private bool FillGrid(int[,] grid)
{
for (int i = 0; i < grid.Length; i++)
{
int row = (int)Math.Floor(i / 9.0);
int col = i % 9;
if (grid[row, col] == 0)
{
var numList = GetRandomNumberList();
foreach (var val in numList)
{
if (_validator.ValidPositionForValue(val, row, col, grid))
{
grid[row, col] = val;
if (_validator.GridIsComplete(grid))
{
return(true);
}
else
{
if (FillGrid(grid))
{
return(true);
}
}
}
}
// could not find a valid number
// back-propagate, return and make a new try with the previous cell
grid[row, col] = 0;
return(false);
}
}
return(false);
}
private bool _SolveGrid(int[,] grid)
{
for (int i = 0; i < grid.Length; i++)
{
int row = (int)Math.Floor(i / 9.0);
int col = i % 9;
if (grid[row, col] == 0)
{
foreach (var val in numberList)
{
if (_validator.ValidPositionForValue(val, row, col, grid))
{
grid[row, col] = val;
if (_validator.GridIsComplete(grid))
{
// detect one found solution
NumSolutions++;
if (NumSolutions > 1)
{
return(true);
}
}
else
{
if (_SolveGrid(grid))
{
return(true);
}
}
}
}
// Could not find a valid value, back-propagate one step
grid[row, col] = 0;
break;
}
}
return(false);
}