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#include "sudoku.h"
Sudoku::Sudoku()
{
}
Sudoku::Sudoku(const Sudoku & other)
{
assign(other);
}
void Sudoku::assign(const Sudoku & other)
{
for (int row = 0; row < 9; row++) {
for (int column = 0; column < 9; column++) {
sudoku_cell[row][column].assign(other.sudoku_cell[row][column]);
}
}
}
int Sudoku::compare_and_assign(const Sudoku & other)
{
int d = 0;
for (int row = 0; row < 9; row++) {
for (int column = 0; column < 9; column++) {
if (sudoku_cell[row][column].value() != other.sudoku_cell[row][column].value()) {
d++;
}
sudoku_cell[row][column].assign(other.sudoku_cell[row][column]);
}
}
return d;
}
void Sudoku::set_value(int row, int column, int cell_value)
{
sudoku_cell[row][column].set_value(cell_value);
}
void Sudoku::validate()
{
for (int row = 0; row < 9; row++) {
for (int column = 0; column < 9; column++) {
validate_cell(row, column);
}
}
}
// validate_cell calculates the possible values for a cell
void Sudoku::validate_cell(int pos_row, int pos_column)
{
// reset all possibilities for this cell
for (int possible_value = 0; possible_value < 9; possible_value++) {
sudoku_cell[pos_row][pos_column].set_possibility(possible_value, true);
}
// eliminate row
for (int column = 0; column < 9; column++) {
if (column != pos_column) {
const int v = value(pos_row,column);
if ((v > 0) && (v <= 9)) {
sudoku_cell[pos_row][pos_column].set_possibility(v -1, false);
}
}
}
// eliminate column
for (int row = 0; row < 9; row++) {
if (row != pos_row) {
const int v = value(row,pos_column);
if ((v > 0) && (v <= 9)) {
sudoku_cell[pos_row][pos_column].set_possibility(v -1, false);
}
}
}
// eliminate subgrid
int grid_row = pos_row - (pos_row % 3);
int grid_column = pos_column - (pos_column % 3);
for (int row = grid_row; row < grid_row + 3; row++) {
for (int column = grid_column; column < grid_column + 3; column ++) {
if ((column != pos_column) && (row != pos_row)) {
const int v = value(row, column);
if ((v > 0) && (v <= 9)) {
sudoku_cell[pos_row][pos_column].set_possibility(v -1, false);
}
}
}
}
}
/*
* The coverage solver verifies the constraint which imposes that each
* value from 1-9 has to appear exactly once in each row, column and subgrid
* Cells with a unique solution are solved
*/
int Sudoku::solve_coverage()
{
// calculate cell.possibilities
validate();
Sudoku solution(*this);
// for each possible value
for (int v = 1; v <= 9; v++) {
// verify coverage for each row
for (int row = 0; row < 9; row++) {
int available_column = 0;
int covered = 0;
// verify if there's exactly one possibility for v in this row
for (int column = 0; column < 9 ; column++) {
if (!value(row, column) && sudoku_cell[row][column].possibility(v - 1)) {
// value is still possible for this cell
available_column = column;
} else {
covered++;
}
}
if (covered == 8) {
// value is only possible for a single cell
solution.set_value(row, available_column, v);
}
}
// verify coverage for each column
for (int column = 0; column < 9; column++) {
int available_row = 0;
int covered = 0;
// verify if there's exactly one possibility for v in this column
for (int row = 0; row < 9; row++) {
if (!value(row, column) && sudoku_cell[row][column].possibility(v - 1)) {
// value is still possible a single cell
available_row = row;
} else {
covered++;
}
}
if (covered == 8) {
// value is only possible for a single cell
solution.set_value(available_row, column, v);
}
}
// verify coverage for each subgrid
for (int subgrid = 0; subgrid < 9; subgrid++) {
// TODO the subgrid and subgrididx indices need te be delinearized
// and translated into cell coordinates
// verify if there's exactly one possibility for v in this subgrid
for (int subgrididx = 0; subgrididx < 9; subgrididx++) {
}
}
}
return compare_and_assign(solution);
}
/*
* The constraint solver verifies the constraint that each value from 1-9
* can appear only once in each column, row and subgrid
* Cells with a unique solution are solved
*/
int Sudoku::solve_constraints()
{
Sudoku solution;
for (int row = 0; row < 9; row++) {
for (int column = 0; column < 9; column++) {
solution.set_value(row, column, solve_constraints(row, column));
}
}
return compare_and_assign(solution);
}
int Sudoku::solve_constraints(int pos_row, int pos_column)
{
// verify if the cell has already been solved
if ((value(pos_row,pos_column) > 0 ) && (value(pos_row,pos_column) <= 9)) {
return value(pos_row,pos_column);
}
bool possible_solution[9];
for (int idx = 0; idx < 9; idx++) {
possible_solution[idx] = true;
}
// eliminate row
for (int column = 0; column < 9; column++) {
if (column != pos_column) {
const int v = value(pos_row,column);
if ((v > 0) && (v <= 9)) {
possible_solution[v - 1] = false;
}
}
}
// eliminate column
for (int row = 0; row < 9; row++) {
if (row != pos_row) {
const int v = value(row,pos_column);
if ((v > 0) && (v <= 9)) {
possible_solution[v - 1] = false;
}
}
}
// eliminate subgrid
int grid_row = pos_row - (pos_row % 3);
int grid_column = pos_column - (pos_column % 3);
for (int row = grid_row; row < grid_row + 3; row++) {
for (int column = grid_column; column < grid_column + 3; column ++) {
if ((column != pos_column) && (row != pos_row)) {
const int v = value(row, column);
if ((v > 0) && (v <= 9)) {
possible_solution[v - 1] = false;
}
}
}
}
int nbeliminated = 0;
int solution = 0;
for (int idx = 0; idx < 9; idx++) {
if (!possible_solution[idx]) {
nbeliminated++;
} else {
solution = idx + 1;
}
}
if (nbeliminated == 8) {
return solution;
} else {
return 0;
}
}
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