public static void main(String args[]){
        char input[] = {'a','b','c','d'};
        CombinationWithStar cws = new CombinationWithStar();
        boolean used[] = new boolean[input.length];
        cws.combine(input, 0, used);
    }
e.g a, b c 
* * *
a * *
a b *
a b c
* b *
* b c
* * c

Idea is to store the index of values in used[] array. So just
like regular combination if used is set print it else print *
src/com/interview/recursion/CombinationWithStar.java