Meeting Room 1 and Meeting Room 2 of Leetcode

                                    Meeting Room 1 and Meeting Room 2 of Leetcode

252. Meeting Rooms

Given an array of meeting time intervals where intervals[i] = [starti, endi], determine if a person could attend all meetings.

Example 1:

Input: intervals = [[0,30],[5,10],[15,20]]
Output: false

Example 2:

Input: intervals = [[7,10],[2,4]]
Output: true

Solution: Sort according to Ending time.

public boolean canAttendMeetings(int[][] intervals) {
       
       Arrays.sort(intervals, (int[] a, int[] b) -> {
         return a[1] - b[1];
       });
       int n = intervals.length;
       for(int i=1;i<n;i++){
        int st = intervals[i][0];
        int en = intervals[i][1];
        if(st < intervals[i-1][1]){
            return false;
        }
       }
       return true;
    }



253. Meeting Rooms II

Given an array of meeting time intervals intervals where intervals[i] = [starti, endi], return the minimum number of conference rooms required.
 
Example 1:
Input: intervals = [[0,30],[5,10],[15,20]]
Output: 2
Example 2:
Input: intervals = [[7,10],[2,4]]
Output: 1

class Solution {
    public int minMeetingRooms(int[][] intervals) {
        List<int[]> events = new ArrayList<>();
        for(int i=0;i<intervals.length;i++) {
            events.add(new int[]{intervals[i][0], i, 0});
            events.add(new int[]{intervals[i][1], i, 1});
        }
        Collections.sort(events, (a, b) -> {
            if(a[0]==b[0]) {
                return b[2]-a[2];
            }
            return a[0] - b[0];
        });
        int rooms = 0;
        int maxRooms = 0;
        // Iterate through the events
        for (int[] event : events) {
            if (event[2] == 0) { // Start of a meeting
                rooms++;
            } else { // End of a meeting
                rooms--;
            }
            maxRooms = Math.max(maxRooms, rooms); 
        }
        return maxRooms;
    }
}

Extended version of this question is
https://leetcode.com/problems/divide-intervals-into-minimum-number-of-groups/description/