Day 4 (Part 2)

Day04_2/Day04_2.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Remove="input.txt" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include="input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Tools\Tools.csproj" />
+  </ItemGroup>
+
+</Project>

Day04_2/Program.cs

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+using Tools;
+
+var input = InputTools.ReadAllLines();
+int[] cardCount = new int[input.Length];
+for (int i = 0; i < cardCount.Length; i++)
+{
+    cardCount[i] = 1;
+}
+
+for (int cardId = 0; cardId < input.Length; cardId++)
+{
+    string? line = input[cardId];
+    var parts = line.Split(':');
+    var numbers = parts[1].Split('|');
+    var pickedNumbers = numbers[0]
+        .Split(' ', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
+        .Select(int.Parse)
+        .ToArray();
+    var ourNumbers = numbers[1]
+        .Split(' ', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
+        .Select(int.Parse)
+        .ToArray();
+
+    var matchCount = pickedNumbers.Intersect(ourNumbers).Count();
+
+    for (int i = 0; i < matchCount; i++)
+    {
+        cardCount[cardId + 1 + i] += cardCount[cardId];
+    }
+}
+
+Console.WriteLine(cardCount.Sum());

Day04_2/Properties/launchSettings.json

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+{
+  "profiles": {
+    "Run": {
+      "commandName": "Project"
+    }
+  }
+}