The_Eight_Queens_in_java.zip_The Eight

import java.awt.* ; import java.awt.event.* ; import java.applet.* ; public class The_Eight_Queens extends Applet implements ActionListener { List solutionList ; String msg="SOLUTIONS TO THE EIGHT QUEENS PROBLEM "; String msg2="Click on a number in the List Box."; String msg3="Then click 'View' to see the corresponding positions of Queens on the ChessBoard."; String msg4="Or simply Double Click on a number to see the corresponding positions of Queens."; String msg5="The Corresponding Positions of Queens are indicated by RED squares on the Board ."; Label lbl1=new Label(msg); Label lbl2=new Label(msg2); Label lbl3=new Label(msg3); Label lbl4=new Label(msg4); Label lbl5=new Label(msg5); Button b1=new Button("View"); int equiv[]=new int[8]; int solution[] = new int[8] ; int currentRow ; int flag=1; public void init() { setLayout(new FlowLayout(FlowLayout.LEFT)); currentRow = 0 ; solutionList=new List(8,false) ; setBackground(Color.black); setForeground(Color.orange); add(lbl1); add(lbl2); add(lbl3); add(lbl4); msg=""; add(solutionList); add(b1); solutionList.addActionListener(this); b1.addActionListener(this); add(lbl5); } public void actionPerformed(ActionEvent e) { String msg2=solutionList.getSelectedItem(); int equivalent=Integer.parseInt(msg2); for(int ctrn=0;ctrn<=7;ctrn++) { equiv[ctrn]=equivalent%10 ; equivalent=equivalent/10; }; repaint(); } public void paint(Graphics g) { int ctr1,ctr2,row,col ; for(ctr1=0;ctr1<=63;ctr1++) { row=(int)(ctr1%8); col =(int)(ctr1 / 8 ); if((row+col)%2==0) { g.setColor(Color.gray); g.fillRect(310+10*row,118+10*col,10,10); } else if ((row+col)%2==1) { g.setColor(Color.white); g.fillRect(310+10*row,118+10*col,10,10); }; } if(equiv[0]!=0) for(ctr1=0;ctr1<=7;ctr1++) { row=ctr1; col = equiv[7-ctr1]-1; g.setColor(Color.red); g.fillRect(310+10*row,118+10*col,10,10); }; } public void start() { for(int ctr1=0;ctr1<=7;ctr1++) placeQueens(0,ctr1); } public void placeQueens(int row,int col) { solution[row]=col ; int ctr1,ctr2; if(row==7) { displayQueens() ; return ; }; int flagX = 1 ; for(ctr2=0;ctr2<=7;ctr2++) { flagX=1 ; for(ctr1=0;ctr1<=row;ctr1++) if(solution[ctr1] == ctr2 || (solution[ctr1]-ctr2)*(solution[ctr1]-ctr2)== (row+1-ctr1)*(row+1-ctr1) ) flagX=0; if(flagX==1) placeQueens(row+1,ctr2); }; } public void displayQueens() { msg=""; int ctr1; for(ctr1=0;ctr1<=7;ctr1++) msg+=(solution[ctr1]+1); solutionList.add(msg); } }