Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

Create a powerset in Java

Posted on 2011-02-17
6
Medium Priority
?
1,244 Views
Last Modified: 2013-12-14
Hi,

 In Java I want to create a powerset, when i give  a set and a number for the size for e.g.

{1,2,3,4} set:3
------------------
{1,2,3}
{1,2,4}
{1,3,4}
{2,3,4}

or
{1,2,3} set 2
{1,2}
{1,3}
{2,3}

thanks
0
Comment
Question by:kimia_az
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
6 Comments
 
LVL 47

Accepted Solution

by:
for_yan earned 2000 total points
ID: 34922615
0
 
LVL 47

Expert Comment

by:for_yan
ID: 34922622
This implementation is for all sets, I guess it is easy to modify only limiting to
certain size
0
 
LVL 92

Expert Comment

by:objects
ID: 34922645
0
Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

 
LVL 47

Assisted Solution

by:for_yan
for_yan earned 2000 total points
ID: 34922653

This will print only sets of 2 out of {1,2,3}

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class SetUtils {
    public static <T> Set<Set<T>> powerSet(Set<T> originalSet) {
        Set<Set<T>> sets = new HashSet<Set<T>>();
        if (originalSet.isEmpty()) {
            sets.add(new HashSet<T>());
            return sets;
        }
        List<T> list = new ArrayList<T>(originalSet);
        T head = list.get(0);
        Set<T> rest = new HashSet<T>(list.subList(1, list.size()));
        for (Set<T> set : powerSet(rest)) {
            Set<T> newSet = new HashSet<T>();
            newSet.add(head);
            newSet.addAll(set);
            sets.add(newSet);
         
            sets.add(set);
        }

       
        return sets;
    }

    public static void main(String[] args){
    Set<Integer> mySet = new HashSet<Integer>();
    mySet.add(1);
    mySet.add(2);
    mySet.add(3);
    for (Set<Integer> s : SetUtils.powerSet(mySet)) {
        if(s.size() == 2)
        System.out.println(s);
    }

    
}
}

Open in new window

0
 
LVL 47

Expert Comment

by:for_yan
ID: 34922911

This will print only sets of 3 out of {1,2,3,4}  a little bit nicer:


import java.util.*;

public class SetUtils {
    public static <T> Set<Set<T>> powerSet(Set<T> originalSet) {
        Set<Set<T>> sets = new HashSet<Set<T>>();
        if (originalSet.isEmpty()) {
            sets.add(new HashSet<T>());
            return sets;
        }
        List<T> list = new ArrayList<T>(originalSet);
        T head = list.get(0);
        Set<T> rest = new HashSet<T>(list.subList(1, list.size()));
        for (Set<T> set : powerSet(rest)) {
            Set<T> newSet = new HashSet<T>();
            newSet.add(head);
            newSet.addAll(set);
            sets.add(newSet);
         
            sets.add(set);
        }


        return sets;
    }


        public static <T> Set<Set<T>> powerSet1( Set<T>mySet, int n){
                  Set<Set<T>> sets1 = new  HashSet<Set<T>>();
           Set originalSet =  SetUtils.powerSet(mySet);
            Iterator it = originalSet.iterator();
            while(it.hasNext()) {
                Set s = (Set) it.next();
                if(s.size() == n)sets1.add(s);
            }


            return sets1;
        }


    public static void main(String[] args){
    Set<Integer> mySet = new HashSet <Integer>();
    mySet.add(1);
    mySet.add(2);
    mySet.add(3);
     mySet.add(4);    
    for (Set <Integer> s : SetUtils.powerSet1(mySet, 3)) {
               System.out.println(s);
    }

    
}
}

Open in new window

0
 
LVL 4

Expert Comment

by:msk_apk
ID: 34923511
int setLength = 3;
		int[] array = new int[]{1,2,3,4};
		for(int i=0;i<array.length-2;i++)
		{			
			for(int j=i+1;j<array.length -1;j++)
			{
				for(int k=j+1;k<array.length;k++)
				{
					int[] temp = new int[setLength];
					temp[0] = array[i];
					temp[1] = array[j];
					temp[2] = array[k];
					
					System.out.println(temp[0]+","+temp[1]+","+temp[2]);
				}
			}
		}

Open in new window

0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Are you developing a Java application and want to create Excel Spreadsheets? You have come to the right place, this article will describe how you can create Excel Spreadsheets from a Java Application. For the purposes of this article, I will be u…
Introduction This article is the last of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article covers our test design approach and then goes through a simple test case example, how …
THe viewer will learn how to use NetBeans IDE 8.0 for Windows to perform CRUD operations on a MySql database.
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
Suggested Courses

596 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question