Add Day 7

src/2024/07/Program.cs

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+using System.Buffers;
+using System.ComponentModel.DataAnnotations;
+using System.Globalization;
+
+using ConsoleAppFramework;
+
+var builder = ConsoleApp.Create();
+builder.Add("part-one", static ([Argument, FileExists] string file) =>
+{
+	Console.WriteLine($"Result: {ReadFile(file, true)}");
+});
+builder.Add("part-two", static ([Argument, FileExists] string file) =>
+{
+	Console.WriteLine($"Result: {ReadFile(file, false)}");
+});
+builder.Run(args);
+
+static long ReadFile(string file, bool simple)
+{
+	long result = 0;
+	using (var fileReader = new StreamReader(file))
+	{
+		ArrayBufferWriter<long> valueBuffer = new();
+		while (fileReader.ReadLine() is { } line)
+		{
+			valueBuffer.ResetWrittenCount();
+			var colon = line.IndexOf(':');
+			var expected = long.Parse(line.AsSpan(0, line.IndexOf(':')));
+			var valueSpan = line.AsSpan(colon + 1).Trim();
+			foreach (var valueRange in valueSpan.Split(' '))
+			{
+				var numberSpan = valueSpan[valueRange];
+				if (numberSpan.IsWhiteSpace())
+				{
+					continue;
+				}
+
+				valueBuffer.GetSpan(1)[0] = int.Parse(numberSpan, NumberStyles.None);
+				valueBuffer.Advance(1);
+			}
+
+			var values = valueBuffer.WrittenSpan;
+			if (IsValid(expected, values[..1], values[1..]))
+			{
+				result = checked(result + expected);
+			}
+		}
+	}
+
+	return result;
+
+	bool IsValid(long expected, ReadOnlySpan<long> results, in ReadOnlySpan<long> values)
+	{
+		if (values.Length == 0)
+		{
+			return results.Contains(expected);
+		}
+
+		var optionLength = simple ? 2 : 3;
+		var newResults = new long[results.Length * optionLength];
+		var factor = values[0];
+		var factorPow10 = (int)Math.Pow(10, (int)Math.Floor(Math.Log10(factor) + 1));
+
+		for (int i = 0; i < results.Length; i++)
+		{
+			var value = results[i];
+			((ReadOnlySpan<long>)[value + factor, value * factor]).CopyTo(newResults.AsSpan(i * optionLength, 2));
+			if (!simple)
+			{
+				newResults[i * optionLength + 2] = value * factorPow10 + factor;
+			}
+		}
+
+		return IsValid(expected, newResults, values[1..]);
+	}
+}
+
+class FileExistsAttribute : ValidationAttribute
+{
+	public override bool IsValid(object? value) => value is string path && File.Exists(path);
+}

src/2024/07/aoc-2024-07.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <RootNamespace>aoc_2024_07</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>