feat: solved day 11 part 1 and part 2

11/PlutonianPebbles.Tests/ObserverTests.cs

@@ -3,6 +3,54 @@
 public class ObserverTests
 {
   private static readonly string[] ExampleInput = ["125", "17"];
+
+  private async Task<string> GetPuzzleInput()
+  {
+    return await File.ReadAllTextAsync(Path.Combine(AppContext.BaseDirectory, "INPUT.txt"));
+  }
+  
+  [Test]
+  public async Task Blink_WhenCalledWithPuzzleInputAnd25Times_ItShouldReturnCorrectNumberOfStones()
+  {
+    var input = await GetPuzzleInput();
+    var stones = input
+      .Split(" ", StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)
+      .Select(Stone.From)
+      .ToList();
+    
+    var observer = Observer.Of(stones);
+
+    var result = observer.Blink(25);
+
+    await Assert.That(result).IsEqualTo(191690);
+  }
+  
+  [Test]
+  public async Task Blink_WhenCalledWithPuzzleInputAnd75Times_ItShouldReturnCorrectNumberOfStones()
+  {
+    var input = await GetPuzzleInput();
+    var stones = input
+      .Split(" ", StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)
+      .Select(Stone.From)
+      .ToList();
+    
+    var observer = Observer.Of(stones);
+
+    var result = observer.Blink(75);
+
+    await Assert.That(result).IsEqualTo(228651922369703);
+  }
+  
+  [Test]
+  public async Task Blink_WhenCalledWithExampleInputAnd25Times_ItShouldReturnCorrectNumberOfStones()
+  {
+    var stones = ExampleInput.Select(Stone.From).ToList();
+    var observer = Observer.Of(stones);
+
+    var result = observer.Blink(25);
+
+    await Assert.That(result).IsEqualTo(55312);
+  }
   
   [Test]
   [MethodDataSource(nameof(BlinkTestCases))]
@@ -12,14 +60,20 @@ public class ObserverTests
     var observer = Observer.Of(stones);
 
     var result = observer.Blink(testCase.NumberOfBlinks);
-
-    await Assert.That(result).IsEqualTo(testCase.ExpectedLineOfStones);
+    
+    await Assert.That(result).IsEqualTo(testCase.ExpectedNumberOfStones);
   }
 
   public static IEnumerable<Func<BlinkTestCase>> BlinkTestCases()
   {
-    yield return () => new(ExampleInput, 0, "125 17");
+    yield return () => new(ExampleInput, 0, 2);
+    yield return () => new(ExampleInput, 1, 3);
+    yield return () => new(ExampleInput, 2, 4);
+    yield return () => new(ExampleInput, 3, 5);
+    yield return () => new(ExampleInput, 4, 9);
+    yield return () => new(ExampleInput, 5, 13);
+    yield return () => new(ExampleInput, 6, 22);
   }
 
-  public record BlinkTestCase(string[] Stones, int NumberOfBlinks, string ExpectedLineOfStones);
+  public record BlinkTestCase(string[] Stones, int NumberOfBlinks, long ExpectedNumberOfStones);
 }

11/PlutonianPebbles/Observer.cs

@@ -0,0 +1,45 @@
+namespace PlutonianPebbles;
+
+class Observer
+{
+  private readonly List<Stone> _stones;
+
+  private Observer(List<Stone> stones)
+  {
+    _stones = stones;
+  }
+
+  public static Observer Of(List<Stone> stones) => new(stones);
+  
+  public long Blink(int times)
+  {
+    var stoneCounts = _stones.GroupBy(s => s)
+      .ToDictionary(g => g.Key, g => (long)g.Count());
+    
+    for (var blinks = 0; blinks < times; blinks++)
+    {
+      var nextCounts = new Dictionary<Stone, long>();
+      
+      foreach (var (stone, count) in stoneCounts)
+      {
+        var transformed = stone.Transform();
+
+        foreach (var result in transformed)
+        {
+          if (nextCounts.ContainsKey(result))
+          {
+            nextCounts[result] += count;
+          }
+          else
+          {
+            nextCounts[result] = count;
+          }
+        }
+      }
+
+      stoneCounts = nextCounts;
+    }
+    
+    return stoneCounts.Values.Sum();
+  }
+}

