C++中的23种设计模式精讲-拓冰建站

1 单例模式

题目链接为：小明的购物车

C++代码如下，

#include <iostream>
#include <string>
#include <vector>using namespace std;class ShoppingCart {
public:static ShoppingCart& get_instance() {static ShoppingCart instance = ShoppingCart(); //静态变量，类的所有对象共用一个return instance;}vector<string>& get_goods() { return goods;}vector<int>& get_cnt() {return cnt;}void show() {int n = goods.size();for (int i = 0; i < n; ++i) {cout << goods[i] << " " << cnt[i] << endl;}return;}private:ShoppingCart () {} //构造函数私有化，防止外部直接实例化类的对象vector<string> goods; vector<int> cnt; 
};int main() {ShoppingCart& shopping_cart = ShoppingCart::get_instance();string a;int b;while (cin >> a >> b) {shopping_cart.get_goods().emplace_back(a);shopping_cart.get_cnt().emplace_back(b);}shopping_cart.show();return 0;
}

注意要点：

构造函数私有化，防止外部直接实例化ShoppingCart类的对象。
静态变量instance，只会被创建一次，故ShoppingCart类的所有对象共用一个instance。又因为变量instance的类型为ShoppingCart，故该类只会存在一个实例化对象。

2 工厂方法模式

题目链接：积木工厂

C++代码如下，

#include <iostream>
#include <vector>using namespace std;class Block {
public:virtual void produce() = 0;
};class CircleBlock : public Block {void produce() override {cout << "Circle Block" << endl;}
};class SquareBlock : public Block {
public:void produce() override {cout << "Square Block" << endl;}
};class BlockFactory {
public:virtual Block* createBlock() = 0;
};class CircleBlockFactory : public BlockFactory {
public:Block* createBlock() override {return new CircleBlock();}
};class SquareBlockFactory : public BlockFactory {
public:Block* createBlock() override {return new SquareBlock();}
};class BlockFactorySystem {
private:vector<Block*> blocks;public:void produceBlocks(BlockFactory* factory, int quantity) {for (int i = 0; i < quantity; ++i) {Block* block = factory->createBlock();blocks.emplace_back(block);block->produce();}}const vector<Block*>& getBlocks() const {return blocks;} ~BlockFactorySystem() {for (Block* block : blocks) {delete block;}}
};int main() {BlockFactorySystem factorySystem;int productionCount;cin >> productionCount;for (int i = 0; i < productionCount; ++i) {string blockType;int quantity;cin >> blockType >> quantity;if (blockType == "Circle") {factorySystem.produceBlocks(new CircleBlockFactory(), quantity);} else if (blockType == "Square") {factorySystem.produceBlocks(new SquareBlockFactory(), quantity);}}return 0;
}

3 抽象工厂模式

题目链接：家具工厂

C++代码如下，

#include <iostream>
#include <string>using namespace std;class Chair {
public:virtual void showInfo() = 0;
};class ModernChair : public Chair {
public:void showInfo() override {cout << "modern chair" << endl;}
};class ClassicalChair : public Chair {
public:void showInfo() override {cout << "classical chair" << endl;}
};class Sofa {
public:virtual void displayInfo() = 0;
};class ModernSofa : public Sofa {
public:void displayInfo() override {cout << "modern sofa" << endl;}
};class ClassicalSofa : public Sofa {
public:void displayInfo() override {cout <<"classical sofa" << endl;}
};class FurnitureFactory {
public:virtual Chair* createChair() = 0;virtual Sofa* createSofa() = 0;
};class ModernFurnitureFactory : public FurnitureFactory {
public:Chair* createChair() override {return new ModernChair();}Sofa* createSofa() override {return new ModernSofa();}
};class ClassicalFurnitureFactory : public FurnitureFactory {
public:Chair* createChair() override {return new ClassicalChair();}Sofa* createSofa() override {return new ClassicalSofa();}
};int main() {int N;cin >> N;for (int i = 0; i < N; ++i) {string furnitureType;cin >> furnitureType;FurnitureFactory* factory = nullptr;if (furnitureType == "modern") {factory = new ModernFurnitureFactory(); } else if (furnitureType == "classical") {factory = new ClassicalFurnitureFactory();}Chair* chair = factory->createChair();Sofa* sofa = factory->createSofa();chair->showInfo();sofa->displayInfo();delete chair;delete sofa;delete factory;}return 0;
}

4 建造者模式

题目链接为：自行车加工

C++代码如下，

#include <iostream>
#include <string>using namespace std;class Bike {
public:string frame;string tires;void setFrame(const string& frame) {this->frame = frame;}void setTires(const string& tires) {this->tires = tires;}friend ostream& operator<<(ostream& os, const Bike& bike) {os << bike.frame << " " << bike.tires;return os;}
};class BikeBuilder {
public:virtual void buildFrame() = 0;virtual void buildTires() = 0;virtual Bike getResult() = 0;
};class MountainBikeBuilder : public BikeBuilder {
private:Bike bike;
public:void buildFrame() override {bike.setFrame("Aluminum Frame");}void buildTires() override {bike.setTires("Knobby Tires");}Bike getResult() override {return bike;}
};class RoadBikeBuilder : public BikeBuilder {
private:Bike bike;public:void buildFrame() override {bike.setFrame("Carbon Frame");}void buildTires() override {bike.setTires("Slim Tires");}Bike getResult() override {return bike;}
};class BikeDirector {
public:Bike construct(BikeBuilder& builder) {builder.buildFrame();builder.buildTires();return builder.getResult();}
};int main() {int N;cin >> N;BikeDirector director;for (int i = 0; i < N; ++i) {string bikeType;cin >> bikeType;BikeBuilder* builder;if (bikeType == "mountain") {builder = new MountainBikeBuilder();} else {builder = new RoadBikeBuilder();}Bike bike = director.construct(*builder);cout << bike << endl;delete builder;}return 0;
}

