static SudokuBoard ReadBoard(int[] rawBoard)
{
int n = rawBoard.Length;
if(n != SudokuBoard.ROW * SudokuBoard.COLUM) throw new ArgumentException("raw board is not valid");
var rows = new List<int>();
var cols = new List<int>();
var vals = new List<int>();
for (int i = 0; i < n; i++)
{
if (rawBoard[i] != 0)
{
rows.Add(i / 9);
cols.Add(i % 9);
vals.Add(rawBoard[i]);
}
}
var ret = new SudokuBoard();
ret.Init(rows.ToArray(), cols.ToArray(), vals.ToArray());
return ret;
}