public int findMinimumMeetingRooms(List<Meeting> meetings) {
    int overlap = 0, maxOverlap = 0, n = meetings.size();
    if(n==0) return 0;
    meetings.sort((a,b)->Integer.compare(a.start,b.start));

    Meeting curr = meetings.get(0);
    int start = curr.start, end = curr.end;
    for(int i = 1; i < n; i++) {
      curr = meetings.get(i);
      if(end > curr.start) {
        overlap++;
        maxOverlap = Math.max(maxOverlap, overlap);
      }

      if(curr.end > end) {
        overlap = 0;
        start = curr.start;
        end = curr.end;
      }
    }

    return maxOverlap + 1;
  }