/* 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]) { int row, col; // If there is no unassigned location, we are done if (!FindUnassignedLocation(grid, row, col)) return true; // success! // consider digits 1 to 16 for (int num = 1; num <= n; num++) { // if looks promising if (isSafe(grid, row, col, num)) { // make tentative assignment grid[(row)+(col*n)] = num; // return, if success, yay! if (SolveSudoku(grid)) return true; // failure, unmake & try again grid[(row)+(col*n)] = UNASSIGNED; } } return false; // this triggers backtracking }