/**
 * Framework for a Sudoku grid.
 *   @author Dave Reed
 *   @version 11/27/10
 */
public class SudokuGrid {
    private char[][] grid;

    /**
     * Constructs an empty 9x9 Sudoku Grid.
     */
    public SudokuGrid() {
        this(9);
    }

    /**
     * Constructs an empty, square Sudoku grid.
     * @param boardSize the length of each row & column
     */
    public SudokuGrid(int gridSize) {
        this.grid = new char[gridSize][gridSize];
        for (int r = 0; r < this.grid.length; r++) {
            for (int c = 0; c < this.grid.length; c++) {
                this.grid[r][c] = '-';
            }
        }
    }

    /**
     * Constructs a partially filled Sudoku grid.
     * @param str the contents of the grid (using '-' for blank)
     */
    public SudokuGrid(String str) {
        String[] contents = str.split("\\s+");
        int gridSize = (int)Math.sqrt(contents.length);

        this.grid = new char[gridSize][gridSize];
        for (int i = 0; i < contents.length; i++) {
            this.grid[i/gridSize][i%gridSize] = contents[i].charAt(0);
        }
    }

    /**
     * Fills the Sudoku grid with numbers using recursive backtracking.
     * @return whether the grid was successfully filled
     */
    public boolean fillGrid() {
       return false;
    }

    /**
     * Constructs a String representation of the grid.
     * @return the grid in a displayable row/column format
     */
    public String toString() {
        String output = "";
        for (int r = 0; r < this.grid.length; r++) {
            for (int c = 0; c < this.grid.length; c++) {
                output += grid[r][c] + " ";
            }
            if (r < this.grid.length-1) {
                output += "\n";
            }
        }
        return output;
    }
}