实验4 组合与继承
任务1：
GradeCalc.hpp
#pragma once #include <vector> #include <array> #include <string> class GradeCalc { public: GradeCalc(const std::string &cname); void input(int n); // 录入n个成绩 void output() const; // 输出成绩 void sort(bool ascending = false); // 排序 (默认降序) int min() const; // 返回最低分（如成绩未录入，返回-1) int max() const; // 返回最高分 （如成绩未录入，返回-1) double average() const; // 返回平均分 （如成绩未录入，返回0.0) void info(); // 输出课程成绩信息 private: void compute(); // 成绩统计 private: std::string course_name; // 课程名 std::vector<int> grades; // 课程成绩 std::array<int, 5> counts; // 保存各分数段人数（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100] std::array<double, 5> rates; // 保存各分数段人数占比 bool is_dirty; // 脏标记，记录是否成绩信息有变更 };
GradeCalc.cpp
#include <algorithm> #include <array> #include <cstdlib> #include <iomanip> #include <iostream> #include <numeric> #include <string> #include <vector> #include "GradeCalc.hpp" GradeCalc::GradeCalc(const std::string &cname):course_name{cname},is_dirty{true} { counts.fill(0); rates.fill(0); } void GradeCalc::input(int n) { if(n < 0) { std::cerr << "无效输入! 人数不能为负数\n"; std::exit(1); } grades.reserve(n); int grade; for(int i = 0; i < n;) { std::cin >> grade; if(grade < 0 || grade > 100) { std::cerr << "无效输入! 分数须在[0,100]\n"; continue; } grades.push_back(grade); ++i; } is_dirty = true; // 设置脏标记：成绩信息有变更 } void GradeCalc::output() const { for(auto grade: grades) std::cout << grade << ' '; std::cout << std::endl; } void GradeCalc::sort(bool ascending) { if(ascending) std::sort(grades.begin(), grades.end()); else std::sort(grades.begin(), grades.end(), std::greater<int>()); } int GradeCalc::min() const { if(grades.empty()) return -1; auto it = std::min_element(grades.begin(), grades.end()); return *it; } int GradeCalc::max() const { if(grades.empty()) return -1; auto it = std::max_element(grades.begin(), grades.end()); return *it; } double GradeCalc::average() const { if(grades.empty()) return 0.0; double avg = std::accumulate(grades.begin(), grades.end(), 0.0)/grades.size(); return avg; } void GradeCalc::info() { if(is_dirty) compute(); std::cout << "课程名称:\t" << course_name << std::endl; std::cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << std::endl; std::cout << "最高分:\t" << max() << std::endl; std::cout << "最低分:\t" << min() << std::endl; const std::array<std::string, 5> grade_range{"[0, 60) ", "[60, 70)", "[70, 80)", "[80, 90)", "[90, 100]"}; for(int i = static_cast<int>(grade_range.size())-1; i >= 0; --i) std::cout << grade_range[i] << "\t: " << counts[i] << "人\t" << std::fixed << std::setprecision(2) << rates[i]*100 << "%\n"; } void GradeCalc::compute() { if(grades.empty()) return; counts.fill(0); rates.fill(0.0); // 统计各分数段人数 for(auto grade:grades) { if(grade < 60) ++counts[0]; // [0, 60) else if (grade < 70) ++counts[1]; // [60, 70) else if (grade < 80) ++counts[2]; // [70, 80) else if (grade < 90) ++counts[3]; // [80, 90) else ++counts[4]; // [90, 100] } // 统计各分数段比例 for(size_t i = 0; i < rates.size(); ++i) rates[i] = counts[i] * 1.0 / grades.size(); is_dirty = false; // 更新脏标记 }
demo1.cpp
#include <iostream> #include <string> #include "GradeCalc.hpp" void test() { GradeCalc c1("OOP"); std::cout << "录入成绩:\n"; c1.input(5); std::cout << "输出成绩:\n"; c1.output(); std::cout << "排序后成绩:\n"; c1.sort(); c1.output(); std::cout << "*************成绩统计信息*************\n"; c1.info(); } int main() { test(); }
