day 16

src/aoc/Year2024/Day16.cs

@@ -1,20 +1,107 @@
+using aoc.Common;
+using aoc.Common.Search;
+using MoreLinq;
+
 namespace aoc.Year2024;
 
 internal partial class Day16
 {
-    internal partial class Part1
-    {
-        public string Solve(string input)
-        {
-            throw new NotImplementedException();
-        }
-    }
-
-    internal partial class Part2
-    {
-        public string Solve(string input)
-        {
-            throw new NotImplementedException();
-        }
-    }
+	private readonly Example example = new(
+		"""
+		###############
+		#.......#....E#
+		#.#.###.#.###.#
+		#.....#.#...#.#
+		#.###.#####.#.#
+		#.#.#.......#.#
+		#.#.#####.###.#
+		#...........#.#
+		###.#.#####.#.#
+		#...#.....#.#.#
+		#.#.#.###.#.#.#
+		#.....#...#.#.#
+		#.###.#.#.#.#.#
+		#S..#.....#...#
+		###############
+		""");
+
+	private readonly Example example1 = new(
+		"""
+		#################
+		#...#...#...#..E#
+		#.#.#.#.#.#.#.#.#
+		#.#.#.#...#...#.#
+		#.#.#.#.###.#.#.#
+		#...#.#.#.....#.#
+		#.#.#.#.#.#####.#
+		#.#...#.#.#.....#
+		#.#.#####.#.###.#
+		#.#.#.......#...#
+		#.#.###.#####.###
+		#.#.#...#.....#.#
+		#.#.#.#####.###.#
+		#.#.#.........#.#
+		#.#.#.#########.#
+		#S#.............#
+		#################
+		""");
+
+	public char[,] Parse(string input)
+	{
+		// todo: make it easy to create a map, so that not to filter out new lines?
+		return Character.In('S', '.', '#', 'E').Map().Parse(input);
+	}
+
+	IEnumerable<((V<int> point, V<int> direction) newState, int weight)> Adjacency((V<int> point, V<int> direction) arg, char[,] input)
+	{
+		yield return ((arg.point, arg.direction.RotateCw()), 1000);
+		yield return ((arg.point, arg.direction.RotateCcw()), 1000);
+
+		if (input.At(arg.point) != '#')
+			yield return ((arg.point + arg.direction, arg.direction), 1);
+	}
+
+	internal partial class Part1
+	{
+		public Part1()
+		{
+			Expect(example, 7036);
+			Expect(example1, 11048);
+		}
+
+		public int Solve(char[,] input)
+		{
+			var start = input.AsEnumerable().Single(x => x.element == 'S');
+			var finish = input.AsEnumerable().Single(x => x.element == 'E');
+
+			return Dijkstra.StartWith((start.point, direction: Directions.E))
+				.WithAdjacency(arg => Adjacency(arg, input))
+				.FindTarget(state => state.point == finish.point)
+				.Len;
+		}
+	}
+
+	internal partial class Part2
+	{
+		public Part2()
+		{
+			Expect(example, 45);
+			Expect(example1, 64);
+		}
+
+		public int Solve(char[,] input)
+		{
+			var start = input.AsEnumerable().Single(x => x.element == 'S');
+			var finish = input.AsEnumerable().Single(x => x.element == 'E');
+
+			return Dijkstra.StartWith((start.point, direction: Directions.E))
+				.WithAdjacency(x => Adjacency(x, input))
+				.AllShortestPaths()
+				.FindTarget(x => x.point == finish.point)
+				.SelectMany(path => path.PathList)
+				.Select(item => item.Item.point)
+				.Distinct()
+				.Count();
+		}
+	}
 }