private ArrayList<Card> easyStrategy(ArrayList<Card> cards) {
        ArrayList<Card> toExchange;
        do {

            toExchange = new ArrayList<>();
            for (int i = 0; i < cards.size(); i++) {
                if (random.nextBoolean()) {
                    // losuj karte o indeksie i
                    Card c = randomCard();
                    toExchange.add(c);
                }
            }
        } while (toExchange.size() == cards.size());
        return toExchange;
    }