public void Setup()
{
boxes = SudokuGenerator.PerformCrossOperation(rows, columns);
// populate rows in grid (9 row) as rowunit. E.g. [0] = A1,B1..I1, [1] = A2,B2..I2 etc.
var rowUnits = new List <string[]>();
foreach (var c in columns)
{
rowUnits.Add(SudokuGenerator.PerformCrossOperation(rows, c.ToString()));
}
// populate columns of grid (9 column) as colunit. E.g. [0] = A1,A21..A9, [1] = B12,B2..B9 etc.
var colUnits = new List <string[]>();
foreach (var r in rows)
{
colUnits.Add(SudokuGenerator.PerformCrossOperation(r.ToString(), columns));
}
}