/// <summary>
/// Finds errors in the grid. Returns a list of cells such that:
/// - there is another cell with the same value in the row
/// - there is another cell with the same value in the column
/// - there is another cell with the same value in the 3x3 square
/// where the cell resides
/// </summary>
public List<List<int>> FindErrors(Grid grid)
{
List<List<int>> errors = new List<List<int>>();
for (int row = 0; row < 9; row++)
{
for (int col = 0; col < 9; col++)
{
int val = grid.Get(row, col);
// The same cell in the row?
bool valueInRow = grid.GetRow(row).Count((eachCell) => eachCell == val) > 1;
// The same cell in the column?
bool valueInCol = grid.GetColumn(col).Count((eachCell) => eachCell == val) > 1;
// The same cell in the 3x3 square?
bool valueInSquare = grid.GetSquareAbout(row, col).Count((eachCell) => eachCell == val) > 1;
if (val != 0 && (valueInRow || valueInCol || valueInSquare))
{
errors.Add(new List<int>(new int[] { row, col }));
}
}
}
return errors;
}
/// <summary>
/// Get the list of valid moves for the given cell in the given grid.
/// Used by the Hints bar and Consider()
/// </summary>
/// <returns>
/// A list of valid move choices.
/// </returns>
public List<int> GetHintsFor(Grid grid, int row, int col)
{
// believe it or not, Lists are faster than int[]s for some reason
List<int> stuff = grid.GetColumn(col).Concat(grid.GetRow(row)).Concat(grid.GetSquareAbout(row, col)).ToList();
List<int> results = new List<int>();
for (int i = 1; i <= 9; i++)
{
if (!stuff.Contains(i))
{
results.Add(i);
}
}
return results;
}
