Advent of Code

--- Day 14: Space Stoichiometry ---

   As you approach the rings of Saturn, your ship's low fuel indicator turns on. There isn't any fuel here, but the rings have
   plenty of raw material. Perhaps your ship's Inter-Stellar Refinery Union brand nanofactory can turn these raw materials into
   fuel.

   You ask the nanofactory to produce a list of the reactions it can perform that are relevant to this process (your puzzle
   input). Every reaction turns some quantities of specific input chemicals into some quantity of an output chemical. Almost
   every chemical is produced by exactly one reaction; the only exception, ORE, is the raw material input to the entire process
   and is not produced by a reaction.

   You just need to know how much ORE you'll need to collect before you can produce one unit of FUEL.

   Each reaction gives specific quantities for its inputs and output; reactions cannot be partially run, so only whole integer
   multiples of these quantities can be used. (It's okay to have leftover chemicals when you're done, though.) For example, the
   reaction 1 A, 2 B, 3 C => 2 D means that exactly 2 units of chemical D can be produced by consuming exactly 1 A, 2 B and 3 C.
   You can run the full reaction as many times as necessary; for example, you could produce 10 D by consuming 5 A, 10 B, and 15
   C.

   Suppose your nanofactory produces the following list of reactions:

 10 ORE => 10 A
 1 ORE => 1 B
 7 A, 1 B => 1 C
 7 A, 1 C => 1 D
 7 A, 1 D => 1 E
 7 A, 1 E => 1 FUEL

   The first two reactions use only ORE as inputs; they indicate that you can produce as much of chemical A as you want (in
   increments of 10 units, each 10 costing 10 ORE) and as much of chemical B as you want (each costing 1 ORE). To produce 1
   FUEL, a total of 31 ORE is required: 1 ORE to produce 1 B, then 30 more ORE to produce the 7 + 7 + 7 + 7 = 28 A (with 2 extra
   A wasted) required in the reactions to convert the B into C, C into D, D into E, and finally E into FUEL. (30 A is produced
   because its reaction requires that it is created in increments of 10.)

   Or, suppose you have the following list of reactions:

 9 ORE => 2 A
 8 ORE => 3 B
 7 ORE => 5 C
 3 A, 4 B => 1 AB
 5 B, 7 C => 1 BC
 4 C, 1 A => 1 CA
 2 AB, 3 BC, 4 CA => 1 FUEL

   The above list of reactions requires 165 ORE to produce 1 FUEL:

     • Consume 45 ORE to produce 10 A.
     • Consume 64 ORE to produce 24 B.
     • Consume 56 ORE to produce 40 C.
     • Consume 6 A, 8 B to produce 2 AB.
     • Consume 15 B, 21 C to produce 3 BC.
     • Consume 16 C, 4 A to produce 4 CA.
     • Consume 2 AB, 3 BC, 4 CA to produce 1 FUEL.

   Here are some larger examples:

     • 13312 ORE for 1 FUEL:

 157 ORE => 5 NZVS
 165 ORE => 6 DCFZ
 44 XJWVT, 5 KHKGT, 1 QDVJ, 29 NZVS, 9 GPVTF, 48 HKGWZ => 1 FUEL
 12 HKGWZ, 1 GPVTF, 8 PSHF => 9 QDVJ
 179 ORE => 7 PSHF
 177 ORE => 5 HKGWZ
 7 DCFZ, 7 PSHF => 2 XJWVT
 165 ORE => 2 GPVTF
 3 DCFZ, 7 NZVS, 5 HKGWZ, 10 PSHF => 8 KHKGT

     • 180697 ORE for 1 FUEL:

 2 VPVL, 7 FWMGM, 2 CXFTF, 11 MNCFX => 1 STKFG
 17 NVRVD, 3 JNWZP => 8 VPVL
 53 STKFG, 6 MNCFX, 46 VJHF, 81 HVMC, 68 CXFTF, 25 GNMV => 1 FUEL
 22 VJHF, 37 MNCFX => 5 FWMGM
 139 ORE => 4 NVRVD
 144 ORE => 7 JNWZP
 5 MNCFX, 7 RFSQX, 2 FWMGM, 2 VPVL, 19 CXFTF => 3 HVMC
 5 VJHF, 7 MNCFX, 9 VPVL, 37 CXFTF => 6 GNMV
 145 ORE => 6 MNCFX
 1 NVRVD => 8 CXFTF
 1 VJHF, 6 MNCFX => 4 RFSQX
 176 ORE => 6 VJHF

     • 2210736 ORE for 1 FUEL:

 171 ORE => 8 CNZTR
 7 ZLQW, 3 BMBT, 9 XCVML, 26 XMNCP, 1 WPTQ, 2 MZWV, 1 RJRHP => 4 PLWSL
 114 ORE => 4 BHXH
 14 VRPVC => 6 BMBT
 6 BHXH, 18 KTJDG, 12 WPTQ, 7 PLWSL, 31 FHTLT, 37 ZDVW => 1 FUEL
 6 WPTQ, 2 BMBT, 8 ZLQW, 18 KTJDG, 1 XMNCP, 6 MZWV, 1 RJRHP => 6 FHTLT
 15 XDBXC, 2 LTCX, 1 VRPVC => 6 ZLQW
 13 WPTQ, 10 LTCX, 3 RJRHP, 14 XMNCP, 2 MZWV, 1 ZLQW => 1 ZDVW
 5 BMBT => 4 WPTQ
 189 ORE => 9 KTJDG
 1 MZWV, 17 XDBXC, 3 XCVML => 2 XMNCP
 12 VRPVC, 27 CNZTR => 2 XDBXC
 15 KTJDG, 12 BHXH => 5 XCVML
 3 BHXH, 2 VRPVC => 7 MZWV
 121 ORE => 7 VRPVC
 7 XCVML => 6 RJRHP
 5 BHXH, 4 VRPVC => 5 LTCX

   Given the list of reactions in your puzzle input, what is the minimum amount of ORE required to produce exactly 1 FUEL?

   Your puzzle answer was 751038.

--- Part Two ---

   After collecting ORE for a while, you check your cargo hold: 1 trillion (1000000000000) units of ORE.

   With that much ore, given the examples above:

     • The 13312 ORE-per-FUEL example could produce 82892753 FUEL.
     • The 180697 ORE-per-FUEL example could produce 5586022 FUEL.
     • The 2210736 ORE-per-FUEL example could produce 460664 FUEL.

   Given 1 trillion ORE, what is the maximum amount of FUEL you can produce?

   Your puzzle answer was 2074843.

   Both parts of this puzzle are complete! They provide two gold stars: **

   At this point, all that is left is for you to admire your Advent calendar.

   If you still want to see it, you can get your puzzle input.

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