#include <iostream>
using namespace std;

class Strategy {
public:
 virtual void Interface() = 0;
 virtual ~Strategy() { }
};

class ConcreteStrategyA :public Strategy {
public:
 void Interface() {
 cout << "ConcreteStrategyA::Interface..." << endl;
 }
};

class ConcreteStrategyB :public Strategy {
public:
 void Interface() {
 cout << "ConcreteStrategyB::Interface..." << endl;
 }
};

class Context {
public:
 Context(Strategy *stg) {
 _stg = stg;
 }

 void DoAction() {
 _stg->Interface();
 }

private:
 Strategy *_stg;
};

int main() {
 Strategy *ps = new ConcreteStrategyA();
 Context *pc = new Context(ps);
 pc->DoAction();

 delete pc;
 delete ps;

 return 0;
}