Observer mode (C ++)

#include <iostream>#include <string>#include <vector>#include <algorithm>#include <functional>using namespace std;class Observer{public:    Observer(){}    virtual ~Observer(){}    virtual void run()=0;protected:    string _name;};class atlete : public Observer{public:    atlete(string name){_name=name;}    virtual ~atlete(){}    void run()    {        cout<<"atlete "<<_name<<" run"<<endl;    }};class Subject{public:    Subject(){}    virtual void notify()=0;    virtual void attach(Observer*)=0;    virtual void detach(Observer*)=0;protected:    vector<Observer*> vec;};class referee : public Subject{public:    referee(){}    virtual ~referee(){}    void attach(Observer* p)    {        vec.push_back(p);    }    void detach(Observer* p)    {        vec.erase(remove_if(vec.begin(),vec.end(),bind1st(equal_to<Observer*>(),p)));    }    void notify()    {        cout<<"referee say 'run'"<<endl;        vector<Observer*>::iterator it;        for (it=vec.begin();it!=vec.end();it++)        {            (*it)->run();        }    }};int main(){    Observer *pat1=new atlete("zhangsan");    Observer *pat2=new atlete("lisi");    Observer *pat3=new atlete("wangwu");    Subject *pre=new referee;    pre->attach(pat1);    pre->attach(pat2);    pre->attach(pat3);    pre->notify();        cout<<endl;    pre->detach(pat2);    pre->notify();    delete pat1;    delete pat2;    delete pat3;    delete pre;    system("pause");    return 0;}