运行结果如图：
问题1：
std::vector<int>grades 存储学生成绩
std::array<int,5>couts 统计人数
std::array<double,5>rates 统计5个分段的百分比
问题2：不合法，grades是私有成员，无法通过push_back这个vector类的成员函数进行访问
问题3：（1）1次，避免重复使用
（2）不需要更改
问题4：在info里加入
int size = grades.size();
if (size % 2 == 1)
{ return grades[size / 2]; }
else
{ return (grades[size / 2 - 1] + grades[size / 2]) / 2.0; }
问题5：不能去掉，若去掉调用compute（）会将新的结果加到旧的结果上
问题6：（1）没有影响
（2）有影响，会导致内存不够
任务2：
GradeCalc.hpp
#pragma once #include <array> #include <string> #include <vector> class GradeCalc: private std::vector<int> { public: GradeCalc(const std::string &cname); void input(int n); // 录入n个成绩 void output() const; // 输出成绩 void sort(bool ascending = false); // 排序 (默认降序) int min() const; // 返回最低分 int max() const; // 返回最高分 double average() const; // 返回平均分 void info(); // 输出成绩统计信息 private: void compute(); // 计算成绩统计信息 private: std::string course_name; // 课程名 std::array<int, 5> counts; // 保存各分数段人数（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100] std::array<double, 5> rates; // 保存各分数段占比 bool is_dirty; // 脏标记，记录是否成绩信息有变更 };
GradeCalc.cpp
#include <algorithm> #include <array> #include <cstdlib> #include <iomanip> #include <iostream> #include <numeric> #include <string> #include <vector> #include "GradeCalc.hpp" GradeCalc::GradeCalc(const std::string &cname): course_name{cname}, is_dirty{true}{ counts.fill(0); rates.fill(0); } void GradeCalc::input(int n) { if(n < 0) { std::cerr << "无效输入! 人数不能为负数\n"; return; } this->reserve(n); int grade; for(int i = 0; i < n;) { std::cin >> grade; if(grade < 0 || grade > 100) { std::cerr << "无效输入! 分数须在[0,100]\n"; continue; } this->push_back(grade); ++i; } is_dirty = true; } void GradeCalc::output() const { for(auto grade: *this) std::cout << grade << ' '; std::cout << std::endl; } void GradeCalc::sort(bool ascending) { if(ascending) std::sort(this->begin(), this->end()); else std::sort(this->begin(), this->end(), std::greater<int>()); } int GradeCalc::min() const { if(this->empty()) return -1; return *std::min_element(this->begin(), this->end()); } int GradeCalc::max() const { if(this->empty()) return -1; return *std::max_element(this->begin(), this->end()); } double GradeCalc::average() const { if(this->empty()) return 0.0; double avg = std::accumulate(this->begin(), this->end(), 0.0) / this->size(); return avg; } void GradeCalc::info() { if(is_dirty) compute(); std::cout << "课程名称:\t" << course_name << std::endl; std::cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << std::endl; std::cout << "最高分:\t" << max() << std::endl; std::cout << "最低分:\t" << min() << std::endl; const std::array<std::string, 5> grade_range{"[0, 60) ", "[60, 70)", "[70, 80)", "[80, 90)", "[90, 100]"}; for(int i = static_cast<int>(grade_range.size())-1; i >= 0; --i) std::cout << grade_range[i] << "\t: " << counts[i] << "人\t" << std::fixed << std::setprecision(2) << rates[i]*100 << "%\n"; } void GradeCalc::compute() { if(this->empty()) return; counts.fill(0); rates.fill(0); // 统计各分数段人数 for(int grade: *this) { if(grade < 60) ++counts[0]; // [0, 60) else if (grade < 70) ++counts[1]; // [60, 70) else if (grade < 80) ++counts[2]; // [70, 80) else if (grade < 90) ++counts[3]; // [80, 90) else ++counts[4]; // [90, 100] } // 统计各分数段比例 for(size_t i = 0; i < rates.size(); ++i) rates[i] = counts[i] * 1.0 / this->size(); is_dirty = false; }
