private SudokuGrid iteratePartialSolution(int row, int column, SudokuGrid sudokuGrid) {
if (row >= 9) {
return sudokuGrid;
}
iterationCounter++;
int newColumn = (column + 1) % 9;
int newRow = row + (newColumn == 0 ? 1 : 0);
if (sudokuGrid.getFieldValue(row, column) == 0) {
for (byte value = 1; value <= 9; value++) {
// printDebugInfo(row, column, value);
SudokuGrid newSudokuGrid = sudokuGrid.setFieldValue(row, column, value);
if (validateSudokuForField(row, column, newSudokuGrid)) {
SudokuGrid resultSudokuGrid = iteratePartialSolution(newRow, newColumn, newSudokuGrid);
if (resultSudokuGrid != null) {
return resultSudokuGrid;
}
}
sudokuGrid.resetFieldValue(row, column);
}
} else {
return iteratePartialSolution(newRow, newColumn, sudokuGrid);
}
return null;
}
private boolean validateRowConstraint(int row, SudokuGrid sudokuGrid) {
int[] distinctValueChecker = new int[10];
for (int column = 0; column < 9; column++) {
if (sudokuGrid.getFieldValue(row, column) > 0
&& (++distinctValueChecker[sudokuGrid.getFieldValue(row, column)]) > 1) {
return false;
}
}
return true;
}
@Override
public byte[][] solve(byte[][] sudoku) {
SudokuGrid sudokuGrid = new SudokuModifieableGrid(sudoku);
sudokuGrid = iteratePartialSolution(0, 0, sudokuGrid);
System.out.println("Number of iterations = " + iterationCounter);
if (sudokuGrid != null) {
return sudokuGrid.getCanonicalRepresentation();
} else {
return null;
}
}
private boolean validateBlockConstraint(int row, int column, SudokuGrid sudokuGrid) {
int[] distinctValueChecker = new int[10];
int blockRowStart = (row / 3) * 3;
int blockColumnStart = (column / 3) * 3;
for (int blockRow = blockRowStart; blockRow < blockRowStart + 3; blockRow++) {
for (int blockColumn = blockColumnStart; blockColumn < blockColumnStart + 3; blockColumn++) {
if (sudokuGrid.getFieldValue(blockRow, blockColumn) > 0
&& (++distinctValueChecker[sudokuGrid.getFieldValue(blockRow, blockColumn)]) > 1) {
return false;
}
}
}
return true;
}