Add day 15 puzzles solvers

Add day 15 puzzles solvers

Author: vladsm

src/AdventOfCode2021.Runner/TodayPuzzleTests.cs

@@ -1,4 +1,4 @@
-using AdventOfCode.Year2021.Solvers.Day14;
+using AdventOfCode.Year2021.Solvers;
 
 using Xunit;
 using Xunit.Abstractions;
@@ -18,13 +18,13 @@ public TodayPuzzleTests(ITestOutputHelper output)
 	public async Task Result_should_be_accepted_by_site()
 	{
 		await Runner.
-			Solve<IInputEntry, long>(2021, 14, 1).
-			AssertingResult(Helpers.ParseLine).
+			Solve<byte[], int>(2021, 15, 1).
+			AssertingResult(Parsing.ParseToDigitsArray).
 			Run(_output);
 
 		await Runner.
-			Solve<IInputEntry, long>(2021, 14, 2).
-			AssertingResult(Helpers.ParseLine).
+			Solve<byte[], int>(2021, 15, 2).
+			AssertingResult(Parsing.ParseToDigitsArray).
 			Run(_output);
 	}
 }

src/AdventOfCode2021.Solvers/Days/Day-15/Day15Level1Solver.cs

@@ -0,0 +1,12 @@
+namespace AdventOfCode.Year2021.Solvers.Day15;
+
+public sealed class Day15Level1Solver : Day15SolverBase
+{
+	protected override int DimensionsExtendMultiplier => 1;
+
+	protected override int Cost((int, int) location, byte[][] costs)
+	{
+		(int row, int col) = location;
+		return costs[row][col];
+	}
+}

src/AdventOfCode2021.Solvers/Days/Day-15/Day15Level2Solver.cs

@@ -0,0 +1,17 @@
+namespace AdventOfCode.Year2021.Solvers.Day15;
+
+public sealed class Day15Level2Solver : Day15SolverBase
+{
+	protected override int DimensionsExtendMultiplier => 5;
+
+	protected override int Cost((int, int) location, byte[][] costs)
+	{
+		(int col, int row) = location;
+		int height = costs.Length;
+		int width = costs[0].Length;
+		int baseCost = costs[row % height][col % width];
+		int increment = row / height + col / width;
+		int cost = baseCost + increment;
+		return (cost - 1) % 9 + 1;
+	}
+}

src/AdventOfCode2021.Solvers/Days/Day-15/Day15SolverBase.cs

@@ -0,0 +1,89 @@
+namespace AdventOfCode.Year2021.Solvers.Day15;
+
+public abstract class Day15SolverBase : SolverWithArrayInput<byte[], int>
+{
+	protected override int Solve(byte[][] costs)
+	{
+		return new InnerSolver(costs, Cost, DimensionsExtendMultiplier).Solve();
+	}
+
+	protected abstract int DimensionsExtendMultiplier { get; }
+	protected abstract int Cost((int row, int col) location, byte[][] costs);
+
+
+	private class InnerSolver
+	{
+		private readonly int _dimensionsExtendMultiplier;
+		private readonly Func<(int row, int col), int> _getCost;
+		private readonly int _height;
+		private readonly int _width;
+
+		public InnerSolver(
+			byte[][] costs,
+			Func<(int row, int col), byte[][], int> getCost,
+			int dimensionsExtendMultiplier
+			)
+		{
+			_height = costs.Length;
+			_width = costs[0].Length;
+			_getCost = l => getCost(l, costs);
+			_dimensionsExtendMultiplier = dimensionsExtendMultiplier;
+		}
+
+		public int Solve()
+		{
+			var startLocation = (0, 0);
+			var extension = new HashSet<(int row, int col)> { startLocation };
+			var reached = new Dictionary<(int, int), int> { { startLocation, 0 } };
+
+			while (extension.Any())
+			{
+				extension = Extend(extension, reached);
+			}
+
+			var endLocation = (_height * _dimensionsExtendMultiplier - 1, _width * _dimensionsExtendMultiplier - 1);
+			return reached[endLocation];
+		}
+
+		private HashSet<(int, int)> Extend(
+			HashSet<(int, int)> prevExtension,
+			Dictionary<(int, int), int> reached
+			)
+		{
+			var extension = new HashSet<(int, int)>();
+			foreach (var location in prevExtension)
+			{
+				int locationTotalCost = reached[location];
+				ForAdjacent(location, a => processAdjacent(a, locationTotalCost));
+			}
+			return extension;
+
+			void processAdjacent((int row, int col) adjacent, int locationTotalCost)
+			{
+				int newAdjacentTotalCost = _getCost(adjacent) + locationTotalCost;
+				if (reached.TryGetValue(adjacent, out int adjacentTotalCost))
+				{
+					if (newAdjacentTotalCost >= adjacentTotalCost) return;
+					reached[adjacent] = newAdjacentTotalCost;
+				}
+				else
+				{
+					reached.Add(adjacent, newAdjacentTotalCost);
+				}
+				extension.Add(adjacent);
+			}
+		}
+		
+		private void ForAdjacent((int, int) location, Action<(int, int)> action)
+		{
+			int height = _height * _dimensionsExtendMultiplier;
+			int width = _width * _dimensionsExtendMultiplier;
+
+			(int row, int col) = location;
+			if (row > 0) action((row - 1, col));
+			if (row < height - 1) action((row + 1, col));
+			if (col > 0) action((row, col - 1));
+			if (col < width - 1) action((row, col + 1));
+		}
+	}
+}