public int fileMinMeetingRooms(List<Interval> intervals){
        List<Integer> list = new ArrayList<Integer>();
        Comparator<Integer> comparator = new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                if(Math.abs(o1) == Math.abs(o2)){
                    return o1 - o2;
                }else{
                    return Math.abs(o1) - Math.abs(o2);
                }
            }
        };

        for(Interval interval : intervals){
            list.add(interval.start);
            list.add(-interval.end);
        }
        System.out.println(list);
        Collections.sort(list, comparator);
        System.out.println(list);

        int max = 0;
        int counter = 0;
        for(int i = 0; i < list.size(); i++){
            if(list.get(i) > 0){
                counter++;
            }else{
                counter--;
            }
            max = Math.max(max, counter);
        }
        return max;
    }