caching - 如何存储数百万个缓存，然后追踪 20 个最旧的缓存

Question

我收到一个面试问题，说我需要存储几百万个缓存，然后我需要跟踪 20 个最旧的缓存，一旦缓存收集的阈值增加，就用下一组最旧的缓存替换 20 个最旧的缓存.

I answered to keep a hashmap for it, again the question increases what if we wanna access any of the element on hashmap fastly, how to do, so I told its map so accessing won't be time taking but interviewer was not satisfied. So what should be the idle way for such scenarios.

Answer 1

一个queue非常适合查找和删除最旧的成员。

A queue implemented as a doubly linked list has O(1) insertion and deletion at both ends.

一个priority queue有助于为队列中的不同项目赋予不同的权重(例如，某些队列元素的重新创建成本可能比其他元素更高)。

您可以使用 HashMap 来保存实际元素并根据哈希键快速找到它们，并使用哈希键的队列来跟踪缓存元素的生命周期。