Java List Permutate permutations(List list)

Description

permutations

License

Open Source License

Declaration

static <E> List<List<E>> permutations(List<E> list) 

Method Source Code

//package com.java2s;
/*//from  w ww . j a v  a 2s. c  o  m
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
    static <E> List<List<E>> permutations(List<E> list) {
        return permutations(new ArrayList<E>(), list, new ArrayList<List<E>>());
    }

    static Object[][] permutations(Object... list) {
        List<List<Object>> permutations = permutations(Arrays.asList(list));

        Object[][] a = new Object[permutations.size()][];
        int index = 0;
        for (List<Object> p : permutations) {
            a[index] = p.toArray(new Object[p.size()]);
            index++;
        }

        return a;
    }

    static <E> List<List<E>> permutations(List<E> prefix, List<E> suffix, List<List<E>> output) {
        if (suffix.size() == 1) {
            ArrayList<E> newElement = new ArrayList<>(prefix);
            newElement.addAll(suffix);
            output.add(newElement);
            return output;
        }

        for (int i = 0; i < suffix.size(); i++) {
            List<E> newPrefix = new ArrayList<>(prefix);
            newPrefix.add(suffix.get(i));
            List<E> newSuffix = new ArrayList<>(suffix);
            newSuffix.remove(i);
            permutations(newPrefix, newSuffix, output);
        }

        return output;
    }
}

Related

1. perm(List l)
2. permsList(List topList)
3. permutate(List src)
4. permutation(List list1, List list2, String token)
5. permutation(String prefix, String s, List list)
6. permutations(List listings)
7. permutations(Map> parameterValues)
8. permute(List s1, List s2)
9. permute(List arr)