/* Takes a partially filled-in grid and attempts to assign values to
all unassigned locations in such a way to meet the requirements
for Sudoku solution (non-duplication across rows, columns, and boxes) */
bool SolveSudoku(int grid[N][N])
{
int row, col;
// If there is no unassigned location, we are done
if (!FindUnassignedLocation(grid, row, col))
return true; // success!
// consider digits 1 to 9
for (int num = 1; num <= 9; num++)
{
// if looks promising
if (isSafe(grid, row, col, num))
{
// make tentative assignment
grid[row][col] = num;
// return, if success, yay!
if (SolveSudoku(grid))
return true;
// failure, unmake & try again
grid[row][col] = UNASSIGNED;
}
}
return false; // this triggers backtracking
}
bool SolveSudoku(int grid[][N])
{
int row, col;
if (!FindUnassignedLocation(grid, row, col))
{
return true; // solved it
}
for (int num = 1; num <= 9; ++num)
{
if (IsSafe(grid, row, col, num))
{
grid[row][col] = num;
if (SolveSudoku(grid))
{
return true;
}
else
{
grid[row][col] = 0;
}
}
}
return false;
}
bool SolveSudoku(int grid[N][N])
{
int row, col;
if (!FindUnassignedLocation(grid, row, col))
return true;
for (int num = 1; num <= 9; num++)
{
if (isSafe(grid, row, col, num))
{
grid[row][col] = num;
if (SolveSudoku(grid))
return true;
grid[row][col] = UNASSIGNED;
}
}
return false;
}
int SolveSudoku(int grid[N][N])
{
int row, col;
if (!FindUnassignedLocation(grid, &row, &col))
return true;
long num[N] = {0,0,0,0,0,0,0,0,0};
setCandidates(&num);
for (int i = 0; i <= 8; i++)
{
if (isSafe(grid, row, col, num[i]))
{
grid[row][col] = num[i];
if (SolveSudoku(grid))
return true;
grid[row][col] = UNASSIGNED;
}
}
return false;
}
int solveSudoku(int sudoku[MAX_BOUNDS][MAX_BOUNDS]){
int row, col,num;
if (!FindUnassignedLocation(sudoku,&row,&col))
return 1;
for ( num = 1; num <= 9; num++)
{
// if looks promising
if (isSafe(sudoku, row, col, num))
{
// make tentative assignment
sudoku[row][col] = num;
// return, if success, yay!
if (solveSudoku(sudoku))
return 1;
// failure, unmake & try again
sudoku[row][col] = UNASSIGNED;
}
}
return 0; // this triggers backtracking
}
