1、策略模式（Strategy）

 //抽象接口
 class ReplaceAlgorithm
 {
 public:
     virtual void Replace() = ;
 };
 //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 ;
 }