feat: solved day 11 part 1 and part 2

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();
+  }
+}