code: //==============================================================================
  //	
  //	Copyright (c) 2002-
  //	Authors:
  //	* Dave Parker <david.parker@comlab.ox.ac.uk> (University of Oxford)
  //	
  //------------------------------------------------------------------------------
  //	
  //	This file is part of PRISM.
  //	
  //	PRISM 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.
  //	
  //	PRISM 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 PRISM; if not, write to the Free Software Foundation,
  //	Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  //	
  //==============================================================================
  
  package explicit;
  
  import java.util.*;
  
  /**
   * Class storing an indexed set of objects of type T.
   * Typically used for storing state space during reachability.
   */
  public class IndexedSet<T> implements StateStorage<T>
  {
  	protected Map<T, Integer> set;
  	protected int indexOfLastAdd;
  
  	public IndexedSet()
  	{
  		this(false);
  	}
  
  	public IndexedSet(boolean sorted)
  	{
  		indexOfLastAdd = -1;
  		set = sorted ? new TreeMap<T, Integer>() : new HashMap<T, Integer>();
  	}
  	
  	public IndexedSet(Comparator<T> comparator)
  	{
  		indexOfLastAdd = -1;
  		set = new TreeMap<T, Integer>(comparator);
  	}
  
  	@Override
  	public void clear()
  	{
  		set.clear();
  	}
  	
  	@Override
  	public boolean add(T state)
  	{
  		Integer i = set.get(state);
  		if (i != null) {
  			indexOfLastAdd = i;
  			return false;
  		} else {
  			indexOfLastAdd = set.size();
  			set.put(state, set.size());
  			return true;
  		}
  	}
  
  	@Override
  	public boolean contains(T state)
  	{
  			return set.get(state) != null;
  	}
  
  	@Override
  	public int getIndexOfLastAdd()
  	{
  		return indexOfLastAdd;
  	}
  
  	@Override
  	public boolean isEmpty()
  	{
  		return set.isEmpty();
  	}
  
  	/**
  	 * Get the number of objects stored in the set.
  	 */
  	@Override
  	public int size()
  	{
  		return set.size();
  	}
  
  	/**
  	 * Get access to the underlying set of map entries. 
  	 */
  	@Override
  	public Set<Map.Entry<T, Integer>> getEntrySet()
  	{
  		return set.entrySet();
  	}
  	
  	/**
  	 * Create an ArrayList of the states, ordered by index.
  	 */
  	@Override
  	public ArrayList<T> toArrayList()
  	{
  		ArrayList<T> list = new ArrayList<T>(set.size());
  		toArrayList(list);
  		return list;
  	}
  
  	/**
  	 * Create an ArrayList of the states, ordered by index, storing in the passed in list.
  	 * @param list An empty ArrayList in which to store the result.
  	 */
  	@Override
  	public void toArrayList(ArrayList<T> list)
  	{
  		int i, n;
  
  		n = set.size();
  		for (i = 0; i < n ; i++)
  			list.add(null);
  		for (Map.Entry<T, Integer> e : set.entrySet()) {
  			list.set(e.getValue(), e.getKey());
  		}
  	}
  	
  	/**
  	 * Create an ArrayList of the states, ordered by permuted index.
  	 * Index in new list is permut[old_index].
  	 * @param permut Permutation to apply
  	 */
  	@Override
  	public ArrayList<T> toPermutedArrayList(int permut[])
  	{
  		ArrayList<T> list = new ArrayList<T>(set.size());
  		toPermutedArrayList(permut, list);
  		return list;
  	}
  
  	/**
  	 * Create an ArrayList of the states, ordered by permuted index, storing in the passed in list.
  	 * Index in new list is permut[old_index].
  	 * @param permut Permutation to apply
  	 * @param list An empty ArrayList in which to store the result.
  	 */
  	@Override
  	public void toPermutedArrayList(int permut[], ArrayList<T> list)
  	{
  		int i, n;
  
  		n = set.size();
  		for (i = 0; i < n ; i++)
  			list.add(null);
  		for (Map.Entry<T, Integer> e : set.entrySet()) {
  			list.set(permut[e.getValue()], e.getKey());
  		}
  	}
  	
  	/**
  	 * Build sort permutation. Assuming this was built as a sorted set,
  	 * this returns a permutation (integer array) mapping current indices
  	 * to new indices under the sorting order.
  	 */
  	@Override
  	public int[] buildSortingPermutation()
  	{
  		int i, n;
  		int perm[];
  		
  		n = set.size();
  		perm = new int[n];
  		i = 0;
  		for (Map.Entry<T, Integer> e : set.entrySet()) {
  			perm[e.getValue()] = i++;
  		}
  		
  		return perm;
  	}
  	
  	@Override
  	public String toString()
  	{
  		return set.toString();
  	}
  
  	@Override
  	public int get(T t)
  	{
  		return set.get(t);
  	}
  }
  