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#include "sudoku.h"
Sudoku::Sudoku()
{
for (int row = 0; row < 9; row++) {
for (int column = 0; column < 9; column++) {
sudoku_value[row][column] = 0;
}
}
}
int Sudoku::solve_step(int pos_row, int pos_column)
{
// verify if the cell has already been solved
if ((sudoku_value[pos_row][pos_column] > 0 ) && (sudoku_value[pos_row][pos_column] <= 9)) {
return sudoku_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) {
int value = sudoku_value[pos_row][column];
if ((value > 0) && (value <= 9)) {
possible_solution[value - 1] = false;
}
}
}
// eliminate column
for (int row = 0; row < 9; row++) {
if (row != pos_row) {
int value = sudoku_value[row][pos_column];
if ((value > 0) && (value <= 9)) {
possible_solution[value - 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)) {
int value = sudoku_value[row][column];
if ((value > 0) && (value <= 9)) {
possible_solution[value - 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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