62 lines
1.8 KiB
C#
62 lines
1.8 KiB
C#
namespace AOC2015;
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/// <summary>
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/// Day 18: <a href="https://adventofcode.com/2015/day/18"/>
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/// </summary>
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public sealed class Day18() : Day(2015, 18, "Like a GIF For Your Yard")
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{
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private bool[][]? _lights;
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public override void ProcessInput()
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{
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var input = Input.ToArray();
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_lights = Enumerable.Range(0, 102).Select(_ => new bool[102]).ToArray();
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for (var i = 0; i < 100; i++)
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for (var j = 0; j < 100; j++)
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_lights[i + 1][j + 1] = input[i][j] == '#';
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}
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private static bool[][] DoStep(bool[][] lights)
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{
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var nextGrid = Enumerable.Range(0, 102).Select(_ => new bool[102]).ToArray();
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for (var i = 1; i < 101; i++)
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{
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for (var j = 1; j < 101; j++)
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{
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var activeNeighbors = new[]
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{
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lights[i - 1][j - 1],
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lights[i - 1][j],
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lights[i - 1][j + 1],
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lights[i][j - 1],
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lights[i][j + 1],
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lights[i + 1][j - 1],
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lights[i + 1][j],
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lights[i + 1][j + 1]
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}.Count(n => n);
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nextGrid[i][j] = lights[i][j] ? activeNeighbors is 2 or 3 : activeNeighbors == 3;
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}
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}
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return nextGrid;
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}
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public override object Part1()
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{
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for (var i = 0; i < 100; i++) _lights = DoStep(_lights!);
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return _lights!.Sum(l => l.Count(x => x));
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}
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public override object Part2()
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{
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ProcessInput();
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for (var i = 0; i < 100; i++)
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{
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_lights = DoStep(_lights!);
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_lights[1][1] = _lights[1][100] = _lights[100][1] = _lights[100][100] = true;
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}
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return _lights!.Sum(l => l.Count(x => x));
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}
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} |