code: public int determineMedian(List<Intervalable> intervals)
      {
          int start = -1;
          int end = -1;
          for (Intervalable interval : intervals)
          {
              int currentStart = interval.getStart();
              int currentEnd = interval.getEnd();
              if (start == -1 || currentStart < start)
              {
                  start = currentStart;
              }
              if (end == -1 || currentEnd > end)
              {
                  end = currentEnd;
              }
          }
          return (start + end) / 2;
      }
docs: 计算中点
  @param intervals 区间集合
  @return 中点坐标