[C++知识库]c++实现LRU

#include<iostream>
#include<vector>
#include<algorithm>
#include<unordered_map>

using namespace std;

struct DLinkedNode{
    int key, value;
    DLinkedNode* prev;
    DLinkedNode* next;
    DLinkedNode(): key(0), value(0), prev(nullptr), next(nullptr) {}
    DLinkedNode(int _key, int _value): key(_key), value(_value), prev(nullptr), next(nullptr){}
};

class LRUCache{
public:
    LRUCache(int _capacity) : capacity(_capacity), size(0){
        head = new DLinkedNode();
        tail = new DLinkedNode();

        head->next = tail;
        tail->prev = head;
    }

    int get(int key){
        if(cache.count(key)==0) return -1;
        DLinkedNode* node = cache[key];
        movetohead(node);
        return node->value;
    }

    void set(int key, int value){
        if(cache.count(key)>0){
            DLinkedNode* node = cache[key];
            node->value = value;
            movetohead(node);
            
        }else{
            if(size>=capacity){
                DLinkedNode* node = removetail();
                cache.erase(node->key);
                --size;
                delete node;
            }
            DLinkedNode* node = new DLinkedNode(key, value);
            cache[key] = node;
            addtohead(node);
            ++size;
            
        }
    }

    void removeNode(DLinkedNode* node){
        node->prev->next = node->next;
        node->next->prev = node->prev;
    }

    void addtohead(DLinkedNode* node){
        node->prev = head;
        node->next = head->next;
        head->next->prev = node;
        head->next = node;
        
    }

    void movetohead(DLinkedNode* node){
        removeNode(node);
        addtohead(node);
    }
    
    DLinkedNode* removetail(){
        DLinkedNode* node = tail->prev;
        removeNode(node);
        return node;
    }

private:
    unordered_map<int, DLinkedNode*> cache;
    DLinkedNode* head;
    DLinkedNode* tail;
    int size;
    int capacity;
};

int main(){
    LRUCache lru(2);
    vector<vector<int>> oper = {{1,1},{2,2},{1}, {3,3},{2}, {4,4},{1},{3},{4}};

    for(auto op : oper){
        if(op.size()==1){
           int k = lru.get(op[0]);
           cout<<k<<endl;
        }else{
            lru.set(op[0], op[1]);
            cout<<"set:"<<op[0]<<endl;
        }
    }

}