The solution of hanoi problem given by this program is always optimal. You can enter the number of disks first. This lets you solve puzzle of any level of difficulty. The program is as follows.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class HanoiAnimated extends JPanel{
static int tower[][];// the three towers' disks as stack
static int top[];//top of the three stacks
static int from,to;//moving 'from' tower number 'to' tower number
static int diskInAir;//number of disk moved (1 to n)
static int n,l,b,u;
static Color colors[]={Color.BLUE,Color.CYAN,Color.GREEN,Color.MAGENTA,Color.ORANGE,Color.PINK,Color.RED,Color.YELLOW};
public HanoiAnimated()
{
tower=new int[3][10];
top=new int[3];
}
static void push(int to, int diskno)
//putting disk on tower
{
tower[to-1][++top[to-1]]=diskno;
}
static int pop(int from)
//take topmost disk from tower
{
return(tower[from-1][top[from-1]--]);
}
Color getColor(int disknum)
{
return colors[disknum%8];
}
void drawStill(Graphics g)
{
int j,i,disk;
g.clearRect(0,0,getWidth(),getHeight());
for(j=1;j<=3;j++)
{
//draw tower
g.setColor(Color.GRAY);
g.fillRoundRect(j*l,u,5,b-u,1,1);
//draw all disks on tower
for(i=0;i<=top[j-1];i++)
{
disk=tower[j-1][i];
g.setColor(getColor(disk));
g.fillRect(j*l-15-disk*5,b-(i+1)*10,35+disk*10,10);
}
}
}
void drawFrame(Graphics g,int x,int y)
{
try{
drawStill(g);
g.setColor(getColor(diskInAir));
g.fillRect(x-15-diskInAir*5,y-10,35+diskInAir*10,10);
Thread.sleep(60);
}catch(InterruptedException ex){}
}
void animator(Graphics g)
//to show the movement of disk
{
int x,y,dif,sign;
diskInAir=pop(from);
x=from*l;
y=b-(top[from-1]+1)*10;
//taking disk upward from the tower
for(;y>u-20;y-=8)
drawFrame(g, x, y);
y=u-20;
dif=to*l-x;
sign=dif/Math.abs(dif);
//moving disk towards a target tower
for(;Math.abs(x-to*l)>=24;x+=sign*12)
drawFrame(g, x, y);
x=to*l;
//placing disk on a target tower
for(;y<b-(top[to-1]+1)*10;y+=8)
drawFrame(g, x, y);
push(to,diskInAir);
drawStill(g);
}
void moveTopN(Graphics g, int n, int a, int b, int c) throws InterruptedException
//Move top n disk from tower 'a' to tower 'c'
//tower 'b' used for swapping
{
if(n>=1)
{
moveTopN(g,n-1,a,c,b);
drawStill(g);
Thread.sleep(700);
from=a;
to=c;
//animating the move
animator(g);
moveTopN(g,n-1,b,a,c);
}
}
public static void main(String[] args)
{
int i;
String s=JOptionPane.showInputDialog("Enter number of disks");
n=Integer.parseInt(s);
HanoiAnimated ha=new HanoiAnimated();
//setting all tower empty
for(i=0;i<3;i++)
top[i]=-1;
//putting all disks on tower 'a'
for(i=n;i>0;i--)
{
push(1,i);
}
JFrame fr=new JFrame();
fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
fr.setLayout(new BorderLayout());
fr.setSize(640,360);
fr.add(ha);
ha.setSize(fr.getSize());
fr.setVisible(true);
l=ha.getWidth()/4;
b=ha.getHeight()-50;
u=b-n*12;
//start solving
try{
ha.moveTopN(ha.getGraphics(),n,1,2,3);
}catch(Exception ex){}
}
}
