strategy模式

讲的很清楚http://www.cnblogs.com/graphicsme/archive/2011/12/03/2274918.html

#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <algorithm>
#include <map>
#include <stack>
using namespace std;

class SaleStrategy {
public:
    virtual float calculate(float price, int amount) = 0;
};

class RegularSaleStrategy: public SaleStrategy {
public:
    virtual float calculate(float price, int amount) {
        return price * amount;
    }
};

class StudentSaleStrategy: public SaleStrategy {
public:
    virtual float calculate(float price, int amount) {
        const float DISCOUNT = 0.5f; //学生半价

        return (1 - DISCOUNT) * price * amount;
    }
};

class BulkSaleStrategy: public SaleStrategy {
public:
    virtual float calculate(float price, int amount) {
        const float DISCOUNT = 0.3f; //批发折扣
        const int BULK_LIMIT = 100; //>=100件按批发价

        if (amount >= BULK_LIMIT)
            return (1 - DISCOUNT) * price * amount;
        return price * amount;
    }
};

class SaleManager {
public:
    SaleManager(SaleStrategy* pSaleStrategy = NULL) :
            m_pSaleStrategy(pSaleStrategy) {
    }

public:
    void setStrategy(SaleStrategy* pSaleStrategy) {
        m_pSaleStrategy = pSaleStrategy;
    }

    float calculateTotal(float price, int amount) {
        float calResult = m_pSaleStrategy->calculate(price, amount);
        cout << "total price is: " << calResult << endl;
        return calResult;
    }

private:
    SaleStrategy* m_pSaleStrategy;
};
int main(int argc, char** argv) {
    SaleStrategy* pSaleStrategy = new RegularSaleStrategy();
    SaleStrategy* pStudentSaleStrategy = new StudentSaleStrategy();
    SaleStrategy* pBulkSaleStrategy = new BulkSaleStrategy();

    SaleManager saleManager(pSaleStrategy);
    cout << "Regular Sale Strategy:\n";
    saleManager.calculateTotal(2.5f, 100);

    saleManager.setStrategy(pStudentSaleStrategy);
    cout << "Student Sale Strategy:\n";
    saleManager.calculateTotal(2.5f, 100);

    saleManager.setStrategy(pBulkSaleStrategy);
    cout << "Bulk Sale Strategy:\n";
    saleManager.calculateTotal(2.5f, 100);

    delete pBulkSaleStrategy;
    delete pStudentSaleStrategy;
    delete pSaleStrategy;

    return 0;
}