example command to run
$ time ruby xkcd.rb big.txt
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October 13, 2018 05:23
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| 100 | |
| one,1 | |
| two,2 | |
| three,3 | |
| seven,7 |
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| # frozen_string_literal: true | |
| class Xkcd | |
| ITEM = Struct.new(:name, :cost) | |
| def initialize(filename) | |
| fh = File.open(filename) | |
| @answers = [] | |
| @total = pennies(fh.readline) | |
| @items = fh.each_line.map do |line| | |
| item = line.split(',') | |
| raise 'invalid file' unless item.count == 2 | |
| ITEM.new(item.first, pennies(item.last)) | |
| end | |
| fh.close | |
| end | |
| def run | |
| item_pack([], items.sort_by(&:cost)) | |
| answers.each do |answer| | |
| puts answer.map(&:name).join(', ') | |
| end | |
| end | |
| def item_pack(left, right) | |
| while (curr = right.pop) | |
| sublist = left + [curr] | |
| subtotal = sum(sublist) | |
| next if subtotal > total | |
| @answers << sublist if subtotal == total | |
| item_pack(sublist, right + [curr]) | |
| end | |
| end | |
| attr_reader :answers | |
| private | |
| attr_reader :total, :items | |
| def pennies(value) | |
| value.gsub(/[^0-9]/, '').to_i | |
| end | |
| def sum(items) | |
| items.reduce(0) { |sum, i| sum + i.cost } | |
| end | |
| end | |
| Xkcd.new(ARGV.first).run |
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