public void Step(Railway railway)
{
var prevPoint = new Point(X, Y);
// Move forward
ForwardVector.AddVectorToPoint(this);
var track = railway.Tracks[X, Y];
var neighbours = track.Neighbours();
// Dont go backwards
neighbours.Remove(prevPoint);
// Pick direction
if (neighbours.Count == 1)
{
ForwardVector = Vector.VectorBetweenPoints(this, neighbours[0]);
}
else if (neighbours.Count == 3)
{
switch (NextDirection)
{
case Direction.LEFT:
ForwardVector.RotateLeft();
NextDirection = Direction.UP;
break;
case Direction.UP:
NextDirection = Direction.RIGHT;
break;
case Direction.RIGHT:
ForwardVector.RotateRight();
NextDirection = Direction.LEFT;
break;
default:
throw new Exception("Abnormal NextDirection");
}
}
else
{
throw new Exception("Abnormal number of neighbours");
}
}
static void Main(string[] args)
{
List <string> lines = new List <string>(File.ReadAllLines(@"input.txt"));
// Pick part 1 or 2
var part = 2;
var width = lines[0].Length;
var height = lines.Count();
var railway = new Railway(width, height);
char[] horizontalChars = new char[] { '-', '>', '<', '+' }; // + could be ambiguous e.g. "+\+", but looks like the input avoids this
char[] verticalChars = new char[] { '|', 'v', '^', '+' };
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
switch (lines[y][x])
{
case '-':
railway.SetTrack(new Track(x, y, Direction.LEFT | Direction.RIGHT));
break;
case '|':
railway.SetTrack(new Track(x, y, Direction.UP | Direction.DOWN));
break;
case '\\':
if (x == width - 1 || y == 0 || (x > 0 && horizontalChars.Contains(lines[y][x - 1])) || (y < height - 1 && verticalChars.Contains(lines[y + 1][x])))
{
railway.SetTrack(new Track(x, y, Direction.LEFT | Direction.DOWN));
}
else if (x == 0 || y == height - 1 || (x < width - 1 && horizontalChars.Contains(lines[y][x + 1])) || (y > 0 && verticalChars.Contains(lines[y - 1][x])))
{
railway.SetTrack(new Track(x, y, Direction.RIGHT | Direction.UP));
}
else
{
throw new Exception("Ambiguous character");
}
break;
case '/':
if (x == width - 1 || y == height - 1 || (x > 0 && horizontalChars.Contains(lines[y][x - 1])) || (y > 0 && verticalChars.Contains(lines[y - 1][x])))
{
railway.SetTrack(new Track(x, y, Direction.LEFT | Direction.UP));
}
else if (x == 0 || y == 0 || (x < width - 1 && horizontalChars.Contains(lines[y][x + 1])) || (y < height - 1 && verticalChars.Contains(lines[y + 1][x])))
{
railway.SetTrack(new Track(x, y, Direction.RIGHT | Direction.DOWN));
}
else
{
throw new Exception("Ambiguous character");
}
break;
case '+':
railway.SetTrack(new Track(x, y, Direction.LEFT | Direction.UP | Direction.DOWN | Direction.RIGHT));
break;
case '^':
railway.SetTrack(new Track(x, y, Direction.UP | Direction.DOWN));
railway.Trains.Add(new Train(x, y, Direction.UP));
break;
case '<':
railway.SetTrack(new Track(x, y, Direction.LEFT | Direction.RIGHT));
railway.Trains.Add(new Train(x, y, Direction.LEFT));
break;
case 'v':
railway.SetTrack(new Track(x, y, Direction.UP | Direction.DOWN));
railway.Trains.Add(new Train(x, y, Direction.DOWN));
break;
case '>':
railway.SetTrack(new Track(x, y, Direction.LEFT | Direction.RIGHT));
railway.Trains.Add(new Train(x, y, Direction.RIGHT));
break;
default:
break;
}
}
}
Train train = null;
if (part == 1)
{
while (railway.CollisionTrains.Count() == 0)
{
railway.Step();
}
train = railway.CollisionTrains.First();
}
else
{
while (railway.Trains.Count > 1)
{
railway.Step();
}
train = railway.Trains.First();
}
Console.WriteLine("Result: {0},{1}", train.X, train.Y);
}