demo2.cpp
#include <iostream> #include <string> #include "GradeCalc.hpp" void test() { GradeCalc c1("OOP"); std::cout << "录入成绩:\n"; c1.input(5); std::cout << "输出成绩:\n"; c1.output(); std::cout << "排序后成绩:\n"; c1.sort(); c1.output(); std::cout << "*************成绩统计信息*************\n"; c1.info();
} int main() { test(); }
运行结果如下：
问题1：class GradeCalc : private std::vector<int>
问题2：基类`std::vector<int>`的接口不会自动成为`GradeCalc`的接口。
不能，push_back是公有接口，只能在继承类内部使用
问题3：组合方式通过公有接口访问，继承方式通过私有继承
问题4：组合方案更好
1.组合方案直接访问2.符合优先使用组合的原则
任务3：
Graph.hpp
#pragma once #include <string> #include <vector> enum class GraphType {circle, triangle, rectangle}; // Graph类定义 class Graph { public: virtual void draw() {} virtual ~Graph() = default; }; // Circle类声明 class Circle : public Graph { public: void draw(); }; // Triangle类声明 class Triangle : public Graph { public: void draw(); }; // Rectangle类声明 class Rectangle : public Graph { public: void draw(); }; // Canvas类声明 class Canvas { public: void add(const std::string& type); // 根据字符串添加图形 void paint() const; // 使用统一接口绘制所有图形 ~Canvas(); // 手动释放资源 private: std::vector<Graph*> graphs; }; // 4. 工具函数 GraphType str_to_GraphType(const std::string& s); // 字符串转枚举类型 Graph* make_graph(const std::string& type); // 创建图形，返回堆对象指针
Graph.cpp
#include <algorithm> #include <cctype> #include <iostream> #include <string> #include "Graph.hpp" // Circle类实现 void Circle::draw() { std::cout << "draw a circle...\n"; } // Triangle类实现 void Triangle::draw() { std::cout << "draw a triangle...\n"; } // Rectangle类实现 void Rectangle::draw() { std::cout << "draw a rectangle...\n"; } // Canvas类实现 void Canvas::add(const std::string& type) { Graph* g = make_graph(type); if (g) graphs.push_back(g); } void Canvas::paint() const { for (Graph* g : graphs) g->draw(); } Canvas::~Canvas() { for (Graph* g : graphs) delete g; } // 工具函数实现 // 字符串 → 枚举转换 GraphType str_to_GraphType(const std::string& s) { std::string t = s; std::transform(s.begin(), s.end(), t.begin(), [](unsigned char c) { return std::tolower(c);}); if (t == "circle") return GraphType::circle; if (t == "triangle") return GraphType::triangle; if (t == "rectangle") return GraphType::rectangle; return GraphType::circle; // 缺省返回 } // 创建图形，返回堆对象指针 Graph* make_graph(const std::string& type) { switch (str_to_GraphType(type)) { case GraphType::circle: return new Circle; case GraphType::triangle: return new Triangle; case GraphType::rectangle: return new Rectangle; default: return nullptr; } }
demo3.cpp
#include <string> #include "Graph.hpp" void test() { Canvas canvas; canvas.add("circle"); canvas.add("triangle"); canvas.add("rectangle"); canvas.paint(); } int main() { test(); }
运行结果如下：
问题1：（1）std::vector<Graph*>graphs;添加图形对象
（2）class Circle : public Graph{
public:
void draw();
};
class Triangle: public Graph{
public:
void draw();
};
class Rectangle: public Graph{
public:
void draw();
};
问题2：
（1）会导致无法指向对应的对象，无法输出有效对象
（2）无法使用Graph中子类的属性
（3）会导致派生类的析构函数无法被调用
问题3：
1. 在Graph.hpp中：
在`enum class GraphType`中添加`star`枚举值；
