feat: work on day 11 part 1

11/PlutonianPebbles.Tests/ObserverTests.cs

@@ -0,0 +1,25 @@
+namespace PlutonianPebbles.Tests;
+
+public class ObserverTests
+{
+  private static readonly string[] ExampleInput = ["125", "17"];
+  
+  [Test]
+  [MethodDataSource(nameof(BlinkTestCases))]
+  public async Task Blink_WhenCalled_ItShouldReturnExpectedValue(BlinkTestCase testCase)
+  {
+    var stones = testCase.Stones.Select(Stone.From).ToList();
+    var observer = Observer.Of(stones);
+
+    var result = observer.Blink(testCase.NumberOfBlinks);
+
+    await Assert.That(result).IsEqualTo(testCase.ExpectedLineOfStones);
+  }
+
+  public static IEnumerable<Func<BlinkTestCase>> BlinkTestCases()
+  {
+    yield return () => new(ExampleInput, 0, "125 17");
+  }
+
+  public record BlinkTestCase(string[] Stones, int NumberOfBlinks, string ExpectedLineOfStones);
+}

11/PlutonianPebbles.Tests/StoneTests.cs

@@ -0,0 +1,36 @@
+namespace PlutonianPebbles.Tests;
+
+public class StoneTests
+{
+  [Test]
+  public async Task ToString_WhenCalled_ItShouldReturnEngravedValue()
+  {
+    var engravedValue = "0";
+    
+    var result = Stone.From(engravedValue).ToString();
+
+    await Assert.That(result).IsEqualTo(engravedValue);
+  }
+  
+  [Test]
+  [MethodDataSource(nameof(TransformTestCases))]
+  public async Task Transform_WhenCalled_ItShouldReturnStonedWithExpectedEngraving(TransformTestCase testCase)
+  {
+    var expected = testCase.TransformedValues.Select(Stone.From).ToList();
+    
+    var result = Stone.From(testCase.EngravedValue).Transform();
+
+    await Assert.That(result).IsEquivalentTo(expected);
+  }
+  
+  public static IEnumerable<Func<TransformTestCase>> TransformTestCases()
+  {
+    yield return () => new("0", ["1"]);
+    yield return () => new("1", ["2024"]);
+    yield return () => new("10", ["1", "0"]);
+    yield return () => new("99", ["9", "9"]);
+    yield return () => new("999", ["2021976"]);
+  }
+  
+  public record TransformTestCase(string EngravedValue, List<string> TransformedValues);
+}

11/PlutonianPebbles/Program.cs

@@ -13,12 +13,81 @@ if (File.Exists(args[0]) is false)
 }
 
 var isPart2 = args.Length is 2 && args[1] is "part2";
-var input = await File.ReadAllLinesAsync(args[0]);
+var input = await File.ReadAllTextAsync(args[0]);
 
 var stopwatch = new Stopwatch();
 stopwatch.Start();
 
-// TODO: Implement solution
+var stones = input
+  .Split(" ", StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)
+  .Select(Stone.From)
+  .ToList();
+
+var observer = Observer.Of(stones);
+
+var result = observer.Blink(25);
 
 stopwatch.Stop();
 Console.WriteLine($". ({stopwatch.ElapsedMilliseconds}ms)");
+
+class Observer
+{
+  private readonly List<Stone> _stones;
+
+  private Observer(List<Stone> stones)
+  {
+    _stones = stones;
+  }
+
+  public static Observer Of(List<Stone> stones) => new(stones);
+
+  public string Blink(int times)
+  {
+    if (times < 1)
+    {
+      return string.Join(" ", _stones);
+    }
+    
+    return string.Empty;
+  }
+}
+
+record Stone
+{
+  private readonly string _engravedValue;
+
+  private Stone(string engravedValue)
+  {
+    _engravedValue = engravedValue;
+  }
+
+  public static Stone From(string engraving) => new(engraving);
+
+  public List<Stone> Transform()
+  {
+    if (_engravedValue is "0")
+    {
+      return [new Stone("1")];
+    }
+
+    var hasOddNumberOfDigits = _engravedValue.Length % 2 is not 0;
+
+    if (hasOddNumberOfDigits)
+    {
+      var engravedNumber = int.Parse(_engravedValue);
+      var newEngravedValue = engravedNumber * 2024;
+      return [new(newEngravedValue.ToString())];
+    }
+
+    var middleIndex = _engravedValue.Length / 2;
+    var leftDigits = _engravedValue[..middleIndex].TrimStart('0');
+    var rightDigits = _engravedValue[middleIndex..].TrimStart('0');
+
+    return [new(leftDigits), new(rightDigits)];
+  }
+
+  public override string ToString()
+  {
+    return _engravedValue;
+  }
+}