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

An even easier solution than @tokland's very nice one is using chunk_while:

xs.chunk_while { |a, b| a + 1 == b }.map do |seq|
  [seq.first, seq.last]
end

Note: chunk_while was introduced in Ruby 2.3