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JGraphT is a free Java graph library that provides mathematical graph-theory objects and algorithms
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/* ==========================================
 * JGraphT : a free Java graph-theory library
 * ==========================================
 *
 * Project Info:  http://jgrapht.sourceforge.net/
 * Project Creator:  Barak Naveh (http://sourceforge.net/users/barak_naveh)
 *
 * (C) Copyright 2003-2007, by Barak Naveh and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library 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 Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */
/* -----------------
 * CollectionPermutationIter.java
 * -----------------
 * (C) Copyright 2005-2007, by Assaf Lehr and Contributors.
 *
 * Original Author:  Assaf Lehr
 * Contributor(s):   -
 *
 * $Id: CollectionPermutationIter.java 580 2008-01-02 05:05:00Z perfecthash $
 *
 * Changes
 * -------
 */
package org.jgrapht.experimental.permutation;

import java.util.*;


/**
 * Given a container with elements (Collection,Enumeration,array) defines a
 * permutation iterator which returns, on each iteration, a differnt permutation
 * of the source container. You may choose a different container
 * type(Collection/Array/etc) for each next call. It will continue as if they
 * were the same iterator.
 *
 * @author Assaf
 * @since May 20, 2005
 */
public class CollectionPermutationIter
{
    //~ Instance fields --------------------------------------------------------

    private ArrayPermutationsIter permOrder;
    private List sourceArray;

    /**
     * change everry calculation.can be retrieved publicly
     */
    private int [] currPermutationArray;

    //~ Constructors -----------------------------------------------------------

    /**
     * Note: the Set interface does not guarantee iteration order. This method
     * iterates on the set to get the initial order and after that the data will
     * be saved internally in another (ordered) container. So, remeber that the
     * Initial order can be different from the objectSet.toString() method. If
     * you want it to be the same, use a LinkedHashSet , or use the array
     * constructor.
     *
     * @param objectsSet
     */
    public CollectionPermutationIter(Set objectsSet)
    {
        this(
            new ArrayList(objectsSet),
            new IntegerPermutationIter(objectsSet.size()));
    }

    /**
     * Uses a permArray like [1,1,1,2] where some of the permutations are not
     * relevant. Here there will be 4 permutations (only the '2' position is
     * important)
     *
     * @param objectsArray
     * @param permuter
     */
    public CollectionPermutationIter(List objectsArray)
    {
        this(
            objectsArray,
            new IntegerPermutationIter(objectsArray.size()));
    }

    public CollectionPermutationIter(
        List objectsArray,
        ArrayPermutationsIter permuter)
    {
        this.permOrder = permuter;
        this.sourceArray = objectsArray;
    }

    //~ Methods ----------------------------------------------------------------

    public boolean hasNext()
    {
        return this.permOrder.hasNextPermutaions();
    }

    /**
     * On first call, returns the source as an array; on any other call
     * thereafter, a new permutation
     *
     * @return null if we overflowed! the array otherwise
     */
    public List getNextArray()
    {
        List permutationResult; // will hold the array result
        if (this.permOrder.hasNextPermutaions()) {
            this.currPermutationArray = this.permOrder.nextPermutation();
            permutationResult = applyPermutation();
        } else {
            permutationResult = null;
        }

        return permutationResult;
    }

    private List applyPermutation()
    {
        ArrayList output = new ArrayList(sourceArray);

        // Example : this.sourceArray = ["A","B","C","D"]
        // perOrder:                  = [ 1 , 0 , 3 , 2 ]
        // result  :                  = ["B","A","D","C"]
        for (int i = 0; i < output.size(); i++) {
            output.set(
                i,
                this.sourceArray.get(this.currPermutationArray[i]));
        }
        return output;
    }

    /**
     * Wrap result to a Set.
     *
     * @return null if we overflowed! the set otherwise
     */
    public Set getNextSet()
    {
        List result = getNextArray();
        if (result == null) {
            return null;
        } else // wrap in a SET
        {
            Set resultSet = new LinkedHashSet(result);
            return resultSet;
        }
    }

    public int [] getCurrentPermutationArray()
    {
        return this.currPermutationArray;
    }

    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        sb.append("Permutation int[]=");
        sb.append(Arrays.toString(getCurrentPermutationArray()));

        List permutationResult = applyPermutation();
        sb.append("\nPermutationSet Source Object[]=");
        sb.append(this.sourceArray.toString());
        sb.append("\nPermutationSet Result Object[]=");
        sb.append(permutationResult.toString());
        return sb.toString();
    }
}

// End CollectionPermutationIter.java