Day 1 (Part 2)

Day01_2/Day01_2.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Remove="input.txt" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include="input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
+</Project>

Day01_2/Program.cs

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+var allDigits = new Dictionary<string, int>()
+{
+    { "one", 1 },
+    { "two", 2 },
+    { "three", 3 },
+    { "four", 4 },
+    { "five", 5 },
+    { "six", 6 },
+    { "seven", 7 },
+    { "eight", 8 },
+    { "nine", 9 },
+};
+
+for (int i = 1; i < 10; i++)
+{
+    allDigits.Add(i.ToString(), i);
+}
+
+long total = 0;
+while (Console.ReadLine() is { } line)
+{
+    var firstIndex = line.Length;
+    var lastIndex = -1;
+    var firstValue = 0;
+    var lastValue = 0;
+
+    foreach (var digit in allDigits)
+    {
+        var index = line.IndexOf(digit.Key);
+        if (index == -1)
+        {
+            continue;
+        }
+
+        if (index < firstIndex)
+        {
+            firstIndex = index;
+            firstValue = digit.Value;
+        }
+
+        index = line.LastIndexOf(digit.Key);
+
+        if (index > lastIndex)
+        {
+            lastIndex = index;
+            lastValue = digit.Value;
+        }
+    }
+
+    var fullNumber = firstValue * 10 + lastValue;
+    total += fullNumber;
+}
+
+Console.WriteLine(total);

Day01_2/Properties/launchSettings.json

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+{
+  "profiles": {
+    "Run": {
+      "commandName": "Project",
+      "commandLineArgs": "< input.txt > output.txt"
+    }
+  }
+}