11/PlutonianPebbles/Program.cs

@@ -1,5 +1,7 @@
 using System.Diagnostics;
 
+using PlutonianPebbles;
+
 if (args.Length is 0)
 {
   Console.WriteLine("Please provide a path to the input file.");
@@ -25,69 +27,9 @@ var stones = input
 
 var observer = Observer.Of(stones);
 
-var result = observer.Blink(25);
+var times = isPart2 ? 75 : 25;
+
+var result = observer.Blink(times);
 
 stopwatch.Stop();
-Console.WriteLine($". ({stopwatch.ElapsedMilliseconds}ms)");
-
-class Observer
-{
-  private readonly List<Stone> _stones;
-
-  private Observer(List<Stone> stones)
-  {
-    _stones = stones;
-  }
-
-  public static Observer Of(List<Stone> stones) => new(stones);
-
-  public string Blink(int times)
-  {
-    if (times < 1)
-    {
-      return string.Join(" ", _stones);
-    }
-    
-    return string.Empty;
-  }
-}
-
-record Stone
-{
-  private readonly string _engravedValue;
-
-  private Stone(string engravedValue)
-  {
-    _engravedValue = engravedValue;
-  }
-
-  public static Stone From(string engraving) => new(engraving);
-
-  public List<Stone> Transform()
-  {
-    if (_engravedValue is "0")
-    {
-      return [new Stone("1")];
-    }
-
-    var hasOddNumberOfDigits = _engravedValue.Length % 2 is not 0;
-
-    if (hasOddNumberOfDigits)
-    {
-      var engravedNumber = int.Parse(_engravedValue);
-      var newEngravedValue = engravedNumber * 2024;
-      return [new(newEngravedValue.ToString())];
-    }
-
-    var middleIndex = _engravedValue.Length / 2;
-    var leftDigits = _engravedValue[..middleIndex].TrimStart('0');
-    var rightDigits = _engravedValue[middleIndex..].TrimStart('0');
-
-    return [new(leftDigits), new(rightDigits)];
-  }
-
-  public override string ToString()
-  {
-    return _engravedValue;
-  }
-}
+Console.WriteLine($"The number of stones is {result}. ({stopwatch.ElapsedMilliseconds}ms)");

11/PlutonianPebbles/Stone.cs

@@ -0,0 +1,41 @@
+namespace PlutonianPebbles;
+
+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 = long.Parse(_engravedValue);
+      var newEngravedValue = engravedNumber * 2024;
+      return [new(newEngravedValue.ToString())];
+    }
+
+    var middleIndex = _engravedValue.Length / 2;
+    var leftDigits = long.Parse(_engravedValue[..middleIndex]);
+    var rightDigits = long.Parse(_engravedValue[middleIndex..]);
+    
+    return [new(leftDigits.ToString()), new(rightDigits.ToString())];
+  }
+
+  public override string ToString()
+  {
+    return _engravedValue;
+  }
+}

README.md

@@ -54,3 +54,4 @@ dotnet build
 | 08  | [Problem](./08/PROBLEM.md) | [Solution](./08/ResonantCollinearity/) | Without some help from chat I don't know where I'd be...to be fair the description kind of mislead me. |
 | 09  | [Problem](./09/PROBLEM.md) | [Solution](./09/DiskFragmenter/)       | Doing things with indexes is error prone.                                                              |
 | 10  | [Problem](./10/PROBLEM.md) | [Solution](./10/HoofIt/)               | I recognized the solution for this based on pattern from last year. Solved using BFS.                  |
+| 11  | [Problem](./11/PROBLEM.md) | [Solution](./11/PlutonianPebbles/)     | Dictionary > List                                                                                      |