Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/*-------------------------------------------------------------------------+
 |                                                                          |
 | Copyright 2005-2011 The ConQAT Project                                   |
 |                                                                          |
 | Licensed under the Apache License, Version 2.0 (the "License");          |
 | you may not use this file except in compliance with the License.         |
 | You may obtain a copy of the License at                                  |
 |                                                                          |
 |    http://www.apache.org/licenses/LICENSE-2.0                            |
 |                                                                          |
 | Unless required by applicable law or agreed to in writing, software      |
 | distributed under the License is distributed on an "AS IS" BASIS,        |
 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
 | See the License for the specific language governing permissions and      |
 | limitations under the License.                                           |
 +-------------------------------------------------------------------------*/

import java.util.ArrayList;

import java.util.List;

public class Main {
    /**
     * Returns the power set of the given input list. Note that elements are
     * treated as unique, i.e. we do not really use set semantics here. Also
     * note that the returned list has 2^n elements for n input elements, so the
     * input list should not be too large.
     */
    public static <T> List<List<T>> getPowerSet(List<T> input) {
        return getPowerSet(input, 0);
    }

    /**
     * Returns the power set of the given input list, only considering elements
     * at or after index <code>start</code>.
     */
    private static <T> List<List<T>> getPowerSet(List<T> input, int start) {
        ArrayList<List<T>> result = new ArrayList<>();
        if (start >= input.size()) {
            result.add(new ArrayList<T>());
        } else {
            T element = input.get(start);
            for (List<T> list : getPowerSet(input, start + 1)) {
                List<T> copy = new ArrayList<>();
                copy.add(element);
                copy.addAll(list);

                result.add(list);
                result.add(copy);
            }
        }
        return result;
    }
}