// Assumes the station starts rotating clockwise from vertical
public SolarObject GetNthAsteroidVaporized(
SolarGridPoint centerPoint,
int n)
{
if (n < 1)
{
throw new ArgumentOutOfRangeException(nameof(n));
}
// Initialize the set of objects remaining
var pointsRemaining = _solarObjectDictionary
.Select(kvp => kvp.Key)
.ToHashSet();
if (pointsRemaining.Contains(centerPoint))
{
pointsRemaining.Remove(centerPoint);
}
// Initialize the ordered list of objects vaporized
var objectsVaporized = new List <SolarObject>();
// On each rotation, get the list of objects vaporized, ordered
// clockwise from the starting angle
int currentRotation = 1;
var startingLaserVector = new Tuple <Radical, Radical>(0, -1);
while (pointsRemaining.Count > 0)
{
// Get the list of objects seen (and therefore vaporized)
// on this rotation
var objectsVaporizedOnRotation =
GetObjectsVisibleFromPoint(centerPoint, pointsRemaining);
// Order by clockwise angle
var objectsVaporizedOnRotationOrdered = objectsVaporizedOnRotation
.Select(o => new Tuple <double, SolarObject>(
VectorHelper.GetClockwiseAngleBetweenVectors(
startingLaserVector,
SolarGridPoint.GetDifferenceVector(centerPoint, o.GridPoint).ToRadicalVector()),
o))
.OrderBy(o => o.Item1)
.ToList();
// Remove the objects vaporized from the remaining list
foreach (var vaporizedObject in objectsVaporizedOnRotation)
{
if (pointsRemaining.Contains(vaporizedObject.GridPoint))
{
pointsRemaining.Remove(vaporizedObject.GridPoint);
}
}
// Add ordered list of objects to
objectsVaporized.AddRange(objectsVaporizedOnRotationOrdered.Select(o => o.Item2));
currentRotation++;
}
// Get the nth item
if (n - 1 >= objectsVaporized.Count)
{
return(null);
}
return(objectsVaporized[n - 1]);
}
public IList <SolarObject> GetObjectsVisibleFromPoint(
SolarGridPoint point,
HashSet <SolarGridPoint> pointsToCheck)
{
// Define a "jump vector" as a displacement from the given
// central point to another point.
// 1) For each integer n starting with 1, find all jump vectors where
// |x| + |y| = n.
// 2a) For each jump vector for a given n, move outwards from the
// central point in multiples of the given jump vector.
// 2b) If a point is encountered containing an object that hasn't
// been seen before, then mark that object as seen. Afterwards,
// mark any subsequent objects encountered as blocked.
IList <SolarObject> objectsSeen = new List <SolarObject>();
var pointsChecked = new HashSet <SolarGridPoint>();
var displacementVectorsChecked = new HashSet <Tuple <int, int> >();
var numberToCheck = pointsToCheck.Count;
int jumpNumber = 1;
while (pointsChecked.Count < numberToCheck)
{
// Get all jump vectors for this n
var jumpVectors = VectorHelper.GetJumpVectors(jumpNumber);
foreach (var jumpVector in jumpVectors)
{
int jumpStep = 1;
var displacementVector = VectorHelper.MultiplyVector(jumpVector, jumpStep);
if (displacementVectorsChecked.Contains(displacementVector))
{
continue;
}
displacementVectorsChecked.Add(displacementVector);
var currentPoint = SolarGridPoint.GetPointAtRayVector(point, displacementVector);
bool encounteredObjectAlongRay = false;
while (GetIsCoordinateInGrid(currentPoint))
{
if (pointsChecked.Contains(currentPoint))
{
continue;
}
// Check if the point contains an object
if (pointsToCheck.Contains(currentPoint))
{
if (!encounteredObjectAlongRay)
{
objectsSeen.Add(_solarObjectDictionary[currentPoint]);
encounteredObjectAlongRay = true;
}
pointsChecked.Add(currentPoint);
}
jumpStep++;
displacementVector = VectorHelper.MultiplyVector(jumpVector, jumpStep);
displacementVectorsChecked.Add(displacementVector);
currentPoint = SolarGridPoint.GetPointAtRayVector(point, displacementVector);
}
}
jumpNumber++;
}
return(objectsSeen);
}