享元模式（Flyweight Pattern）是一种结构设计模式，它通过共享对象来有效地支持大量细粒度的对象。享元模式的目标是尽量减少内存使用，通过共享相同的数据来减少对象的数量。
以下是一个简单的C++享元模式的示例：

#include <iostream>
#include <unordered_map>// 抽象享元类
class Flyweight
{
public:virtual void operation() = 0;
};// 具体享元类
class ConcreteFlyweight : public Flyweight
{
private:std::string intrinsicState;public:ConcreteFlyweight(const std::string &intrinsicState) : intrinsicState(intrinsicState) {}void operation() override{std::cout << "Concrete Flyweight: " << intrinsicState << std::endl;}
};// 享元工厂类
class FlyweightFactory
{
private:std::unordered_map<std::string, Flyweight *> flyweights;public:Flyweight *getFlyweight(const std::string &intrinsicState){if (flyweights.find(intrinsicState) == flyweights.end()){flyweights[intrinsicState] = new ConcreteFlyweight(intrinsicState);}return flyweights[intrinsicState];}~FlyweightFactory(){for (auto it = flyweights.begin(); it != flyweights.end(); ++it){delete it->second;}flyweights.clear();}
};int main()
{FlyweightFactory flyweightFactory;Flyweight *flyweight1 = flyweightFactory.getFlyweight("state1");Flyweight *flyweight2 = flyweightFactory.getFlyweight("state2");Flyweight *flyweight3 = flyweightFactory.getFlyweight("state2");flyweight1->operation();flyweight2->operation();flyweight3->operation();return 0;
}

运行结果：

Concrete Flyweight: state1
Concrete Flyweight: state2
Concrete Flyweight: state2

在上述示例中，Flyweight是抽象享元类，定义了享元对象的接口。ConcreteFlyweight是具体享元类，实现了具体的享元对象。FlyweightFactory是享元工厂类，负责创建和管理享元对象。
在main()函数中，首先创建了一个享元工厂对象flyweightFactory。然后通过调用getFlyweight()方法来获取享元对象。如果工厂中不存在对应的享元对象，则创建一个新的享元对象并将其存储在工厂中；如果已存在对应的享元对象，则直接返回该对象。最后，通过调用享元对象的operation()方法来执行操作。
通过享元模式，可以减少对象的数量，节省内存空间。相同的数据可以被多个对象共享，从而降低了系统的开销。享元模式适用于需要创建大量相似对象的场景，可以提高系统的性能和效率。