### Explanation <img src="https://i.loli.net/2018/09/24/5ba81e5ea9d15.jpg">

minMeetingRooms.java

public int minMeetingRooms(int[][] intervals) {
    int n = intervals.length;
    int[] start = new int[n];
    int[] end = new int[n];
    for(int i = 0; i < n; i++){
        start[i] = intervals[i][0];
        end[i] = intervals[i][1]; 
    }
    Arrays.sort(start);
    Arrays.sort(end);
    int endItr = 0;
    int rooms = 0;
    for(int i = 0; i < n; i++){
        //meeting is starting before the ending of another?
        if(start[i] < end[endItr]){
            rooms++;//if so, we need one more room!
        }
        //meeting starting after(or just after) other ends. No need for another room
        else if(start[i] >= end[endItr]){
            endItr++;//update next ending
        }
    }
    return rooms;
}