day 19

src/aoc/Year2024/Day19.cs

@@ -1,20 +1,52 @@
+using mazharenko.AoCAgent.Generator;
+
 namespace aoc.Year2024;
 
+[BypassNoExamples]
 internal partial class Day19
 {
-    internal partial class Part1
-    {
-        public string Solve(string input)
-        {
-            throw new NotImplementedException();
-        }
-    }
+	public (string[] patterns, string[] designs) Parse(string input)
+	{
+		return Character.Letter.Many().Select(chars => new string(chars))
+			.ManyDelimitedBy(Span.EqualTo(", "))
+			.Block()
+			.ThenBlock(
+				Character.Letter.Many().Select(chars => new string(chars))
+					.Lines()
+			).Parse(input);
+	}
+
+	private static long GetWaysCounts(string[] patterns, string design)
+	{
+		// How many ways to build the 0..i substring of <paramref name="design"/> from <paramref name="patterns"/>
+		var dp = new long[design.Length + 1];
+		dp[0] = 1;
+		for (var i = 1; i <= design.Length; i++)
+		{
+			dp[i] =
+				patterns.Where(pattern =>
+					design.AsSpan(0, i).EndsWith(pattern)
+				).Sum(
+					pattern => dp[i - pattern.Length]
+				);
+		}
+
+		return dp[^1];
+	}
+
+	internal partial class Part1
+	{
+		public int Solve((string[] patterns, string[] designs) input)
+		{
+			return input.designs.Count(design => GetWaysCounts(input.patterns, design) > 0);
+		}
+	}
 
-    internal partial class Part2
-    {
-        public string Solve(string input)
-        {
-            throw new NotImplementedException();
-        }
-    }
+	internal partial class Part2
+	{
+		public long Solve((string[] patterns, string[] designs) input)
+		{
+			return input.designs.Sum(design => GetWaysCounts(input.patterns, design));
+		}
+	}
 }

tests/AoC.Tests/InputTests.cs

@@ -44,5 +44,7 @@ private static IEnumerable<PartInputCaseData> GetCases()
 		yield return new PartInputCaseData(17, 2, "190384113204239");
 		yield return new PartInputCaseData(18, 1, "284");
 		yield return new PartInputCaseData(18, 2, "51,50");
+		yield return new PartInputCaseData(19, 1, "338");
+		yield return new PartInputCaseData(19, 2, "841533074412361");
 	}
 }