day14.rb

require 'byebug'

class NanoFactory
  attr_reader :ore_used
  def initialize(reactions_text)
    @ore_used = 0
    @stored_chemicals = Hash.new { |h,k| h[k] = 0 }
    reactions = reactions_text.split("\n")
    @formulas = {}
    reactions.each do |reaction|
      source, result = reaction.split(" => ")
      resultant_chemical = portioned_chemical(result)
      source_chemicals = source.split(', ').collect { |s| portioned_chemical(s) }

      @formulas[resultant_chemical[:name]] = { sources: source_chemicals, produced: resultant_chemical[:amount] }
    end
  end

  def get_chemical(name, amount)
    if name == 'ORE'
      @ore_used += amount
      return 'ORE' # this just says "we're done"
    end
    while @stored_chemicals[name] < amount
      # get_chemicals to produce 'name'
      @stored_chemicals[name] += @formulas[name][:produced]
      @formulas[name][:sources].each do |source_chem|
        get_chemical(source_chem[:name], source_chem[:amount])
      end
    end

    @stored_chemicals[name] -= amount
    name #returning the chemical name like we are returning the chemical from the nanofactory
  end

  def ore_required #hack to reuse failed solution structure
    get_chemical('FUEL', 1)
    @ore_used
  end

private
  def portioned_chemical(string)
    amount, name = string.split(' ')
    {name: name, amount: amount.to_i}
  end
end

if __FILE__ == $0
  factory = NanoFactory.new(DATA.read)

  ore_for_one_fuel = factory.ore_required
  print "Requried ORE for 1 FUEL is: #{ore_for_one_fuel}\n\n"

  one_trillion = 1_000_000_000_000
  approximate_amount = one_trillion / ore_for_one_fuel
  max_fuel = 1
  while factory.ore_used < one_trillion
    chunk =
      if max_fuel < approximate_amount - 100
        (approximate_amount - max_fuel) / 2
      else
        1
      end
    print "Using #{max_fuel}, use #{chunk} more.\n"
    factory.get_chemical('FUEL', chunk)
    max_fuel += chunk
  end
  # subtract 1, because that was the fuel that put us over capacity
  print "\nMax FUEL is: #{max_fuel - 1}\n\n"
end

__END__
118 ORE => 7 GTPZ
6 RNQJN, 4 NQKVW => 4 DTQRC
2 GBXJL => 3 XHBR
4 BPZM => 9 LVDRH
131 ORE => 3 RHBL
2 LFZS => 2 FPRJW
6 GTPZ => 4 VTBTK
8 GPMP, 2 BPNFJ, 3 LFZS => 2 SFGCR
3 GPMP => 4 SPRCM
16 XCDZP, 1 NQKSL => 4 NQKVW
2 BXGD, 3 VJHSV, 1 MGNCW => 8 MGLH
1 XLNTJ => 1 KXBGP
9 PJQWR, 19 NQKVW, 10 GJHWN => 7 ZBGDF
3 VTBTK => 6 CJNQ
12 PJQWR => 1 JNHBR
16 BPZM => 9 MVCH
1 KWPXQ, 1 LVDRH => 6 LFZS
6 VTBTK => 6 XCDZP
1 PZFG, 2 LFZS, 2 CJNQ, 2 FPRJW, 17 MVCH, 7 MGNCW, 26 KXBGP => 6 TBTL
2 DTQRC, 7 NBNLC => 8 BPZM
102 ORE => 3 WNTQ
1 WNTQ => 9 NQKSL
5 XZMH, 1 LPLMR, 13 BXGD => 8 JPFL
1 NQKSL, 6 XCDZP, 2 FCDVQ => 9 GJHWN
6 XZMH => 4 GLDL
23 ZTWR, 4 BPZM => 2 MGNCW
11 GPMP, 19 ZBGDF => 2 XZMH
2 MGNCW, 4 XCDZP, 17 KQLT => 4 VJHSV
1 CJNQ => 7 QHPH
1 RHBL => 8 GBXJL
2 MVCH, 3 KDNT, 6 NBNLC, 26 QHPH, 2 KRKB, 1 MCPDH, 4 XZMH, 6 XHBR => 1 HZMWJ
9 XDLZ => 1 QSXKS
4 GLDL => 6 WJNP
5 MVCH => 3 MCPDH
14 TKGM => 5 LPLMR
1 WVQN => 2 PJQWR
4 KWPXQ => 6 FCDVQ
10 DTQRC, 27 TBTL, 9 HZMWJ, 41 XVGP, 2 TPZFL, 54 WNTQ, 85 RHBL, 5 WCZK, 2 QVSB, 28 SPRCM => 1 FUEL
15 RNQJN, 1 PJQWR, 2 NBNLC => 4 TKGM
126 ORE => 5 WVQN
10 NBNLC => 3 BWMD
2 SFGCR, 1 NQKSL, 1 KRKB => 1 WGQTF
2 MLWN => 5 ZTWR
12 DTQRC, 3 NQKVW, 9 NBNLC => 8 BPNFJ
10 SFGCR, 1 PZFG, 2 ZVFVH, 12 WJNP, 14 WGQTF, 1 JNHBR, 8 FPRJW => 3 QVSB
2 MCPDH => 8 XVGP
19 JPFL => 4 TPZFL
5 GBXJL => 6 MLWN
9 TKGM => 5 KDNT
1 NQKVW, 15 PJQWR => 9 XDLZ
2 QHPH, 2 JNHBR => 1 ZVFVH
189 ORE => 6 KWPXQ
5 KRKB, 3 MGLH => 6 WCZK
3 NBNLC, 8 BWMD => 7 KRKB
1 ZBGDF, 6 XDLZ => 4 GPMP
11 XDLZ, 1 QSXKS => 2 BXGD
2 KRKB, 1 GJHWN => 1 XLNTJ
3 ZTWR => 4 RNQJN
15 FCDVQ, 3 MLWN => 4 NBNLC
1 KDNT, 1 XZMH, 8 BXGD => 1 KQLT
2 WJNP => 3 PZFG