LRUCache初步实现

<span style="font-size:18px;"><span style="font-size:18px;background-color: rgb(255, 255, 255);">#ifndef _LRUCACHE_#define _LRUCACHE_#include<hash_map>using namespace std;/*以双链表实现LRUCache，以hash_map为对象容器，提供快速读取。*/template<typename K,typename V>struct LRUCacheNote{LRUCacheNote(K k,V v):key(k),value(v) { prev=nullptr;next=nullptr;}LRUCacheNote():key(K()),value(V()) { prev=nullptr;next=nullptr;}LRUCacheNote* prev;//前驱指针LRUCacheNote* next;//后继指针K key;V value;};template<typename K,typename V>class LRUCache{public:LRUCache(int size):maxsize(size),currentsize(0) {first=nullptr; //即为空链表last=nullptr;}LRUCacheNote<K,V> get(K key);   //取出指定note，并把其移到链表头void put(K key,V value);       //插入一个节点到链表头void remove(K key);          //删除指定节点void removelast();          //删除最久没被用到的节点（链表尾节点）void MvoeToHead(LRUCacheNote<K,V>& note);//指定节点移到链表头void clear();            //清空容器int capcity(){return this->currentsize;}; //返回当前容量hash_map<K,LRUCacheNote<K,V>* >& getmap(){return this->map;}  //返回对象容器LRUCacheNote<K,V>* getfirst(){return this->first;}             //获取头指针LRUCacheNote<K,V>* getlast(){return this->last;}//获取尾部指针private:LRUCacheNote<K,V>* first;//头结点指针    LRUCacheNote<K,V>*  last;//尾节点指针const int maxsize;//对象容器最大容量int  currentsize;//当前容器容量hash_map<K,LRUCacheNote<K,V>* > map;//对象容器    存入节点指针而非节点对象</span></span>

<span style="font-size:18px;"><span style="font-size:18px;background-color: rgb(255, 255, 255);">};/***********************************************************************///LRUCache方法实现：template<typename K,typename V>LRUCacheNote<K,V> LRUCache<K,V>::get(K key){LRUCacheNote<K,V>* note=map.at(key);if(this->map.find(key)!=this->map.end()){this->MvoeToHead(*note);return *note;}else{cout<<"This list is empty!";return LRUCacheNote<K,V>();}}template<typename K,typename V>void  LRUCache<K,V>::put(K key,V value){LRUCacheNote<K,V>* pnote=new LRUCacheNote<K,V>(key,value);if(this->map.find(key)!=map.end())//元素已有，则直接移到头部        {this->MvoeToHead(*pnote);         return ;    } else if(this->currentsize==0)//没有则插入到头部,原来为空链表{this->first=pnote;this->last=pnote;++(this->currentsize);this->map.insert(make_pair(key,pnote));//注意插入的是 拷贝}else//原来非空{pnote->prev=first;this->first->next=pnote;this->first=pnote;++(this->currentsize);this->map.insert(make_pair(key,pnote));}   if(this->currentsize > this->maxsize)//容器溢出，删除尾元素 this->removelast();}template<typename K,typename V>void  LRUCache<K,V>::MvoeToHead(LRUCacheNote<K,V>& note){if(note.key==this->first->key)//已经在头部 return;else if(note.key==this->last->key)//在尾部{  note.next->prev=note.prev;this->last=note.next;   note.prev=this->first;  // this->first->prev=¬e;   this->first->next=¬e;   note.next=nullptr;   this->first=¬e;}else//不在头尾{note.next->prev=note.prev;note.prev->next=note.next;   note.prev=this->first;  // this->first->prev=¬e;   this->first->next=¬e;   note.next=nullptr;   this->first=¬e;}}template<typename K,typename V>void  LRUCache<K,V>::removelast(){if(first==nullptr)//空链表return ;else if(this->first==this->last)//只有一个节点{LRUCacheNote<K,V>* p=this->last;this->first=nullptr;this->last=nullptr;this->map.erase(p->key);    --(this->currentsize);}else{LRUCacheNote<K,V>* p=this->last;(this->last->next)->prev=nullptr;this->last=this->last->next;this->map.erase(p->key);        --(this->currentsize);}}template<typename K,typename V>void  LRUCache<K,V>::remove(K key){if(first==nullptr)//空链表return ;else{ LRUCacheNote<K,V>& note=*(this->map.at(key)); if(this->map.find(key)==map.end())//不存在该节点 return;  else   { if(this->first==this->last)//只有一个节点{this->first=nullptr;this->last=nullptr;} else if(key==this->first->key)//为头节点   {  // note.prev->next=note.next;   note.prev->next=note.next;   this->first=note.prev;   } else if(key==this->last->key)//为尾节点 { note.next->prev=nullptr; this->last=note.next;  } else { note.next->prev=note.prev; note.prev->next=note.next;    }this->map.erase(key); --(this->currentsize); }}}template<typename K,typename V>void  LRUCache<K,V>::clear(){this->first=nullptr;this->last=nullptr;this->map.clear();this->currentsize=0;}#endif </span></span>

<span style="font-size:18px;"></pre><pre name="code" class="cpp"><span style="font-size:18px;background-color: rgb(255, 255, 255);">/*******************************基本功能测试*********************************************/<pre name="code" class="cpp">#include"LRUCache.h"#include<iostream>#include<string>using namespace std;int main(){string s1="aaa";string s2="bbb";string s3="ccc";LRUCache<int,string> l(5);l.put(1,s1);l.put(2,s2);l.put(3,s3);l.put(4,"ddd");//从链表输出LRUCacheNote<int,string>* p1=l.getfirst();for(int i=0;i<l.capcity();++i){cout<<p1->value<<endl;p1=p1->prev;}//从hash_map输出for(auto i:l.getmap())cout<<i.second->value<<endl;//移到头部cout<<"MvoeToHead:"<<endl;l.MvoeToHead(*(l.getmap().begin()->second));LRUCacheNote<int,string>* p2=l.getfirst();for(int i=0;i<l.capcity();++i){cout<<p2->value<<endl;     p2=p2->prev;}//读取指定key节点cout<<"get(3):"<<l.get(3).value<<endl;LRUCacheNote<int,string>* p3=l.getfirst();for(int i=0;i<l.capcity();++i){cout<<p3->value<<endl;     p3=p3->prev;}//删除节点cout<<"remove(2):"<<endl;l.remove(2);LRUCacheNote<int,string>* p4=l.getfirst();for(int i=0;i<l.capcity();++i){cout<<p4->value<<endl;     p4=p4->prev;}//从hash_map输出for(auto i:l.getmap())cout<<i.second->value<<endl;l.put(100,"are you ok?");//从链表输出cout<<"put():"<<endl;LRUCacheNote<int,string>* p5=l.getfirst();for(int i=0;i<l.capcity();++i){cout<<p5->value<<endl;     p5=p5->prev;}//链表逆向输出LRUCacheNote<int,string>* p6=l.getlast();for(int i=0;i<l.capcity();++i){cout<<p6->value<<endl;p6=p6->next;}//从hash_map输出for(auto i:l.getmap())cout<<i.second->value<<endl;}</span></span>

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