/// <summary>
/// Populates a matrix such that each 3x3 grid is valid.
/// </summary>
/// <param name="matrix">partially populated matrix</param>
/// <returns>a fully populated matrix where all 3x3 cells are in a valid state</returns>
public static int[][] RandomMatrix(int[][] matrix)
{
var result = CopyMatrix(matrix);
for (int block = 0; block < 9; ++block)
{
var valuesInBlock = result.GetBlock(block).Where(x => x != 0).ToArray();
// Create a shuffled list missing values for block
var list =
new Queue <int>(
Enumerable.Range(1, 9)
.Except(valuesInBlock)
.OrderBy(x => Guid.NewGuid()));
// walk through each cell in the current block
foreach (var index in SudokuExtensions.GetBlockIndexes(block))
{
//if cell is empty add a value from list
if (result[index[0]][index[1]] == 0)
{
result[index[0]][index[1]] = list.Dequeue();
}
}
}
return(result);
}
public static int[][] NeighborMatrix(int[][] problem, int[][] matrix)
{
var result = CopyMatrix(matrix);
var indexes = SudokuExtensions.GetBlockIndexes(rnd.Next(0, 9));
// determine two cells in the same block that don't contain a fixed value
int[][] swaps = indexes
.Where(coord => problem.ValueForIndex(coord) == 0)
.OrderBy(_ => Guid.NewGuid())
.Take(2)
.ToArray();
// pick two of those cells: (r1, c1) (r2,c2)
int r1 = swaps[0][0],
c1 = swaps[0][1],
r2 = swaps[1][0],
c2 = swaps[1][1];
int tmp = result[r1][c1];
result[r1][c1] = result[r2][c2];
result[r2][c2] = tmp;
return(result);
}
public static int[][] MergeMatrices(int[][] m1, int[][] m2)
{
var result = CopyMatrix(m1);
for (var i = 0; i < 9; ++i)
{
if (rnd.NextDouble() > 0.5)
{
var indexes = SudokuExtensions.GetBlockIndexes(i);
foreach (var index in indexes)
{
result[index[0]][index[1]] = m2[index[0]][index[1]];
}
}
}
return(result);
}