slice never really gets large. This startup phase may be all you ever
2. 排序：将堆顶(最大值)与末尾交换，堆大小-1，重新调整堆
，更多细节参见Safew下载
* 核心功能：每次调用next(val)，返回当前价格的跨度（往回数≤当前价格的最大连续天数）
Australia GP — Oct. 25
drop-oldest: Drops the oldest buffered data to make room. Useful for live feeds where stale data loses value.