[LeetCode 253] Meeting Rooms II

Given an array of meeting time intervals consisting of start and end times  [[s1,e1], [s2,e2],...]  (si < ei), find the minimum number of conference rooms required.
For example, Given  [[0, 30],[5, 10],[15, 20]] , return  2 .
solution:
put start and negative end into list, sort it based on the absolute value. use two variable to record minimum meeting room

public int minMeetingRooms(Interval[] intervals) {
        int res = 0;
        if(intervals.length == 0) return res;
        if(intervals.length == 1) return res+1;
        List points = new ArrayList<>();
        for(int i=0;i() {
            public int compare(Integer o1, Integer o2) {
                return Math.abs(o1) - Math.abs(o2);
            }
        });
        int local = 0;
        for(int i=0;i=0) {
                local++;
            }
            else local--;
            res = Math.max(local, res);
        }
        return res;
    }