Something

    private void addAllTransformations(int x){
        set.add(listToSkyline(list));
        if(x!=0){
            for(int i=0;i<list.size();i++){
                list.getBuilding(i).moveToLeft();
                addAllTransformations(x-1);
                list.getBuilding(i).moveToRight();
                list.getBuilding(i).moveToRight();
                addAllTransformations(x-1);
                list.getBuilding(i).moveToLeft();
            }
        }
    }