private void addNoAdjacent() {
			if (!taken[0] && !taken[1])
				idx.add(0);
			if (!taken[taken.length-2] && !taken[taken.length-1])
				idx.add(taken.length-1);
			for (int i = 1; i < taken.length-1; i++) {
				if (!taken[i-1] && !taken[i] && !taken[i+1])
					idx.add(i);
			}
		}