/************************************************************************
* Strathclyde Planning Group,
* Department of Computer and Information Sciences,
* University of Strathclyde, Glasgow, UK
* http://planning.cis.strath.ac.uk/
*
* Copyright 2007, Keith Halsey
* Copyright 2008, Andrew Coles and Amanda Smith
*
* (Questions/bug reports now to be sent to Andrew Coles)
*
* This file is part of JavaFF.
*
* JavaFF is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* JavaFF is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with JavaFF. If not, see <http://www.gnu.org/licenses/>.
*
************************************************************************/
package javaff.search;
import javaff.planning.State;
import javaff.planning.Filter;
import java.util.Comparator;
import java.util.Hashtable;
import java.util.LinkedList;
public class BreadthFirstSearch extends Search
{
protected LinkedList open;
protected Hashtable closed;
protected Filter filter = null;
public BreadthFirstSearch(State s)
{
super(s);
open = new LinkedList();
closed = new Hashtable();
}
public void setFilter(Filter f)
{
filter = f;
}
public void updateOpen(State S)
{
open.addAll(S.getNextStates(filter.getActions(S)));
}
public State removeNext()
{
return (State) ((LinkedList) open).removeFirst();
}
public boolean needToVisit(State s) {
Integer Shash = new Integer(s.hashCode());
State D = (State) closed.get(Shash);
if (closed.containsKey(Shash) && D.equals(s)) return false;
closed.put(Shash, s);
return true;
}
public State search() {
open.add(start);
while (!open.isEmpty())
{
State s = removeNext();
if (needToVisit(s)) {
++nodeCount;
if (s.goalReached()) {
return s;
} else {
updateOpen(s);
}
}
}
return null;
}
}