Leetcode: Meeting Rooms

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]],
return false.

Understand the problem:

The problem looks very similar to the merge interval and insert intervals. So the idea is still the same: first sort the intervals according to the start times, then check if there is any overlap. 

Code (Java):

/**
 * 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; }
 * }
 */
public class Solution {
    public boolean canAttendMeetings(Interval[] intervals) {
        if (intervals == null || intervals.length ==0) {
            return true;
        }
        
        // Sort according to the start time
        Arrays.sort(intervals, new IntervalComparator());
        
        Interval prev = intervals[0];
        for (int i = 1; i < intervals.length; i++) {
            Interval curr = intervals[i];
            if (isOverlapped(prev, curr)) {
                return false;
            }
            prev = curr;
        }
        
        return true;
    }
    
    public class IntervalComparator implements Comparator<Interval> {
        @Override
        public int compare(Interval a, Interval b) {
            return a.start - b.start;
        }
    }
    
    private boolean isOverlapped(Interval a, Interval b) {
        return a.end > b.start;
    }
}