Interval time comparison_longest continuous interval

This question comes from an interview question: the leader held a meeting, listed several dates, and asked the dates to hold up to several meetings. I knew the general idea at the time, but I didn’t write it out at the first time. Then I thought about it and wrote it at night. This article is for reference only

For example:

[9:00,10:20]", "[10:10,10:50]", "[10:21,10:50]", "[11:20,12:30]

Core idea: Convert the time interval to a digital interval, because the time itself is converted to a millisecond value of long type

    private static LinkedList<LinkedList<List<Long>>> result = new LinkedList<>();
    public static void main(String[] args) throws Exception {
        List<String> list = Arrays.asList("[9:00,10:20]", "[10:10,10:50]", "[10:21,10:50]", "[11:20,12:30]");
        LinkedList<List<Long>> nums = new LinkedList<>();
        for (String s : list) {
            String replace1 = s.replace("[", "").replace("]", "");
            String[] split = replace1.split(",");
            SimpleDateFormat format = new SimpleDateFormat("HH:mm");
            Date parse = format.parse(split[0]);
            Date parse2 = format.parse(split[1]);
            List<Long> longs = new ArrayList<>();
            longs.add(parse.getTime());
            longs.add(parse2.getTime());
            nums.add(longs);
        }
        System.out.println(nums);
        backTrack(nums, new LinkedList<List<Long>>(), 0);
        System.out.println(result);
        for (LinkedList<List<Long>> lists : result) {
            System.out.println(lists.size());
        }

    }
    public static void backTrack(LinkedList<List<Long>> nums,LinkedList<List<Long>> tmp,int num){
        if (tmp != null && tmp.size() > 1) {
            List<Long> longs = tmp.get(tmp.size()-2);
            List<Long> longs2 = tmp.get(tmp.size()-1);
            Long aLong = longs.get(1);
            Long aLong1 = longs2.get(0);
            if (aLong1 < aLong) {
                return;
            }else {
                result.add(new LinkedList<>(tmp));
            }
        }
        for (int i = num; i <nums.size() ; i++) {
            tmp.add(nums.get(i));
            backTrack(nums, tmp, i + 1);
            tmp.removeLast();
        }
    }
    

convert to milliseconds

//[9:00,10:20]", "[10:10,10:50]", "[10:21,10:50]", "[11:20,12:30]

[[3600000, 8400000], [7800000, 10200000], [8460000, 10200000], [12000000, 16200000]]

So the problem becomes the problem of finding the largest continuous subinterval

find all series

[

[[3600000, 8400000], [8460000, 10200000]]

, [[3600000, 8400000], [8460000, 10200000], [12000000, 16200000]]

, [[3600000, 8400000], [12000000, 16200000]]

, [[7800000, 10200000], [12000000, 16200000]]

, [[8460000, 10200000], [12000000, 16200000]]

]

final result range

[[3600000, 8400000], [8460000, 10200000], [12000000, 16200000]]

//[9:00,10:20]", "[10:21,10:50]", "[11:20,12:30]