[lintcode] problem 919 – meeting rooms ii

public class  {
    int start, end;

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

public int minMeetingRooms(List<Interval> intervals) {
    if (intervals == null || intervals.size() < 1)
        return 0;

    Collections.sort(intervals, new Comparator<Interval>() {
        
        public int compare(Interval o1, Interval o2) {
            return o1.start - o2.start;
        }
    });

    PriorityQueue<Integer> minHeap = new PriorityQueue<>();
    minHeap.offer(intervals.get(0).end);

    for (int i = 1; i < intervals.size(); i++) {
        if (intervals.get(i).start > minHeap.peek())
            minHeap.poll();

        minHeap.offer(intervals.get(i).end);
    }
    
    return minHeap.size();
}