import java.util.*;

public class Perms <E> {
    Vector<E> insert(E item, int i, Vector<E> v) {
        // Return a new Vector<E> with item inserted into position i of v
        // But leave v untouched so it can be used again
        Vector<E> newV = new Vector<E> (v);
        newV.add(i, item);
        return newV;
    }

    public Vector <Vector <E>> insertAll(E item, Vector <E> v) {
        // Return a vector of vectors with item inserted into all possible
        // positions of v
        Vector <Vector<E>> result = new Vector <Vector<E>>();
        for (int i=0; i<=v.size(); i++) result.add(insert(item, i, v));
        return result;
    }

    public Vector <Vector<E>> permute(Vector<E> v) {
        // Produce a Vector of all the permutations of v
        Vector <Vector<E>> result = new Vector <Vector<E>>();
        if (v.size() == 1) {
            result.add(v);
        }
        else {
            E missing =  v.firstElement();
            Vector<E> rest = new Vector<E>(v);
            rest.remove(0);
            for (Vector<E> thisperm : permute(rest))
                result.addAll(insertAll(missing, thisperm));
        }
        return result;
    }
}