#include <iostream>

 

using namespace std;

 

class StrategyInterface

{

public:

    virtual void execute() = 0;

};

 

class ConcreteStrategyA: public StrategyInterface

{

public:

    virtual void execute()

    {

        cout << "Called ConcreteStrategyA execute method" << endl;

    }

};

 

class ConcreteStrategyB: public StrategyInterface

{

public:

    virtual void execute()

    {

        cout << "Called ConcreteStrategyB execute method" << endl;

    }

};

 

class ConcreteStrategyC: public StrategyInterface

{

public:

    virtual void execute()

    {

        cout << "Called ConcreteStrategyC execute method" << endl;

    }

};

 

class Context

{

private:

    StrategyInterface *_strategy;

 

public:

    Context(StrategyInterface *strategy):_strategy(strategy)

    {

    }

 

    void set_strategy(StrategyInterface *strategy)

    {

        _strategy = strategy;

    }

 

    void execute()

    {

        _strategy->execute();

    }

};

 

int main(int argc, char *argv[])

{

    ConcreteStrategyA concreteStrategyA;

    ConcreteStrategyB concreteStrategyB;

    ConcreteStrategyC concreteStrategyC;

 

    Context contextA(&concreteStrategyA);

    Context contextB(&concreteStrategyB);

    Context contextC(&concreteStrategyC);

 

    contextA.execute();

    contextB.execute();

    contextC.execute();

 

    contextA.set_strategy(&concreteStrategyB);

    contextA.execute();

    contextA.set_strategy(&concreteStrategyC);

    contextA.execute();

 

    return 0;

}