public void quicksort(ArrayList<Interval> list, int s, int t) {
		int i = s, j = t;
		Interval temp = list.get(s);
		
		while(i < j) {
			while(i < j && list.get(j).start > temp.start) j--;
			if(i < j) {
				list.set(i, list.get(j));
				i++;
			}
			while(i < j && list.get(i).start < temp.start) i++;
			if(i < j) {
				list.set(j, list.get(i));
				j--;
			}
		}
		list.set(i, temp);
		
		if(s < i-1) quicksort(list, s, i-1);
		if(i+1 < t) quicksort(list, i+1, t);
	}