2024 Day08 refactored

smabuk · Dec 8, 2024 · 6482c03 · 6482c03
1 parent d0e548d
commit 6482c03
Showing 1 changed file with 41 additions and 31 deletions.
diff --git a/Solutions/2024/Day08.cs b/Solutions/2024/Day08.cs
@@ -18,78 +18,88 @@ public static void LoadMap(string[] input, Action<string[], bool>? visualise = n
 			.ForEachCell()
 			.Where(c => char.IsAsciiLetterOrDigit(c))
 			.ToLookup(a => a.Value, a => a.Index);
+
 		_map.VisualiseMap([], "Initial", visualise);
 	}
 
 	public static int Part1(string[] _, Action<string[], bool>? visualise = null)
 	{
-		List<Point> antinodes = _antennae.GetAntinodes(Antinodes);
+		List<Point> antinodes = _antennae.GetAntinodes(a => a.Antinodes(_map, start: 1));
 		_map.VisualiseMap(antinodes, "Final", visualise);
 
 		return antinodes.Count;
 	}
 
 	public static int Part2(string[] _, Action<string[], bool>? visualise = null)
 	{
-		List<Point> antinodes = _antennae.GetAntinodes(a => a.ResidentHarmonicAntinodes(_map));
+		List<Point> antinodes = _antennae.GetAntinodes(a => a.Antinodes(_map, start: 0));
 		_map.VisualiseMap(antinodes, "Final", visualise);
 
 		return antinodes.Count;
 	}
 
 	private static List<Point> GetAntinodes(this ILookup<char, Point> antennae, Func<IEnumerable<Point>, IEnumerable<Point>> antinodesFunc)
 	{
-		return [..antennae
+		return [..
+			antennae
 			.Select(a => antennae[a.Key])
 			.Select(antinodesFunc)
 			.SelectMany(antinodes => antinodes)
 			.Distinct()
-			.Where(antinode => _map.IsInBounds(antinode))];
+			];
 	}
 
-	private static IEnumerable<Point> Antinodes(this IEnumerable<Point> locations)
+	private static IEnumerable<Point> Antinodes(this IEnumerable<Point> locations, char[,] map, int start)
 	{
-		foreach (IEnumerable<Point> item in locations.Combinations(2)) {
-			Point a1 = item.First();
-			Point a2 = item.Last();
-			yield return a1 - a2 + a1;
-			yield return a2 - a1 + a2;
+		foreach (IEnumerable<Point> pair in locations.Combinations(2)) {
+			Point antenna1 = pair.First();
+			Point antenna2 = pair.Last();
+
+			for (int n = start; ; n++) {
+				bool allOutOfBounds = true;
+
+				foreach (Point antinode in AntinodesN(antenna1, antenna2, n)) {
+					if (map.IsInBounds(antinode)) {
+						yield return antinode;
+						allOutOfBounds = false;
+					}
+				}
+
+				if (allOutOfBounds || start == 1) {
+					break;
+				}
+			}
 		}
 	}
 
-	private static IEnumerable<Point> ResidentHarmonicAntinodes(this IEnumerable<Point> locations, char[,] map)
+	private static IEnumerable<Point> AntinodesN(Point ant1, Point ant2, int n = 1)
 	{
-		foreach (IEnumerable<Point> item in locations.Combinations(2)) {
-			Point a1 = item.First();
-			Point a2 = item.Last();
-			int i = 0;
-			while (map.IsInBounds(((a1 - a2) * i) + a1)) {
-				yield return ((a1 - a2) * i) + a1;
-				i++;
-			}
-
-			i = 0;
-			while (map.IsInBounds(((a2 - a1) * i) + a2)) {
-				yield return ((a2 - a1) * i) + a2;
-				i++;
-			}
-		}
+		yield return ((ant1 - ant2) * n) + ant1;
+		yield return ((ant2 - ant1) * n) + ant2;
 	}
 
+	// Not needed for AoC input
+	//private static Point AntinodeGcdN(Point ant1, Point ant2, int n = 1)
+	//{
+	//	Point gcd = new(
+	//		0.GreatestCommonDivisor(ant1.X - ant2.X),
+	//		0.GreatestCommonDivisor(ant1.Y - ant2.Y));
+	//	return (gcd * n) + ant1;
+	//}
 
 	public static void VisualiseMap(this char[, ] map, IEnumerable<Point> antinodes, string title, Action<string[], bool>? visualise)
 	{
-		char[,] copy = (char[,])map.Clone();
+		const char ANTINODE = '#';
+
+		char[,] vMap = (char[,])map.Clone();
 
 		foreach (Point antinode in antinodes) {
-			copy[antinode.X, antinode.Y] = ANTINODE;
+			vMap[antinode.X, antinode.Y] = ANTINODE;
 		}
 
 		if (visualise is not null) {
-			string[] output = ["", title, .. copy.PrintAsStringArray(0)];
+			string[] output = ["", title, .. vMap.AsStrings()];
 			_ = Task.Run(() => visualise?.Invoke(output, false));
 		}
 	}
-
-	private const char ANTINODE = '#';
 }