252. Meeting Rooms (Easy)

Given an array of meeting time intervals consisting of start and end times[[s1,e1],[s2,e2],...](si< ei), determine if a person could attend all meetings.

For example,
Given[[0, 30],[5, 10],[15, 20]],
returnfalse.

Solution 1: Arrays.sort O(n log n); O(1)

To determine if a person could attend all meetings, we need to check if the intervals have an overlap.
If an overlap exists, a person could not attend all meetings.

    /**
     * Sort intervals by start time.
     * From second interval, check each interval with the previous one.
     * If current interval's start < previous interval's end, which means an overlap exists, return false.
     */    
    public boolean canAttendMeetings(Interval[] intervals) {
        if (intervals == null || intervals.length <= 1) {
            return true;
        }

//        Arrays.sort(intervals, new Comparator<Interval>() {
//            public int compare(Interval a, Interval b) {
//                return a.start - b.start;
//            }
//        });
        Arrays.sort(intervals, (a, b) -> a.start - b.start);

        for (int i = 1; i < intervals.length; i++) {
            if (intervals[i - 1].end > intervals[i].start) {
                return false;
            }
        }
        return true;
    }

/**
 * Definition for an interval.
 * public class Interval {
 *     int start;
 *     int end;
 *     Interval() { start = 0; end = 0; }
 *     Interval(int s, int e) { start = s; end = e; }
 * }
 */