115 lines
4.8 KiB
Markdown
115 lines
4.8 KiB
Markdown
# 2019 Day 14: Space Stoichiometry
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Copyright (c) Eric Wastl
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#### [Direct Link](https://adventofcode.com/2019/day/14)
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## Part 1
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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.
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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.
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You just need to know how much **`ORE`** you'll need to collect before you can produce one unit of **`FUEL`**.
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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`.
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Suppose your nanofactory produces the following list of reactions:
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```
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10 ORE => 10 A
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1 ORE => 1 B
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7 A, 1 B => 1 C
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7 A, 1 C => 1 D
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7 A, 1 D => 1 E
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7 A, 1 E => 1 FUEL
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```
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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.)
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Or, suppose you have the following list of reactions:
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```
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9 ORE => 2 A
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8 ORE => 3 B
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7 ORE => 5 C
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3 A, 4 B => 1 AB
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5 B, 7 C => 1 BC
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4 C, 1 A => 1 CA
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2 AB, 3 BC, 4 CA => 1 FUEL
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```
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The above list of reactions requires **165** `ORE` to produce 1 `FUEL`:
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- Consume 45 `ORE` to produce 10 `A`.
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- Consume 64 `ORE` to produce 24 `B`.
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- Consume 56 `ORE` to produce 40 `C`.
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- Consume 6 `A`, 8 `B` to produce 2 `AB`.
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- Consume 15 `B`, 21 `C` to produce 3 `BC`.
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- Consume 16 `C`, 4 `A` to produce 4 `CA`.
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- Consume 2 `AB`, 3 `BC`, 4 `CA` to produce 1 `FUEL`.
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Here are some larger examples:
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- **13312** `ORE` for 1 `FUEL`:
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```
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157 ORE => 5 NZVS
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165 ORE => 6 DCFZ
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44 XJWVT, 5 KHKGT, 1 QDVJ, 29 NZVS, 9 GPVTF, 48 HKGWZ => 1 FUEL
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12 HKGWZ, 1 GPVTF, 8 PSHF => 9 QDVJ
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179 ORE => 7 PSHF
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177 ORE => 5 HKGWZ
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7 DCFZ, 7 PSHF => 2 XJWVT
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165 ORE => 2 GPVTF
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3 DCFZ, 7 NZVS, 5 HKGWZ, 10 PSHF => 8 KHKGT
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```
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- **180697** ORE for 1 FUEL:
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```
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2 VPVL, 7 FWMGM, 2 CXFTF, 11 MNCFX => 1 STKFG
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17 NVRVD, 3 JNWZP => 8 VPVL
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53 STKFG, 6 MNCFX, 46 VJHF, 81 HVMC, 68 CXFTF, 25 GNMV => 1 FUEL
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22 VJHF, 37 MNCFX => 5 FWMGM
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139 ORE => 4 NVRVD
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144 ORE => 7 JNWZP
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5 MNCFX, 7 RFSQX, 2 FWMGM, 2 VPVL, 19 CXFTF => 3 HVMC
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5 VJHF, 7 MNCFX, 9 VPVL, 37 CXFTF => 6 GNMV
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145 ORE => 6 MNCFX
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1 NVRVD => 8 CXFTF
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1 VJHF, 6 MNCFX => 4 RFSQX
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176 ORE => 6 VJHF
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```
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- **2210736** ORE for 1 FUEL:
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```
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171 ORE => 8 CNZTR
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7 ZLQW, 3 BMBT, 9 XCVML, 26 XMNCP, 1 WPTQ, 2 MZWV, 1 RJRHP => 4 PLWSL
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114 ORE => 4 BHXH
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14 VRPVC => 6 BMBT
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6 BHXH, 18 KTJDG, 12 WPTQ, 7 PLWSL, 31 FHTLT, 37 ZDVW => 1 FUEL
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6 WPTQ, 2 BMBT, 8 ZLQW, 18 KTJDG, 1 XMNCP, 6 MZWV, 1 RJRHP => 6 FHTLT
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15 XDBXC, 2 LTCX, 1 VRPVC => 6 ZLQW
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13 WPTQ, 10 LTCX, 3 RJRHP, 14 XMNCP, 2 MZWV, 1 ZLQW => 1 ZDVW
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5 BMBT => 4 WPTQ
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189 ORE => 9 KTJDG
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1 MZWV, 17 XDBXC, 3 XCVML => 2 XMNCP
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12 VRPVC, 27 CNZTR => 2 XDBXC
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15 KTJDG, 12 BHXH => 5 XCVML
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3 BHXH, 2 VRPVC => 7 MZWV
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121 ORE => 7 VRPVC
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7 XCVML => 6 RJRHP
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5 BHXH, 4 VRPVC => 5 LTCX
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```
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Given the list of reactions in your puzzle input, **what is the minimum amount of `ORE` required to produce exactly 1 `FUEL`**?
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## Part 2
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After collecting `ORE` for a while, you check your cargo hold: **1 trillion** (**1000000000000**) units of `ORE`.
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**With that much ore**, given the examples above:
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- The 13312 `ORE`-per-`FUEL` example could produce **82892753** `FUEL`.
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- The 180697 `ORE`-per-`FUEL` example could produce **5586022** `FUEL`.
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- The 2210736 `ORE`-per-`FUEL` example could produce **460664** `FUEL`.
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Given 1 trillion `ORE`, **what is the maximum amount of FUEL you can produce**? |