[lintcode] problem 920 – meeting rooms

public class  {
    int start, end;

    Interval(int start, int end) {
        this.start = start;
        this.end = end;
    }
}

public boolean canAttendMeetings(List<Interval> intervals) {
    if (intervals == null || intervals.size() < 1)
        return true;
        
    Collections.sort(intervals, new Comparator<Interval>() {
        
        public int compare(Interval o1, Interval o2) {
            return o1.start - o2.start;
        }
    });
    
    int end = intervals.get(0).end;

    for (int i = 1; i < intervals.size(); i++) {
        if (intervals.get(i).start < end)
            return false;
            
        end = Math.max(end, intervals.get(i).end);
    }

    return true;
}