kimia_az
asked on
Create a powerset in Java
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
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
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
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);
}
}
}
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]);
}
}
}
certain size