public Vector<Integer> getLeaders() {
        Vector<Integer> leaders = new Vector<Integer>();
        int leaderY = Integer.MAX_VALUE;
        for (int t=0; t<turtles.length; t++) {
            int tY = turtles[t].getY();
            if (tY < leaderY) {
                leaders.clear();
                leaders.add(t+1);
                leaderY = tY;
            } else if (tY == leaderY) {
                if (!leaders.contains(t+1)) {
                    leaders.add(t+1);
                }
            }
        }
        return leaders;
    }