day 16 part 1

AdventOfCode/Day16.cs

@@ -0,0 +1,96 @@
+
+namespace AdventOfCode;
+
+public class Day16 : BaseDay
+{
+    private string[] _input;
+
+    public Day16() 
+    {
+        _input = File.ReadAllLines(InputFilePath);
+    }
+
+    public override ValueTask<string> Solve_1()
+    {
+        HashSet<Move> energized = new HashSet<Move>();
+        Stack<Move> toVisit = new Stack<Move>();
+
+        Point start = new Point(0, 0);
+        toVisit.Push(new(start, Direction.Right));
+
+        while (toVisit.Any()) 
+        {
+            Move visited = toVisit.Pop();
+            if (energized.Add(visited))
+            {
+                (Move nextOne, Move nextTwo) = NextMove(visited);
+                if (nextOne?.Point != null)
+                {
+                    toVisit.Push(nextOne);
+                }
+                if (nextTwo?.Point != null)
+                {
+                    toVisit.Push(nextTwo);
+                }
+            }
+        }
+        return new(energized.Select(x => x.Point).Distinct().Count().ToString());
+    }
+
+    public override ValueTask<string> Solve_2()
+    {
+        return new("TBD");
+    }
+
+    private (Move one, Move two) NextMove(Move current)
+    {
+        Direction direction = current.Direction;
+        char value = _input[current.Point.I][current.Point.J];
+
+        switch ((value, direction))
+        {
+            case ('.', Direction.Right):
+            case ('\\', Direction.Down):
+            case ('/', Direction.Up):
+            case ('-', Direction.Right):
+                return (new (current.Point.J < _input[0].Length - 1 ? new Point(current.Point.I, current.Point.J + 1) : null, Direction.Right), null);
+            case ('.', Direction.Left):
+            case ('\\', Direction.Up):
+            case ('/', Direction.Down):
+            case ('-', Direction.Left):
+                return (new (current.Point.J > 0 ? new Point(current.Point.I, current.Point.J - 1) : null, Direction.Left), null);
+            case ('.', Direction.Up):
+            case ('\\', Direction.Left):
+            case ('/', Direction.Right):
+            case ('|', Direction.Up):
+                return (new (current.Point.I > 0 ? new Point(current.Point.I - 1, current.Point.J) : null, Direction.Up), null);
+            case ('.', Direction.Down):
+            case ('\\', Direction.Right):
+            case ('/', Direction.Left):
+            case ('|', Direction.Down):
+                return (new (current.Point.I < _input.Length - 1 ? new Point(current.Point.I + 1, current.Point.J) : null, Direction.Down), null);
+            case ('|', Direction.Left):
+            case ('|', Direction.Right):
+                return (new(current.Point.I > 0 ? new Point(current.Point.I - 1, current.Point.J) : null, Direction.Up),
+                    new(current.Point.I < _input.Length - 1 ? new Point(current.Point.I + 1, current.Point.J) : null, Direction.Down));
+            case ('-', Direction.Up):
+            case ('-', Direction.Down):
+                return (new(current.Point.J > 0 ? new Point(current.Point.I, current.Point.J - 1) : null, Direction.Left),
+                    new(current.Point.J < _input[0].Length - 1 ? new Point(current.Point.I, current.Point.J + 1) : null, Direction.Right));
+            default:
+                throw new NotSupportedException();
+        }
+    }
+
+    private record Point(int I, int J);
+
+    private enum Direction
+    { 
+        Right,
+        Left,
+        Down,
+        Up
+    }
+
+    private record Move(Point Point, Direction Direction);
+}