[LC] 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.

Example 1:

Input: [[0, 30],[5, 10],[15, 20]]
Output: 2

Example 2:

Input: [[7,10],[2,4]]
Output: 1

NOTE: input types have been changed on April 15, 2019. Please reset to default code definition to get new method signature.

class Solution {
    public int minMeetingRooms(int[][] intervals) {
        if (intervals == null || intervals.length == 0) {
            return 0;
        }
        int res = 0;
        // need to keep track to current end is
        int end = 0;
        int[] starts = new int[intervals.length];
        int[] ends = new int[intervals.length];
        for (int i = 0; i < intervals.length; i++) {
            starts[i] = intervals[i][0];
            ends[i] = intervals[i][1];
        }
        Arrays.sort(starts);
        Arrays.sort(ends);

        for (int i = 0; i < intervals.length; i++) {
            if (starts[i] < ends[end]) {
                res += 1;
            } else {
                end += 1;
            }
        }
        return res;
    }
}