LFU(Least Frequently Used) C++ 实现

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于 2016-01-24 21:36:33 发布 · 2.7k 阅读

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文章标签：

#LFU #Cache #O1

本文介绍了一种LFU（Least Frequently Used）缓存算法的实现细节，采用链表和哈希集合的数据结构来保证插入、删除和查找操作的时间复杂度为O(1)。通过测试程序展示了该算法在特定数据集上的应用。

#include <iostream>
#include <vector>
#include <list>
#include <unordered_map>
#include <unordered_set>
using namespace std;
///////////////////////////////////////////////////////////////////////////////////////////////////////////////
// LFU - Least Frequently Used
class FreqNode{
public:
        int freq;
        // We use a SET in lieu of a linked list for storing elements with the same access frequency
    // for simplicitly of implementation.
        // HASH SET structure which holds the keys of such elements that have the same access frequency.
    // Its insertion, lookup and deletion runtime complexity is O(1).
        unordered_set<int> items;
        FreqNode(int f){
                this->freq = f;
        }
};

// LFU - Least Frequently Used Cache Algorithm
// 1 Linked List + 1 Set + 1 Hash
// O(1) for all: Insert, Delete and Lookup
class LFUCache{
public:
        list<FreqNode*> freqNodes;