push the next biggest file onto the smallest partition until no more files

gistfile1.rb

partitions.min_by { |p| p.inject(0) { |combined_weight, file| combined_weight + file_weights[file] } }
  .push(files_biggest_first.delete_at(0)) until files_biggest_first.empty?

partition.rb

#!/usr/bin/env ruby
# usage: partition.rb PATTERN N K [WEIGHTS]
#
# splits files matching PATTERN into N partitions, and outputs the Kth one
#
# WEIGHTS is an optional .yml file that contains weights for each file
# If present, we attempt to minimize the combined weight of the largest partition

require 'yaml'

pattern = ARGV[0]
n, k = ARGV[1, 2].map(&:to_i)
weights = ARGV[3]

files = Dir.glob(pattern)

if weights && File.exists?(weights)
  file_weights = Hash.new(0).merge(YAML.load_file(weights)) # 0 is default value
  files_biggest_first = files.sort { |f1, f2| file_weights[f1] <=> file_weights[f2] }.reverse!
  partitions = Array.new(n) { [] }
  partitions.min_by { |p| p.inject(0) { |combined_weight, file| combined_weight + file_weights[file] } }
    .push(files_biggest_first.delete_at(0)) until files_biggest_first.empty?
  puts partitions[k-1]
else
  size = (files.length.to_f / n).ceil
  puts files[(k - 1) * size, size]
end

Slick.