So I'm trying to animate the common puzzle Tower of Hanoi. I already wrote the algorithm to do this in the console, but I want to make a JApplet that pops up and animates the puzzle being solved after I ask for the number of disks. Here is my code for the algorithm if that helps. Just looking for some instruction, no need to write out the entire code. Thanks.
This is my code for the algorithm.
public class TowerofHanoi extends JFrame{
static int count= 0;
public void move(int n, String start, String auxiliary, String end) {
if (n == 1) {
count++;
System.out.println(start + " -> " + end);
} else {
count++;
move(n - 1, start, end, auxiliary);
System.out.println(start + " -> " + end);
move(n - 1, auxiliary, start, end);
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
TowerofHanoi towersOfHanoi = new TowerofHanoi();
System.out.print("Enter number of discs: ");
Scanner scanner = new Scanner(System.in);
int discs = scanner.nextInt();
towersOfHanoi.move(discs, "A", "B", "C");
System.out.println("This puzzle took "+count+" moves.");
}
public void paint(Graphics g) {
g.drawRect (10, 10, 200, 200);
}
public TowerofHanoi(){
setPreferredSize(new Dimension(WIDTH, HEIGHT));
}
}
This is my code for the JApplet.
public class Graphics_TOH {
public static void main(String[] args) {
// TODO Auto-generated method stub
JFrame frame = new JFrame ("Draw Person");
frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
TowerofHanoi panel = new TowerofHanoi ();
frame.getContentPane().add(panel);
frame.pack();
frame.setVisible(true);
}
This question is actually a little interesting to me, because it relates to a pet peeve of mine -- the way most programming languages rely on the call stack makes it way too difficult to reuse that nice little move() function of yours.
To do this kind of animation, you need to:
The tricky part for you, of course, is step 3.
Lets say you want to draw one move per second. A refresh happens, you get the current time and find that it's been 4.234 seconds since the start of the animation. You calculate that you are 0.234 seconds into move 4, so you want to draw what it should look like 23.4% of the way through move 4.
In order to do this, you need to know: What discs are static on which pegs during move 4, and which disc is moving, its source peg, and its destination peg.
It would be pretty easy to fix your recursive move function to keep track of all that, BUT since it's going to generate ALL the moves at once, there is no way to have it tell you about move 4 specifically.
To fix this, you basically have 3 choices:
a) You could call your move function at the beginning, and have it record all the moves. Then when you have to draw, you could advance through the recorded moves to the correct one. This is easy, and probably practical. Of course it takes a lot of memory to record all the moves for a big puzzle (1M entries for 20 discs), but it also takes a lot of time to animate that (1 week at one move/sec), so you're not going to animate big puzzles anyway.
b) You could execute your recursive move function in a separate thread that exchanges information with the rendering thread on each redraw. This is actually a pretty common wait to do it in multiplayer games where the game state has to be tracked in "real time" anyway. For you, it is more trouble than it's worth.
c) You could rewrite your hanoi solution in a non-recursive way. Then you could implement an Iterator. This would work a lot like solution (a), but you would advance the iterator to generate new moves when necessary instead of iterating through prerecorded moves. The benefit is that you don't need to generate and store all the moves in advance.
If it were me, I would do solution (c), because I'm pretty comfortable with converting the recursive solution to an iterative one with a separate stack. If you are not comfortable with that sort of thing, then you probably want do do (a) and stuff all the moves into an ArrayList.