定義一組演算法，使得演算法之間具有互換性。

struct Strategy
{
    virtual void AlgorithmInterface() = 0;
};

struct ConcreteStrategyA : Strategy
{
    void AlgorithmInterface() override {}
};

struct ConcreteStrategyB : Strategy
{
    void AlgorithmInterface() override {}
};

struct Context
{
    void ContextInterface()
    {
        _strategy->AlgorithmInterface();
    }

    void SetStrategy(Strategy* strategy) { _strategy = strategy; }
    Context(Strategy* strategy) : _strategy(strategy) {}
private:
    Strategy* _strategy;
};

int main()
{
    Context context(new ConcreteStrategyA);
    context.ContextInterface();//ConcreteStrategyA::AlgorithmInterface() get called

    context.SetStrategy(new ConcreteStrategyB);
    context.ContextInterface();//ConcreteStrategyB::AlgorithmInterface() get called
}