ai.search
Class Puzzle8Problem

java.lang.Object
  ai.search.Problem
      ai.search.Puzzle8Problem

All Implemented Interfaces:

java.awt.event.ActionListener, java.util.EventListener, java.lang.Runnable

public class Puzzle8Problem

extends Problem

implements java.awt.event.ActionListener

The 8-puzzle Problem In this implementation of the 8-puzzle we have a mix of priorities between efficiency and simplicity. The representation of states is not the obvious one (a 3x3 array), but it is both efficient and fairly easy to manipulate. We represent each tile as an integer from 0 to 8, arranged as follows: 0 1 2 3 4 5 6 7 8 Finally, we represent a state (i.e. a complete puzzle) as the sum of the tile numbers times 9 to the power of the tile's square number. For example, the state state from p63: 1 2 3 1*9^0 + 2*9^1 + 3*9^2 8 . 4 is represented by: + 8*9^3 + 0*9^4 + 4*9^5 7 6 5 + 7*9^6 + 6*9^7 + 5*9^8 = 247893796 We represent actions with the four symbols <, >, ^, V to stand for moving the blank tile left, right, up and down respectively.

Author:

Jill Zimmerman -- jill.zimmerman@goucher.edu

Field Summary

Fields inherited from class ai.search.Problem

algorithm, canvas, currentNode, display, goal, heuristic, initialState, numExpanded, q, search, searchResult

Method Summary

void	actionPerformed(java.awt.event.ActionEvent e)
java.lang.String	actionToString(java.lang.Object action) Convert an action to a string.
boolean	equalState(java.lang.Object state1, java.lang.Object state2) Determine if two states are equivalent.
boolean	goalReached(java.lang.Object state) Is the state a goal state?
int	hCost(java.lang.Object state) Estimate the number of moves to the goal using heuristic.
java.lang.String	stateToString(java.lang.Object state) Convert a state to a string.
java.util.Vector	successors(java.lang.Object state) Determine all the states which are successors of the given state.

Methods inherited from class ai.search.Problem

edgeCost, run, solve, start, stop

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

goalReached

public boolean goalReached(java.lang.Object state)

Is the state a goal state?

Overrides:

goalReached in class Problem

successors

public java.util.Vector successors(java.lang.Object state)

Determine all the states which are successors of the given state.

Specified by:

successors in class Problem

Parameters:

state - is the given state

Returns:

a vector of successors

hCost

public int hCost(java.lang.Object state)

Estimate the number of moves to the goal using heuristic.

Overrides:

hCost in class Problem

Parameters:

state - is the given state

equalState

public boolean equalState(java.lang.Object state1,
                          java.lang.Object state2)

Description copied from class: Problem

Determine if two states are equivalent.

Specified by:

equalState in class Problem

Parameters:

state1 - and states are the two states

Returns:

true if equal

stateToString

public java.lang.String stateToString(java.lang.Object state)

Description copied from class: Problem

Convert a state to a string.

Specified by:

stateToString in class Problem

Parameters:

state - is the given state

Returns:

a string expressing the state

actionToString

public java.lang.String actionToString(java.lang.Object action)

Description copied from class: Problem

Convert an action to a string.

Specified by:

actionToString in class Problem

Parameters:

action - is the given action

Returns:

a string expressing the action

actionPerformed

public void actionPerformed(java.awt.event.ActionEvent e)

Specified by:

actionPerformed in interface java.awt.event.ActionListener

Overrides:

actionPerformed in class Problem