// 3. Searching for Single Candidates: Square
// "is there a value in any square that is only possible in one location?"
public static void SearchSquareForSingleCandidates(this Grid grid)
{
for (int s = 0; s < grid.GridSize; s++)
{
for (int value = 1; value <= grid.GridSize; value++)
{
// that value already exists in the col
if (Array.Exists(grid.GetSquare(s), element => element == value))
{
continue;
}
Tuple <int, int> result = grid.CheckSquareForValueInOptions(s, value);
if (result.Item1 != -1 && result.Item2 != -1)
{
grid.SolveCell(result.Item1, result.Item2, value);
grid.UpdateNeighbours(result.Item1, result.Item2);
}
}
}
}
public static bool IsValidSolution(this Grid grid)
{
if (grid.CompletedCells < grid.GridSize * grid.GridSize)
{
return(false);
}
for (int i = 0; i < grid.GridSize; i++)
{
bool validRow = new HashSet <int>(grid.GetRow(i)).SetEquals(Enumerable.Range(1, grid.GridSize));
bool validCol = new HashSet <int>(grid.GetColumn(i)).SetEquals(Enumerable.Range(1, grid.GridSize));
bool validSquare = new HashSet <int>(grid.GetSquare(i)).SetEquals(Enumerable.Range(1, grid.GridSize));
if (!(validRow & validCol & validSquare))
{
return(false);
}
}
return(true);
}