public static string Visualise(this Marble start, Marble current)
{
var visualisation = new StringBuilder();
Marble active = start;
do
{
if (active == current)
{
visualisation.Append("(");
visualisation.Append(active.Number);
visualisation.Append(")");
}
else
{
visualisation.Append(active.Number);
}
visualisation.Append(" ");
active = active.Clockwise;
}while (active != start);
return(visualisation.ToString());
}
public static Marble Clockwise(this Marble marble, int count)
{
Marble current = marble;
for (int i = 0; i < count; i++)
{
current = current.Clockwise;
}
return(current);
}
public static Marble Remove(this Marble marble)
{
Marble prev = marble.CounterClockwise;
Marble next = marble.Clockwise;
prev.Clockwise = next;
next.CounterClockwise = prev;
marble.Clockwise = null;
marble.CounterClockwise = null;
return(marble);
}
public static Marble InsertAfter(this Marble marble, int number)
{
Marble next = marble.Clockwise;
var newMarble = new Marble
{
Number = number,
Clockwise = next,
CounterClockwise = marble,
};
marble.Clockwise = newMarble;
next.CounterClockwise = newMarble;
return(newMarble);
}
public long Solve(int players, int marbles)
{
long[] scores = new long[players];
// Set up Marble 0.
// We're going to solve this using a doubly linked list
var marble0 = new Marble
{
Number = 0,
};
marble0.Clockwise = marble0;
marble0.CounterClockwise = marble0;
Marble currentMarble = marble0;
int currentPlayer = 0;
for (int i = 1; i <= marbles; i++)
{
if (i % 23 == 0)
{
// Current player keeps this marble
scores[currentPlayer] += i;
// Also keeps the marble 7 counter clockwise
Marble marbleToRemove = currentMarble.CounterClockwise(7);
currentMarble = marbleToRemove.Clockwise;
scores[currentPlayer] += marbleToRemove.Number;
marbleToRemove.Remove();
}
else
{
currentMarble = currentMarble.Clockwise(1).InsertAfter(i);
}
currentPlayer = ++currentPlayer % players;
}
return(scores.Max());
}