108 lines
2.9 KiB
C#
108 lines
2.9 KiB
C#
namespace aoc2019;
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public sealed class Day14 : Day
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{
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private readonly Dictionary<string, Reaction> reactions;
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private Dictionary<string, long> available;
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public Day14() : base(14, "Space Stoichiometry")
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{
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reactions = Input
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.Select(Reaction.Parse)
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.ToDictionary(r => r.product.Name);
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available = new();
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}
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private bool Consume(string chem, long quantity)
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{
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if (quantity <= 0)
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throw new ArgumentOutOfRangeException(nameof(quantity));
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if (!available.ContainsKey(chem))
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available[chem] = 0;
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if (available[chem] < quantity && !Produce(chem, quantity - available[chem]))
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return false;
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available[chem] -= quantity;
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return true;
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}
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private bool Produce(string chem, long quantity)
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{
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if (chem == "ORE")
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return false;
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var reaction = reactions[chem];
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var reactionCount = (long)Math.Ceiling((double)quantity / reaction.product.Quantity);
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foreach (var reactant in reaction.reactants)
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if (!Consume(reactant.Name, reactionCount * reactant.Quantity))
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return false;
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available[chem] = available.GetValueOrDefault(chem) + reactionCount * reaction.product.Quantity;
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return true;
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}
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public override string Part1()
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{
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available = new Dictionary<string, long> { { "ORE", long.MaxValue } };
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Consume("FUEL", 1);
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return $"{long.MaxValue - available["ORE"]}";
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}
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public override string Part2()
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{
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const long capacity = 1_000_000_000_000;
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available = new Dictionary<string, long> { { "ORE", capacity } };
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Consume("FUEL", 1);
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var oreConsumed = capacity - available["ORE"];
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while (Produce("FUEL", Math.Max(1, available["ORE"] / oreConsumed)))
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{
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}
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return $"{available["FUEL"] + 1}";
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}
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private struct Component
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{
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public string Name { get; set; }
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public int Quantity { get; set; }
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}
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private class Reaction
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{
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public readonly Component product;
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public readonly Component[] reactants;
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private Reaction(Component[] reactants, Component product)
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{
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this.reactants = reactants;
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this.product = product;
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}
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public static Reaction Parse(string s)
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{
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var ss = s.Split(new[] { ", ", " => " }, StringSplitOptions.None);
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return new Reaction(
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ss.Take(ss.Length - 1).Select(ParseComponent).ToArray(),
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ParseComponent(ss[^1])
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);
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static Component ParseComponent(string s)
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{
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var spl = s.Split(' ', 2);
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return new Component
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{
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Quantity = int.Parse(spl[0]),
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Name = spl[1]
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};
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}
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}
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}
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}
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