C++设计模式：策略模式

策略模式：定义了算法家族，分别封装起来，然后定义一个统一的借口，算法之间可以相互替换。使用该模式可以让算法的变化不影响到使用算法的客户。

模式实现：策略模式具体实现时通常与工厂模式相结合，定义一个工厂类，来决定初始化哪个算法。

代码如下：

#include<iostream>

using namespace std;


enum RA{LRU,FIFO,RANDOM};

class ReplaceAlgorithm
{
public:
virtual void Replace() = 0;
};


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_ReplaceAlgprithm :public ReplaceAlgorithm
{
public:
void Replace()
    {
        cout << "Random replace algorithm" << endl;
    }
};

class Cache
{
private:
    ReplaceAlgorithm*m_ra;
public:
Cache(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_ReplaceAlgprithm();
        }
else
            m_ra = NULL;
    }
    ~Cache()
    {
        delete m_ra;
        m_ra = NULL;
    }

void Replace()
    {
        m_ra->Replace();
    }
};