48 lines
1.5 KiB
C#
48 lines
1.5 KiB
C#
namespace AOC2016;
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/// <summary>
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/// Day 4: <a href="https://adventofcode.com/2016/day/4"/>
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/// </summary>
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public sealed class Day04() : Day(2016, 4, "Security Through Obscurity")
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{
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private List<Room> _rooms = null!;
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private record Room(string Name, int SectorId, string Checksum)
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{
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public static Room FromRawLine(string raw)
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{
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var s = raw.Split('[');
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var s2 = s[0].Split('-');
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return new(string.Join("", s2[..^1]).Replace("-", string.Empty), int.Parse(s2.Last()), s[1].TrimEnd(']'));
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}
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public bool IsRealRoom() =>
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Name.GroupBy(c => c)
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.OrderByDescending(c => c.Count())
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.ThenBy(c => c.Key)
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.Take(5)
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.Select(c => c.Key)
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.ToArray()
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.SequenceEqual(Checksum.ToCharArray());
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public string DecryptedName()
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{
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var answer = Name.ToCharArray();
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for (var i = 0; i < Name.Length; i++)
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for (var l = 0; l < SectorId % 26; l++)
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answer[i] = answer[i] == 'z' ? 'a' : (char)(answer[i] + 1);
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return new(answer);
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}
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}
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public override void ProcessInput() =>
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_rooms = Input.Select(Room.FromRawLine).ToList();
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public override object Part1() =>
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_rooms.Where(r => r.IsRealRoom()).Sum(r => r.SectorId);
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public override object Part2() =>
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_rooms.Single(r => r.DecryptedName().Contains("northpole")).SectorId;
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}
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