C++实现一个LRU Cache

#include <iostream>#include <vector>#include <hash_map>using namespace std;using namespace stdext;template<class K, class T>struct LRUCacheEntry{K key;T data;LRUCacheEntry* prev;LRUCacheEntry* next;};template<class K, class T>class LRUCache{private:hash_map< K, LRUCacheEntry<K,T>* >_mapping;vector< LRUCacheEntry<K,T>* >_freeEntries;LRUCacheEntry<K,T> *head;LRUCacheEntry<K,T> *tail;LRUCacheEntry<K,T> *entries;public:LRUCache(size_t size){entries = new LRUCacheEntry<K,T>[size];for (int i=0; i<size; i++)_freeEntries.push_back(entries+i);head = new LRUCacheEntry<K,T>;tail = new LRUCacheEntry<K,T>;head->prev = NULL;head->next = tail;tail->next = NULL;tail->prev = head;}~LRUCache(){delete head;delete tail;delete [] entries;}void put(K key, T data){LRUCacheEntry<K,T>* node = _mapping[key];if(node){// refresh the link listdetach(node);node->data = data;attach(node);}else{if ( _freeEntries.empty() ){node = tail->prev;detach(node);_mapping.erase(node->key);node->data = data;node->key = key;attach(node);}else{node = _freeEntries.back();_freeEntries.pop_back();node->key = key;node->data = data;_mapping[key] = node;attach(node);}}}T get(K key){LRUCacheEntry<K,T>* node = _mapping[key];if(node){detach(node);attach(node);return node->data;}else return NULL;}private:void detach(LRUCacheEntry<K,T>* node){node->prev->next = node->next;node->next->prev = node->prev;}void attach(LRUCacheEntry<K,T>* node){node->next = head->next;node->prev = head;head->next = node;node->next->prev = node;}};int main(){    hash_map<int, int> map;    map[9]= 999;    cout<<map[9]<<endl;    cout<<map[10]<<endl;    LRUCache<int, string> lru_cache(100);    lru_cache.Put(1, "one");    cout<<lru_cache.Get(1)<<endl;    if(lru_cache.Get(2) == "")        lru_cache.Put(2, "two");    cout<<lru_cache.Get(2);    return 0;}

转自：http://www.cs.uml.edu/~jlu1/doc/codes/lruCache.html