我的八皇后

八皇后问题，都知道吧。循环套递归，比汉诺塔还寒，晕归晕，索性弄出来了，撒花~~~


public class Das_n_Damen_Problem extends ChessMiniJava{
    static int n;
    static boolean flag;
 static boolean[][] Platzierung;
 static boolean[] a;
 static boolean[] b;
 static boolean[] c;
 
 public static void main(String[] args){
  write("Wie viele Damen?");
  n=read();
     flag=false;
  Platzierung=new boolean[n][n];
  a=new boolean[n];
  b=new boolean[2*n];
  c=new boolean[2*n];
  re(0);
 }
 
 public static void re(int i){
  if(flag)
   return;
  for(int iSpalte=0;iSpalte<n;iSpalte++){
   if(a[iSpalte]==false && b[i-iSpalte+n]==false && c[i+iSpalte]==false){
    Platzierung[i][iSpalte]=true;
    a[iSpalte]=true;
    b[i-iSpalte+n]=true;
    c[i+iSpalte]=true;
    if(i==n-1){
     paintField(Platzierung);
     flag=true;
     return;
    }
    else{
     re(i+1);
    }
   Platzierung[i][iSpalte]=false;
   a[iSpalte]=false;
   b[i-iSpalte+n]=false;
   c[i+iSpalte]=false;
   }
  }
 }
}


附上ChessMiniJava源代码：
import java.awt.GridLayout;
import javax.swing.JPanel;
import javax.swing.JFrame;

import java.awt.Color;
import java.awt.Font;
import java.awt.Point;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GradientPaint;
import java.awt.RenderingHints;

public class ChessMiniJava extends MiniJava{
    private static class Field extends JPanel {
        boolean black,queen; Point p;
        public Field(boolean black,boolean queen){
            this.black=black;
            this.queen=queen;
            p = getLocation();
        }
 public void paint(Graphics g) {
  super.paint(g);
  if (black) g.setColor(Color.BLACK);
                else g.setColor(Color.WHITE);
                g.fillRect(p.getLocation().x,p.getLocation().y,getWidth()*2,getHeight());
                g.setColor(Color.RED);

                GradientPaint gradient = new GradientPaint(0, 0, Color.YELLOW, getWidth(), 0, Color.RED);
                ((Graphics2D)g).setPaint(gradient);
                ((Graphics2D)g).setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);
                if (queen) {
                    g.fillOval((int)(getWidth()*.1),(int)(getHeight()*.7),(int)(getWidth()*.8),(int)(getHeight()*.2));
                    int[] x = {(int)(getWidth()*.1), (int)(getWidth()*.9), (int)(getWidth()*.9), (int)(getWidth()*.7), (int)(getWidth()*.5), (int)(getWidth()*.3), (int)(getWidth()*.1)};
                    int[] y = {(int)(getHeight()*.8),(int)(getHeight()*.8),(int)(getHeight()*.2),(int)(getHeight()*.6),(int)(getHeight()*.2),(int)(getHeight()*.6),(int)(getHeight()*.2)};
                    g.fillPolygon(x,y,7);
                }
 }
    }
    public static void paintField(boolean[][] field){
        JFrame myFrame = new JFrame("Spielfeld");
        JPanel pan = new JPanel();
        java.util.Set<Integer> s1 = new java.util.HashSet<Integer>(),s2=new java.util.HashSet<Integer>(),s3 = new java.util.HashSet<Integer>(),s4=new java.util.HashSet<Integer>();
        pan.setLayout(new GridLayout(field.length,field.length));
        for (int x = 0 ; x < field.length; x ++){
            for (int y = 0; y < field[x].length; y++){
                pan.add(new Field((x+y)%2 ==1,field[x][y]));
                if (field[x][y]) { s1.add(x);s2.add(y);s3.add(x+y);s4.add(field.length-1-y+x);};
            }
        }
        boolean sol=(s1.size()==field.length)&&(field.length==s2.size())&&(field.length==s3.size())&&(field.length==s4.size());
        if (System.getProperty("SOL","nowshow").equals("show")){
            if (sol) pan.setBorder(javax.swing.BorderFactory.createLineBorder(Color.GREEN,5));
            else pan.setBorder(javax.swing.BorderFactory.createLineBorder(Color.RED,5));
        }
        myFrame.add(pan);
        myFrame.setSize(400,400);
        myFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        myFrame.setVisible(true);
    }
}