LRU 实现的四种方式

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最新推荐文章于 2025-04-27 17:21:00 发布

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分类专栏： Algorithm c++ 文章标签：算法 LRU CPP Algorithm

本文链接：https://blog.youkuaiyun.com/hzh_csdn/article/details/93400541

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本文介绍了LRU缓存淘汰策略的四种实现方式，包括单链表、双向链表、unordered_map结合双向链表以及unordered_map结合list。各实现的函数时间复杂度均为O(1)，能有效提高缓存操作效率。

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LRU 实现的四种方式

单链表

class LRUCache {
   
private:
    struct Node {
   
        int key;
        int val;
        Node *next;

        Node(int key, int val) : key(key), val(val), next(nullptr) {
   }
    };

private:
    int capacity;
    Node *pHead;
public:
    LRUCache(int capacity) {
   
        this->capacity = capacity;
        // the size of list is key in head node
        pHead = new Node(0, 0);
    }

    int get(int key) {
   
        Node *pNode = pHead;
        while (nullptr != pNode->next) {
   
            if (key == pNode->next->key) {
   
                // found
                auto tmp = pNode->next;
                pNode->next = pNode->next->next;
                tmp->next = pHead->next;
                pHead->next = tmp;

                return pHead->next->val;
            }
            pNode = pNode->next;
        }
        // not found
        return -1;
    }

    void put(int key, int value) {
   
        Node *pNode = pHead;

        while (nullptr != pNode->next) {
   
            if (key == pNode->next->key) {
   
                pNode->next->val = value;
                auto tmp = pNode->next;
                pNode->next = pNode->next->next;
                tmp->next = pHead->next;
                pHead->next = tmp;
                return;
            }
            pNode = pNode->next;
        }
        // not found
        pNode = new Node(key, value);
        pNode->next = pHead->next;
        pHead->next = pNode;
        pHead->key++;
        if (pHead->key > capacity) {
   
            // remove last node
            pNode = pHead;
            while (nullptr != pNode->next && nullptr != pNode->next->next) {
   
                pNode = pNode->next;
            }
            auto last = pNode->next;
            pNode->next = nullptr;
            if (nullptr != last) {
   
                delete last;
                last == null

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