/*
* IntersectionStrategy takes it this far:
9 8
3 2 7 1 9 8
5 4 8 2
7 4 6 9
2 9
1 3 7
>4< 5 2
5 6 1 4 8 7 3
5 4
* Take it further! (resolve that >4<)
*/
public Cell Solve(Board board)
{
// iterate over all numbers
foreach (var cellValue in Cell.All)
{
// for each sub-grid
for (var x = 0; x < Board.GridSize; x++)
{
for (var y = 0; y < Board.GridSize; y++)
{
// and search
var values = board.GetGridCells (x,y);
if (values.Contains(cellValue))
{
continue;
}
// attempt solve this
var availablePositions = board
.GetGridCells(x, y)
.Where(i => !i.IsAssigned())
.ToArray();
// check columns
var adjacentColumnPositions = GetColumnPositions (board, cellValue, x);
var adjacentRowPositions = GetRowPositions (board, cellValue, y);
var candidates =
availablePositions
.ExcludeOn(adjacentColumnPositions, i => i.X)
.ExcludeOn(adjacentRowPositions, i => i.Y)
.ToArray();
if (candidates.Length == 1)
{
var target = candidates[0];
var move = target.Apply(cellValue);
Statistics.NeighbouringNumbersStrategyMoves++;
return move;
}
}
}
}
// give up
return null;
}
public static Cell[] GetValueCandidates(Board board, Cell cell)
{
var columnValues = board.GetAssignedColumnCells(cell);
var rowValues = board.GetAssignedRowCells(cell);
var gridValues = board.GetGridCells(cell)
.Where(i => i.IsAssigned())
.ToArray();
var all = Cell.All;
// BUG: "all" keeps bad positional value, corrupting board.
var missingColumnValues = all.Except(columnValues).ToArray();
var missingRowValues = all.Except(rowValues) .ToArray();
var missingGridValues = all.Except(gridValues) .ToArray();
var candidates = missingColumnValues
.Intersect(missingRowValues)
.Intersect(missingGridValues)
.ToArray();
return candidates;
}
