#include <string>
#include <iostream>
#include <assert.h>
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)
    {
        assert(m_pSaleStrategy != NULL);
        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;
}

#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Singelton
{
private:
	Singelton(){}
	static Singelton* singel;
public:
	static Singelton* GetInstance()
	{
		if(singel == NULL)
		{
			singel = new Singelton();
		}
		return singel;
	}
};
Singelton* Singelton::singel = NULL;//注意静态变量类外初始化
int main()
{
	Singelton* s1=Singelton::GetInstance();
	Singelton* s2=Singelton::GetInstance();
	if(s1 == s2)
		cout<<"ok"<<endl;
	else
		cout<<"no"<<endl;
	return 0;
}

#include<vector>
#include<iostream>
#include<string>
using namespace std;
 
class Subject;
//观察者抽象类
class Observer{                    
public:
  virtual void update(Subject *base)=0;
protected:
  Subject * _subject;
};
//主题抽象类
class Subject{
private:
	//观察者容器
	vector<Observer *> _observer;  
public:
	//数据值，可以作为私有数据，然后定义一个借口去返回值，这里为了省事
	string msg;                        
	void regiObserver(Observer *obs){
	_observer.push_back(obs);
  }
  void deleObserver(Observer *obs){
	  vector<Observer *>::iterator it;
	  for(it = _observer.begin(); it != _observer.end(); it++){
		  if( *it == obs){
			  _observer.erase(it);
			  break;
		  }
	  }
	  
  }
  //通知所有的观察者
  void notify(){                
    vector<Observer *>::iterator it;
    for(it = _observer.begin(); it != _observer.end(); it++)
      (*it)->update(this);
  } 
      
};
//秘书
class SecretarySubject:public Subject{                
public:
	void set(string s){
		msg = s;
		notify();                                   
	}
};
//打游戏的员工
class Gamesobserver :public Observer{    
public:
  Gamesobserver(Subject *base):Observer(){
    _subject = base;
    _subject->regiObserver(this);
  }
  void update(Subject *base){
    msg = base->msg;
    display();
  }
  void display(){
    cout<<msg<<"，关闭游戏界面"<<endl;
  }
private:
  string msg;
};
//炒股票的员工
class StockObserver:public Observer{    
 public:
  StockObserver(Subject * base){
    _subject = base;
    _subject->regiObserver(this);
  }
  void update(Subject *base){
    msg = base->msg;
    display();
  }
   void display(){
    cout<<msg<<"，关闭炒股界面"<<endl;
  }
private:
  string msg;
};
 
int main()
{
  SecretarySubject * sec = new SecretarySubject;
  Gamesobserver * one = new Gamesobserver(sec);
  StockObserver * two = new StockObserver(sec);
  sec->set("老板来了");
  //因为发现打游戏，开除了one
  sec->deleObserver(one);
  sec->set("老板来了");
  return 0;
}