Adjacent number algorithm grouper

Question

By which I mean this:

Given the input set of numbers:

1,2,3,4,5 becomes \"1-5\".

1,2,3,5,7,9,10,11,12,14 becomes \"1-3, 5, 7, 9-12, 14\"

This is

Answer 1

Short and sweet Ruby

def range_to_s(range)
  return range.first.to_s if range.size == 1
  return range.first.to_s + "-" + range.last.to_s
end

def format_ints(ints)
  range = []
  0.upto(ints.size-1) do |i|
    range << ints[i]
    unless (range.first..range.last).to_a == range
      return range_to_s(range[0,range.length-1]) + "," + format_ints(ints[i,ints.length-1])
    end
  end
  range_to_s(range)  
end