How to iteratively generate k elements subsets from a set of size n in java?

Question

I\'m working on a puzzle that involves analyzing all size k subsets and figuring out which one is optimal. I wrote a solution that works when the number of subsets is small,

Answer 1

Here is a combination iterator I wrote recetnly

package psychicpoker;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

import static com.google.common.base.Preconditions.checkArgument;

public class CombinationIterator implements Iterator> {

private int[] indices;
private List elements;
private boolean hasNext = true;

public CombinationIterator(List elements, int k) throws IllegalArgumentException {
    checkArgument(k<=elements.size(), "Impossible to select %d elements from hand of size %d", k, elements.size());
    this.indices = new int[k];
    for(int i=0; i next() {
    Collection result = new ArrayList(indices.length);
    for(int i=indices.length-1; i>=0; i--) {
        result.add(elements.get(indices[i]));
    }
    hasNext = inc();
    return result;
}

public void remove() {
    throw new UnsupportedOperationException();
}

}