private Point GetLookAheadLocation(Point currentLocation, Direction direction)
{
return(direction.Id switch
{
'U' => PointUtilities.MoveUp(currentLocation),
'R' => PointUtilities.MoveRight(currentLocation),
'D' => PointUtilities.MoveDown(currentLocation),
'L' => PointUtilities.MoveLeft(currentLocation),
_ => throw new ArgumentOutOfRangeException(nameof(direction), direction, "Unexpected direction")
});
private IReadOnlyList <string> GetRoute(IReadOnlyDictionary <Point, char> view)
{
const char scaffold = '#';
var route = new List <string>();
var currentDirection = Direction.Up;
var currentLocation = view.Single(pixel => pixel.Value == '^').Key;
var keepGoing = true;
var length = 0;
while (keepGoing)
{
var lookAheadLocation = GetLookAheadLocation(currentLocation, currentDirection);
view.TryGetValue(lookAheadLocation, out var lookAheadPixel);
if (lookAheadPixel == scaffold)
{
// Keep going in same direction
length++;
currentLocation = currentDirection.Id switch
{
'U' => PointUtilities.MoveUp(currentLocation),
'R' => PointUtilities.MoveRight(currentLocation),
'D' => PointUtilities.MoveDown(currentLocation),
'L' => PointUtilities.MoveLeft(currentLocation),
_ => throw new ArgumentOutOfRangeException()
};
}
else
{
lookAheadLocation = GetLookAheadLocation(currentLocation, currentDirection.TurnRight);
view.TryGetValue(lookAheadLocation, out lookAheadPixel);
if (lookAheadPixel == scaffold)
{
// Scaffold on the right
if (length > 0)
{
route.Add(length.ToString());
}
route.Add(Direction.Right.Id.ToString());
currentDirection = currentDirection.TurnRight;
length = 0;
}
else
{
lookAheadLocation = GetLookAheadLocation(currentLocation, currentDirection.TurnLeft);
view.TryGetValue(lookAheadLocation, out lookAheadPixel);
if (lookAheadPixel == scaffold)
{
// Scaffold on the left
if (length > 0)
{
route.Add(length.ToString());
}
route.Add(Direction.Left.Id.ToString());
currentDirection = currentDirection.TurnLeft;
length = 0;
}
else
{
// Scaffold only behind so must have reached the end
if (length > 0)
{
route.Add(length.ToString());
}
keepGoing = false;
}
}
}
}
return(route);
}
