// NQueenClient
//
//
import java.awt.Graphics;

class NQueen {
	protected int n;
	protected int board[];
	protected boolean rows[], up[], down[];
	protected NQueenApplet ap;

	NQueen(NQueenApplet ap) {
		this.ap = ap;
		n = ap.getN();
		rows = new boolean[n];
		board = new int[n];
		up   = new boolean[2 * n - 1];
		down = new boolean[2 * n - 1];
		for (int i = 0; i < n; i++) {
			board[i] = 0;
			rows[i] = true;
		}
		for (int i = 2 * n - 2; i >= 0; i--) {
			up[i] = true;
			down[i] = true;
		}
	}

	public int[] getBoard() {
		return board;
	}

	public void try_it(int col) {
		for (int row = 0; row < n; row++) {
			if (rows[row] && up[col + row] && down[col - row + n - 1]) {
				board[col] = row;
				rows[row] = false; up[col + row] = false; down[col - row + n - 1] = false;
				if (col + 1 == n)
					ap.printIt();
				else
					try_it(col + 1);
				rows[row] = true; up[col + row] = true; down[col - row + n - 1] = true;
			}				
		}
	}
}

public class NQueenApplet extends java.applet.Applet implements Runnable
{
	NQueen nq;
	Thread runner;
	int buffer[];
	int c = 0;
	int n = 0;

	public int getN() {
		return n;	
	}

	public void init() {
		n = 8;
		resize(300, 300);
	}

	public void start() {
		if (runner == null) {
			runner = new Thread(this);
			runner.start();
		}
	}

	public void stop() {
		if (runner != null) {
			runner.stop();
			runner = null;
		}
	}

	public void paint(Graphics g) {
		int x0 = 10;
		int y0 = 40;
		int dx = 20;
		int dy = 20;

		if (buffer == null)
			return;
		g.drawString("Count: " + c, x0, y0 - 15);
		for (int i = 0; i <= n; i++) {
			g.drawLine(x0, y0 + dy * i, x0 + dx * n, y0 + dy * i);
			g.drawLine(x0 + dx * i, y0, x0 + dx * i, y0 + dy * n);
		}
		for (int i = 0; i < n; i++) {
			g.drawString("Q", x0 + dx * i + 5, y0 + dy * (buffer[i] + 1) - 5);
		}
	}
	public void printIt() {
		buffer = nq.getBoard();
		c++;
		repaint();
		try {
			Thread.sleep(200);
		} 
		catch (InterruptedException ie) {}
	}
	public void run() {
		c = 0;
		showStatus("ｎクイーン開始");
		nq = new NQueen(this);
		nq.try_it(0);
	}
}