def quick_sort(list)
  
  return [] if list.empty?
  
  parts = list.group_by { |n| n <=> list.first }
  less_parts    = parts[-1] || []
  first        = parts[0]  || []
  greater_parts = parts[1]  || []
  quick_sort(less_parts) + first + quick_sort(greater_parts)

end

p quick_sort [13, 27, 25, 11, 88, 92]