package queens_8;

public class board {

    private static int board[][];
    private int numQueens;

    public board() {//default constructor
        numQueens = 0;
        board = new int[8][8];
        for (int i = 0; i < 8; i++) {
            for (int j = 0; j < 8; j++) {
                board[i][j] = 0;
         }
        }
    }

    public int getnumQueens() {
        return numQueens;
    }

    public void start() {

        solve(0);

    }

    public boolean solve(int numQueens) {

        if (numQueens == 8) {
            System.out.println("DONE");
            this.display();
            return true;
        } else {
            for (int i = 0; i < 8; i++) {
                for (int j = 0; j < 8; j++) {
                    if (isvalidMove(i, j) == 0) {
                        this.placeQueen(i, j, 0);
                        numQueens++;
                        if (solve(numQueens)) {
                            return true;
                        } else {
                            this.placeQueen(i, j, 1);
                            numQueens--;
                        }
                    }
                }
            }
        }
        return false;
    }

    public static int isvalidMove(int x, int y) {
        for (int i = 0; i < 8; i++) {
            if (get(x, i) == 1) {

                return -1;
            }
            if (get(i, y) == 1) {
                return -1;
            }
        }

        // check diag
        for (int j = 0; j < 8; j++) {
            if (get(x - j, y - j) == 1) {
                return -1;
            }
            if (get(x - j, y + j) == 1) {
                return -1;
            }
            if (get(x + j, y - j) == 1) {
                return -1;
            }
            if (get(x + j, y + j) == 1) {
                return -1;
            }

        }
        return 0;
    }

    public int placeQueen(int x, int y, int type) {

        if (type == 0) {
            board[x][y] = 1;
            numQueens++;
            return 0;
        } else if (type == 1) {
            board[x][y] = 0;
            return 0;

        }
        System.err.println("Wrong type");
        return -3;
    }

    public static int get(int x, int y) {

        if (x < 0 || y < 0 || x > 7 || y > 7) {
            return -1;
        }

        return board[x][y];
    }

    public void display() {
        for (int i = 0; i < 8; i++) {
            for (int j = 0; j < 8; j++) {
                System.out.print(this.get(i, j) + " ");
            }
            System.out.println("");
        }
    }
}