5 原型模式

题目链接为：矩阵原型

C++代码如下，

#include <iostream>
#include <string>
#include <vector>class Prototype {
public:virtual Prototype* clone() const = 0;virtual std::string getDetails() const = 0;virtual ~Prototype() {}
};class RectanglePrototype : public Prototype {
private:std::string color;int width;int height;public:RectanglePrototype(std::string color, int width, int height) : color(color), width(width), height(height) {}Prototype* clone() const override {return new RectanglePrototype(*this);}std::string getDetails() const override {return "Color: " + color + ", Width: " + std::to_string(width) + ", Height: " + std::to_string(height);}
};int main() {std::vector<Prototype*> rectangles;int N;std::cin >> N;for (int i = 0; i < N; ++i) {std::string color;int width, height;std::cin >> color >> width >> height;Prototype* originalRectangle = new RectanglePrototype(color, width, height);rectangles.emplace_back(originalRectangle);}for (const auto& rectangle : rectangles) {Prototype* clonedRectangle = rectangle->clone();std::cout << clonedRectangle->getDetails() << std::endl;delete clonedRectangle;}for (const auto& rectangle : rectangles) {delete rectangle;}return 0;
}

6 适配器模式

题目链接为：扩展坞

C++代码如下，

#include <iostream>class USB {
public:virtual void charge() = 0;
};class TypeC {
public:virtual void chargeWithTypeC() = 0;
};class TypeCAdapter : public USB {
private:TypeC* typeC;public:TypeCAdapter(TypeC* typeC) : typeC(typeC) {}void charge() override {typeC->chargeWithTypeC();}
};class NewComputer : public TypeC {
public:void chargeWithTypeC() override {std::cout << "TypeC" << std::endl;}
};class AdapterCharger : public USB {
public:void charge() override {std::cout << "USB Adapter" << std::endl;}
};int main() {int N;std::cin >> N;//std::cin.ignore();for (int i = 0; i < N; ++i) {int choice;std::cin >> choice;if (choice == 1) {TypeC* newComputer = new NewComputer();newComputer->chargeWithTypeC();delete newComputer;} else if (choice == 2) {USB* usbAdapter = new AdapterCharger();usbAdapter->charge();delete usbAdapter;}}return 0;
}

7 代理模式

题目链接为：小明买房子

C++代码如下，

#include <iostream>//抽象主题
class HomePurchase {
public:virtual void requestPurchase(int area) = 0;
};//真实主题
class HomeBuyer : public HomePurchase {
public:void requestPurchase(int area) override {std::cout << "YES" << std::endl;}
};//代理类
class HomeAgentProxy : public HomePurchase {
private:HomeBuyer homeBuyer;public:void requestPurchase(int area) override {if (area > 100) {homeBuyer.requestPurchase(area);} else {std::cout << "NO" << std::endl;}}
};int main() {HomePurchase* buyerProxy = new HomeAgentProxy();int n;std::cin >> n;for (int i = 0; i < n; ++i) {int area;std::cin >> area;buyerProxy->requestPurchase(area);}delete buyerProxy;return 0;
}

8 装饰模式

题目链接为：咖啡加糖

C++代码如下，

#include <iostream>
#include <memory>//咖啡接口
class Coffee {
public:virtual ~Coffee() {}virtual void brew() = 0;
};//具体的黑咖啡类
class BlackCoffee : public Coffee {
public:void brew() override {std::cout << "Brewing Black Coffee" << std::endl;}
};//具体的拿铁类
class Latte : public Coffee {
public:void brew() override {std::cout << "Brewing Latte" << std::endl;}
};//装饰者抽象类
class Decorator : public Coffee {
protected:std::unique_ptr<Coffee> coffee;public:Decorator(std::unique_ptr<Coffee> coffee) : coffee(std::move(coffee)) {}void brew() override {if (coffee) {coffee->brew();}}
};//具体的牛奶装饰者类
class MilkDecorator : public Decorator {
public:MilkDecorator(std::unique_ptr<Coffee> coffee) : Decorator(std::move(coffee)) {}void brew() override {Decorator::brew();std::cout << "Adding Milk" << std::endl;}
};//具体的糖类修饰者类
class SugarDecorator : public Decorator {
public:SugarDecorator(std::unique_ptr<Coffee> coffee) : Decorator(std::move(coffee)) {}void brew() override {Decorator::brew();std::cout << "Adding Sugar" << std::endl;}
};//客户端代码
int main() {int coffeeType, condimentType;while (std::cin >> coffeeType >> condimentType) {//根据输入制作咖啡std::unique_ptr<Coffee> coffee;if (coffeeType == 1) {coffee = std::make_unique<BlackCoffee>();} else if (coffeeType == 2) {coffee = std::make_unique<Latte>();} else {std::cout << "Invalid coffee type" << std::endl;continue;}//根据输入添加调料if (condimentType == 1) {coffee = std::make_unique<MilkDecorator>(std::move(coffee));} else if (condimentType == 2) {coffee = std::make_unique<SugarDecorator>(std::move(coffee));} else {std::cout << "Invalid condiment type" << std::endl;continue;}//输出制作过程coffee->brew();}return 0;
}