Iterative Cartesian Product in Java

Question

I want to compute the cartesian product of an arbitrary number of nonempty sets in Java.

I\'ve wrote that iterative code...

public s         


        

Answer 1

You might be interested in Another question about cartesian products (edit: removed to conserve hyperlinks, search for the tag cartesian products). That answer has a nice recursive solution that I'd be hard pressed to improve on. Do you specifically want an iterative solution instead of recursive solution?

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EDIT:

After looking at another iterative solution on stack overflow in perl and a clean explanation , here is another solution:

public static  List> uglyCartesianProduct(List> list) {
        List> iterators = new ArrayList>(list.size());
        List elements = new ArrayList(list.size());
        List> toRet = new ArrayList>();

        for (int i = 0; i < list.size(); i++) {
            iterators.add(list.get(i).iterator());
            elements.add(iterators.get(i).next());
        }

        for(int i = 0; i < numberOfTuples(list); i++)
        {
            toRet.add(new HashSet());
        }

        int setIndex = 0;
        for (Set set : list) {
            int index = 0;
            for (int i = 0; i < numberOfTuples(list); i++) {
                toRet.get(index).add((T) set.toArray()[index % set.size()]);
                index++;
            }
            setIndex++;
        }

        return toRet;
    }

    private static  int numberOfTuples(List> list) {
        int product = 1;
        for (Set set : list) {
            product *= set.size();
        }
        return product;
    }