1、策略模式（Strategy）

//抽象接口  
class ReplaceAlgorithm  
{  
public:  
    virtual void Replace() = 0;  
};  
//三种具体的替换算法  
class LRU_ReplaceAlgorithm : public ReplaceAlgorithm  
{  
public:  
    void Replace() { cout<<"Least Recently Used replace algorithm"<<endl; }  
};  
  
class FIFO_ReplaceAlgorithm : public ReplaceAlgorithm  
{  
public:  
    void Replace() { cout<<"First in First out replace algorithm"<<endl; }  
};  
class Random_ReplaceAlgorithm: public ReplaceAlgorithm  
{  
public:  
    void Replace() { cout<<"Random replace algorithm"<<endl; }  
};  

 

//Cache需要用到替换算法  
enum RA {LRU, FIFO, RANDOM}; //标签  
class Cache  
{  
private:  
    ReplaceAlgorithm *m_ra;  
public:  
    Cache(enum RA ra)   
    {   
        if(ra == LRU)  
            m_ra = new LRU_ReplaceAlgorithm();  
        else if(ra == FIFO)  
            m_ra = new FIFO_ReplaceAlgorithm();  
        else if(ra == RANDOM)  
            m_ra = new Random_ReplaceAlgorithm();  
        else   
            m_ra = NULL;  
    }  
    ~Cache() { delete m_ra; }  
    void Replace() { m_ra->Replace(); }  
};  

 

int main()  
{  
    Cache cache(LRU); //指定标签即可  
    cache.Replace();  
    return 0;  
}