Class TowersOfHanoi.Move

java.lang.Object

TowersOfHanoi.Move

Enclosing class:

TowersOfHanoi

public static class TowersOfHanoi.Move
extends Object

The Move class represents the action of moving one disc between pegs. Of course, if that disc is covered by other discs, you'll first have to move them off. And after the original disc is moved over, you'll want to put the other discs back on top.

You will need the following fields:

1. A field to hold the disc number
2. Three fields for the to/from/auxiliary pole numbers
3. A field to tell you whether the disc is covered by smaller discs

The last field doesn't have a direct analog to the recursive implementation. However, before the first recursive call the disc in question was covered by a tower of smaller discs. After that recursive call returns, the disc is uncovered and can be moved. Then the second recursive call moved the smaller discs back on top of it.

In the recursive version, the runtime stack keeps track of where in the method to jump back to when the recursive call returned, this effectively keeps a bit of state about how far along the computation is.

In the iterative version, we have to store this information explicitly in the object: is the disc covered (and will require work before it can be moved) or is it now uncovered (and ready to be moved before finally moving the smaller discs back on top).

Constructor Summary

Constructors

Constructor and Description
Move(int disc, int to, int from, int auxiliary, boolean isCovered)

Method Summary

Modifier and Type	Method and Description
String	toString() a string for debugging purposes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Move

public Move(int disc,
            int to,
            int from,
            int auxiliary,
            boolean isCovered)

Parameters:

disc - the current disc

to - which pole the disc is moving to

from - the pole the disc is currently on

auxiliary - the auxiliary pole

isCovered - true if the disc is covered, false otherwise.

Method Detail

toString

public String toString()

a string for debugging purposes. You should print your instance variables. The format is up to you. I would suggest something along the lines of:
"[disc %d, to %d, from %d, auxiliary %d, covered %b]"

Overrides:

toString in class Object

Returns:

string for debugging the iterative version of this program.