- 新增`Star`类的声明，使其继承自`Graph`。
2. 在Graph.cpp中：
- 实现`Star`类的`draw`函数；
- 在`str_to_GraphType`函数中添加对“star”字符串的处理；
- 在`make_graph`函数的switch语句中，添加`case GraphType::star`的分支，返回新的`Star`对象。
问题4：
1.在析构函数中被释放
2.会导致无法确定哪个指针指向不明
任务4：
toy.hpp
#ifndef TOY_HPP #define TOY_HPP #include <iostream> #include <string> class Toy { protected: std::string name; std::string type; std::string color; double batteryLevel; int productionYear; public: Toy(const std::string& name, const std::string& type, const std::string& color, int productionYear); virtual ~Toy(); virtual void specialFunction() const = 0; virtual void displayInfo() const; bool hasBattery() const; void chargeBattery(double amount); void useBattery(double amount); std::string getName() const { return name; } std::string getType() const { return type; } std::string getColor() const { return color; } double getBatteryLevel() const { return batteryLevel; } int getProductionYear() const { return productionYear; } int getAge(int currentYear) const; };
toy.cpp
#include "Toy.hpp" #include <iostream> Toy::Toy(const std::string& name, const std::string& type, const std::string& color, int productionYear) : name(name), type(type), color(color), batteryLevel(100.0), productionYear(productionYear) {} Toy::~Toy() { std::cout << "玩具 " << name << " 被销毁" << std::endl; } void Toy::displayInfo() const { std::cout << "═══════════════════════════════════════════" << std::endl; std::cout << "玩具名称: " << name << std::endl; std::cout << "玩具类型: " << type << std::endl; std::cout << "颜色: " << color << std::endl; std::cout << "生产年份: " << productionYear << std::endl; std::cout << "电池电量: " << batteryLevel << "%" << std::endl; } bool Toy::hasBattery() const { return batteryLevel > 0; } void Toy::chargeBattery(double amount) { if (amount > 0) { batteryLevel += amount; if (batteryLevel > 100.0) { batteryLevel = 100.0; } std::cout << name << " 充电完成，当前电量: " << batteryLevel << "%" << std::endl; } } void Toy::useBattery(double amount) { if (amount > 0) { batteryLevel -= amount; if (batteryLevel < 0) { batteryLevel = 0; } } } int Toy::getAge(int currentYear) const { return currentYear - productionYear; }
demo4.cpp
#include <iostream> #include "ToyFactory.hpp" #include "TalkingBear.hpp" #include "LightUpDog.hpp" #include "DancingRabbit.hpp" using namespace std; int main() { cout << "=== 毛绒玩具系统演示程序 ===" << endl; ToyFactory factory("我的玩具工厂"); vector<string> bearPhrases = {"你好！", "我爱玩！"}; TalkingBear* bear = new TalkingBear("小熊", "棕色", 2024, bearPhrases); LightUpDog* dog = new LightUpDog("小光", "白色", 2023, "蓝色"); vector<string> rabbitMoves = {"转圈", "跳跃"}; DancingRabbit* rabbit = new DancingRabbit("跳跳", "灰色", 2024, rabbitMoves); factory.addToy(bear); factory.addToy(dog); factory.addToy(rabbit); cout << "\n=== 显示所有玩具信息 ===" << endl; factory.showAllToys(); cout << "\n=== 演示特异功能 ===" << endl; factory.activateAllSpecialFunctions(); cout << "\n=== 工厂状态 ===" << endl; factory.showFactoryStatus(); cout << "\n=== 多态测试 ===" << endl; Toy* toys[] = {bear, dog, rabbit}; for (int i = 0; i < 3; i++) { cout << "\n玩具" << i+1 << ": "; toys[i]->specialFunction(); } cout << "\n=== 程序结束，自动清理 ===" << endl; return 0; }
运行结果如下：
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