Java List Permutate permute(List list1)

Description

Create a list of all permutations (lists) of the elements within the given list.

License

Open Source License

Declaration

public static <E> List<List<E>> permute(List<E> list1) 

Method Source Code

//package com.java2s;
/*/*w ww  .j av  a2  s.  co  m*/
Copyright 2009 Semantic Discovery, Inc. (www.semanticdiscovery.com)
    
This file is part of the Semantic Discovery Toolkit.
    
The Semantic Discovery Toolkit 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 3 of the License, or
(at your option) any later version.
    
The Semantic Discovery Toolkit 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 The Semantic Discovery Toolkit.  If not, see <http://www.gnu.org/licenses/>.
*/

import java.util.List;
import java.util.ArrayList;
import java.util.LinkedList;

import java.util.Iterator;

public class Main {
    /**
     * Create a list of all permutations (lists) of the elements within
     * the given list.
     */
    public static <E> List<List<E>> permute(List<E> list1) {
        List<List<E>> result = new ArrayList<List<E>>();

        if (list1 != null) {
            int s1 = list1.size();

            if (s1 > 0) {
                int index = 0;
                for (Iterator<E> it = list1.iterator(); it.hasNext(); ++index) {
                    E elt = it.next();
                    List<E> list2 = new LinkedList<E>(list1.subList(0, index));
                    list2.addAll(list1.subList(index + 1, s1));
                    List<List<E>> p2 = permute(list2);

                    for (List<E> curList : p2) {
                        ((LinkedList<E>) curList).addFirst(elt);
                        result.add(curList);
                    }
                }
            } else {
                result.add(new LinkedList<E>());
            }
        }

        return result;
    }
}

Related

1. permutations(List list)
2. permutations(List listings)
3. permutations(Map> parameterValues)
4. permute(List s1, List s2)
5. permute(List arr)
6. permute(List list, int index, List> result)
7. permute(T[] arr, List p)
8. permutedGroups(List> elementLists)
9. permuteList(List list, int[] permutations)