【題目描述】LFU (Least Frequently Used) is a famous cache eviction algorithm.For a cache with capacity k,
LRU Chains(or LRU lists)有它們相關的算法在過去已經修改過多次。盡管算法已經修改過，但LRU chain的功能仍然相同:為了幫助被頻繁訪問的buffer內置在cache中和幫助
