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)); } }