55 lines
1.7 KiB
C#
55 lines
1.7 KiB
C#
namespace AOC2020;
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/// <summary>
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/// Day 7: <see href="https://adventofcode.com/2020/day/7" />
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/// </summary>
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public sealed class Day07 : Day
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{
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private readonly Dictionary<string, IEnumerable<(int Weight, string Name)?>> _rules;
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public Day07() : base(2020, 7, "Handy Haversacks") =>
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_rules = Input
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.Select(rule =>
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{
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var spl = rule.Split(" bags contain ", 2);
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var outer = string.Join(' ', spl[0].Split(' ').Take(2));
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var inner = spl[1].Split(", ").Select(ParseQuantity).Where(i => i != null);
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return (outer, inner);
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})
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.ToDictionary(t => t.outer, t => t.inner);
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private static (int, string)? ParseQuantity(string arg)
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{
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if (arg == "no other bags.") return null;
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var words = arg.Split(' ');
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return (int.Parse(words[0]), string.Join(' ', words[1..3]));
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}
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private int Weight(string node) =>
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1 + _rules[node]
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.Where(i => i.HasValue)
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.Select(i => i!.Value)
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.Sum(i => i.Weight * Weight(i.Name));
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public override string Part1()
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{
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// breadth-first search with Queue
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var start = new Queue<string>(new[] { "shiny gold" });
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var p = new HashSet<string>();
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string node;
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while (true)
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{
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node = start.Dequeue();
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foreach (var (container, contained) in _rules)
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if (contained.Any(i => i.HasValue && i.Value.Name == node) && p.Add(container))
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start.Enqueue(container);
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if (!start.Any()) break;
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}
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return $"{p.Count}";
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}
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public override string Part2() => $"{Weight("shiny gold") - 1}";
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}
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