public Observatory Star1(Day10Input input)
{
var observatories = new List <Observatory>();
for (var i = 0; i < input.Space.Rows; i++)
{
for (var j = 0; j < input.Space.Columns; j++)
{
var inputClone = (Day10Input)input.Clone();
var space = inputClone.Space;
var me = space[i, j];
if (!me.ContainsAsteroid)
{
continue;
}
var currentRange = 1;
while (true)
{
var region = space.GetRectFillInvalid(Region.FromCenter(i, j, currentRange, currentRange));
for (var i1 = 0; i1 < region.Rows; i1++)
{
for (var j1 = 0; j1 < region.Columns; j1++)
{
var objective = region[i1, j1];
if (objective.Position == new Point(-1, -1))
{
continue;
}
if (objective.Position.Y == i && objective.Position.X == j)
{
continue; // self
}
if (!objective.ContainsAsteroid)
{
continue;
}
var vector = new Point(objective.Position.X - me.Position.X, objective.Position.Y - me.Position.Y);
var lcm = LCM(vector.X, vector.Y);
if (lcm is {} lcmV)
{
vector = new Point(vector.X / lcmV, vector.Y / lcmV);
}
if (vector.X == 0)
{
vector.Y = vector.Y < 0 ? -1 : 1;
}
if (vector.Y == 0)
{
vector.X = vector.X < 0 ? -1 : 1;
}
var relPoint = objective.Position;
while (true)
{
relPoint = new Point(relPoint.X + vector.X, relPoint.Y + vector.Y);
if (relPoint.X < 0 || relPoint.X >= input.Space.Columns ||
relPoint.Y < 0 || relPoint.Y >= input.Space.Rows)
{
break;
}
space[relPoint.Y, relPoint.X].Shadowed = true;
}
}
}
currentRange += 2;
if (currentRange / 2 > input.Space.Rows && currentRange / 2 > input.Space.Columns)
{
break;
}
}
var observatory = new Observatory
{
Space = space,
Location = new Point(j, i),
TotalVisibleAsteroids = space.GetFlat().Count(c => c.IsVisible) - 1
};
observatories.Add(observatory);
}
}
return(observatories.OrderByDescending(c => c.TotalVisibleAsteroids).First());
}
public static Matrix <SpaceUnit> GetRectFillInvalid(this Matrix <SpaceUnit> mat, Region region)
{
var t = new Matrix <SpaceUnit>(region.Height, region.Width);
var r = 0;
var c = 0;
for (var i = region.Top; i < region.Bottom; i++, r++, c = 0)
{
for (var j = region.Left; j < region.Right; j++, c++)
{
if (i >= 0 && i < mat.Columns &&
j >= 0 && j < mat.Rows)
{
t[r, c] = mat[i, j];
}
else
{
t[r, c] = new SpaceUnit
{
Position = new Point(-1, -1)
}
}
}
}
;
return(t);
}