require 'optparse'
require 'etc'

NUMBER_OF_COLUMNS = 3
COLUMN_MARGIN = 3
SIZE_INDENT = 2

def main
  files = Dir.glob('*').sort
  output_ls(files)
end

def output_ls(files)
  number_of_row = (files.size / NUMBER_OF_COLUMNS.to_f)
  max_lengths = make_max_lengths(files, number_of_row)

  (0...number_of_row).each do |row|
    NUMBER_OF_COLUMNS.times do |column|
      index = row + column * number_of_row
      print files[index].ljust(max_lengths[column] + COLUMN_MARGIN) if files[index]
    end
    puts
  end
end

def make_max_lengths(files, number_of_row)
  files.each_slice(number_of_row).to_a.map { _1.map(&:length).max }
end

main