eight_queen.java

一个用于演示8皇后的手机程序,功能简单,但是算法经典

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

public class Eight_Queen extends MIDlet
{
  private Display display;
  
  public void startApp()
 {
    display = Display.getDisplay(this);
    Eight_QueenCanvas queenCanvas = new Eight_QueenCanvas();
    queenCanvas.start();
    display.setCurrent(queenCanvas);
  }
  
  public Display getDisplay() 
 {
    return display;  
  }
  
  public void pauseApp()
  {
  }

  public void destroyApp(boolean unconditional) 
   {
   System.gc();
    destroyApp(false);
    notifyDestroyed();
  }  
  
 }
class Eight_QueenCanvas extends GameCanvas implements Runnable 
{
  private boolean isPlay;
  private boolean isPlaying;   
  private int width;        
  private int height;       
  static final int Queen_num = 8;
  static final int Result_Nums = 92;
  int Min_Length;
  int queenLength;
  int NCounts ;

  public Eight_QueenCanvas()
  {
    super(true);
    width = getWidth();
    height = getHeight();
    if (width > height) Min_Length = height;
    else Min_Length = width;
    queenLength = Min_Length / 10;
    NCounts = 0;
  }

  // Automatically start thread for game loop
  public void start() 
 {
    isPlay = true;
    isPlaying = true;
    Thread t = new Thread(this);
    t.start();
  }

  public void stop() { isPlaying = false; }

  /************************************************/
  public void run() 
 {
    Graphics g = getGraphics();
    while (isPlaying == true)
	{
	  Juge_Press();
      if (isPlay == false)
		  continue;
      Draw_Grid(g);
      queen(g);
      isPlay = false;
    }
  }

  // Method to Handle User Inputs
  /****************************************************/
  private void Juge_Press() 
  {
    int keyStates = getKeyStates();
    if ((keyStates & RIGHT_PRESSED) !=0 )
		isPlay = true;
    if ((keyStates & DOWN_PRESSED) !=0)
		isPlay = true;
  }
  /**************************************************/

 void Draw_Grid(Graphics g)//画格子
 {
	int x, y, z, i;
	g.setColor(0, 255, 0);
    g.fillRect(0, 0, getWidth(), getHeight());
	g.setColor(0,0,255);
	for(i = 0; i <= Queen_num; i++)
	{
		g.drawLine(queenLength, queenLength + i*queenLength, Min_Length - queenLength, queenLength + i*queenLength);
		g.drawLine(queenLength + i*queenLength, queenLength, queenLength + i*queenLength, Min_Length - queenLength);
	}
	flushGraphics();
 }
 /********************************************/
 void Draw_Queen(int row, int col, Graphics g)//画皇后
{
	int left, top;
	int i;
	int length;
	length = queenLength / 10;
	left = (col+1) * queenLength;
	top = (row+1) * queenLength;
	g.setColor(255, 0,0);
	g.fillRoundRect(left + length, top + length, queenLength - 2*length, queenLength - 2*length, queenLength , queenLength );
	flushGraphics();
}
/**********************************************************/
void queen(Graphics g)//主程序
{
	g.setColor(255,0,0);
	g.drawString("                                       8 皇 后",0,0,0);
	int i, cur_counts, j, k, m;
	int col, row;
	if (NCounts++ > Result_Nums)
	{
		NCounts = 0;
		return;
	}
		
	int[] arrCol = new int[Queen_num];
	int[] arrRow = new int[Queen_num];
	for (i = 0; i < Queen_num; i++)
	{
		arrCol[i] = -1;
		arrRow[i] = -1;
	}
	cur_counts = 0;
	col = 0;
	row = 0;
	
	while (true)
	{
		for (; col < Queen_num; col++)
		{
			if (arrCol[col] == -1) break;
		}
		if (col == Queen_num)
		{
			row--;
			if (row < 0) break;
			arrCol[arrRow[row]] = -1;
			col = arrRow[row] + 1;
			arrRow[row] = -1;
			continue;
		}
		k = row + 1;
		for (i = 0; i < row; i++)
		{
			j = col - arrRow[i];
			k--;
			if (!(j == k || j == -k)) continue;
			if (((j + k) & 1) == 0) break;
		}
		if (i != row)
		{
			col++;
			continue;
		}
		if (row == Queen_num - 1)
		{
			cur_counts++;
			arrRow[row] = col;
			if (cur_counts >= NCounts)
			{
				for (i = 0; i < Queen_num; i++) 
				{
					try { 
      					Thread.sleep(100); 
      					Draw_Queen(i, arrRow[i], g);
					}
      				catch (InterruptedException ie) {}
      			}
				return;
			}
			arrRow[row] = -1;
			col++;
		}
		else 
		{
			arrCol[col] = row;
			arrRow[row] = col;
			row++;
			col = 0;
		}
	}
  }
}