ranges?

Question

I\'d like to take input such as:

[1,2,4,5,6,7,9,13]

and turn it into something like the following:

[[1,2],[4,7],[9,9],[13,1         


        

Answer 1

Hmm, well, it's not tokland's masterpiece, but I think it may be a good straightforward solution...

[1,2,4,5,6,7,9,13].inject([]) do |m, v|
  if m.last.to_a.last == v.pred
    m[-1][-1] = v
  else
    m << [v, v]
  end
  m
end