private static IList <int> FindOpenerMoves(Board board)
{
var dimensions = board.Dimensions;
// The middle of a board is of highest priority.
// account for a multi cell middle, e.g. width = 4, height = 3 => middle is at (1,1) and (2,1)
var middleSpan = new CellSpan(1 - dimensions.Width % 2, 1 - dimensions.Height % 2);
var step = new CellSpan(1, 1);
for (
CellCoordinates topLeft = new CellCoordinates(dimensions.Width / 2, dimensions.Height / 2),
bottomRight = topLeft + middleSpan;
CellCoordinates.IsInside(topLeft, dimensions) &&
CellCoordinates.IsInside(bottomRight, dimensions);
topLeft -= step,
bottomRight += step)
{
var cells = Cells.TakeAnyFreeCellInRect(
board,
CellCoordinates.ToCellAt(topLeft, dimensions),
CellCoordinates.ToCellAt(bottomRight, dimensions));
// If cells are already occupied, take a cell from the rectangle around the current one,
if (cells.Length > 0)
{
return(cells);
}
// repeat until a free cell is found.
}
return(Array.Empty <int>());
}
private static IList <int> CompleteConsecutiveness(
Board board,
IEnumerable <Consecutiveness> incompleteMoves)
{
var cells = board.Cells;
var boardDimensions = board.Dimensions;
var moves = new List <int>();
void collect(CellCoordinates coordinates)
{
if (CellCoordinates.IsInside(coordinates, boardDimensions))
{
var cellAt = CellCoordinates.ToCellAt(coordinates, boardDimensions);
if (cells[cellAt] == CellOwner.None)
{
moves.Add(cellAt);
}
}
}
var prioritized = incompleteMoves
.OrderByDescending(consecutiveness => consecutiveness.CellsAt.Count);
foreach (var consecutiveness in prioritized)
{
// single moves cannot be completed in one turn
if (consecutiveness.CellsAt.Count < 2)
{
continue;
}
var first = CellCoordinates.FromCellAt(consecutiveness.CellsAt.First(), boardDimensions);
var second = CellCoordinates.FromCellAt(consecutiveness.CellsAt.Skip(1).First(), boardDimensions);
var last = CellCoordinates.FromCellAt(consecutiveness.CellsAt.Last(), boardDimensions);
var stepSpan = second - first;
collect(first - stepSpan);
collect(last + stepSpan);
}
return(moves);
}
