实验4
实验任务1
源代码：
GradeCalc.hpp:
#pragma once #include <vector> #include <array> #include <string> class GradeCalc { public: GradeCalc(const std::string &cname); void input(int n); void output() const; void sort(bool ascending = false); int min() const; int max() const; double average() const; void info(); private: void compute(); private: std::string course_name; std::vector<int> grades; std::array<int, 5> counts; std::array<double, 5> rates; bool is_dirty; };
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; } 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); for(auto grade:grades) { if(grade < 60) ++counts[0]; else if (grade < 70) ++counts[1]; else if (grade < 80) ++counts[2]; else if (grade < 90) ++counts[3]; else ++counts[4]; } for(size_t i = 0; i < rates.size(); ++i) rates[i] = counts[i] * 1.0 / grades.size(); is_dirty = false; }
task1.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(); }
运行结果截图：
问题1：
std::string course_name;功能是存储课程名
std::vector<int> grades;功能是存储课程成绩
std::array<int, 5> counts;功能是保存各分数段人数
std::array<double, 5> rates;功能是保存各分数段人数占比
bool is_dirty;功能是记录是否成绩信息有变更
问题2：
不合法，push_back()是vector里的成员函数，而vector的对象grades是类里的私有成员，外部不能用
问题3：
（1）compute调用1次，因为成绩信息未改变，if_dirty用于记录成绩信息是否有变更
（2）不需要，只要info函数中检测到if_dirty为true,则会调用compute
问题4：
{
if(grades.size()==1{
return grades[grades.size()/2];
{
else{
return (grades[grades.size()/2]+grades[grades.size()/2-1])/2;
}
}在info函数里加
问题5：
不能去掉，在进行多次成绩存储时会出现错误
问题6：
（1）对功能无影响，去掉后仍能运行
（2）对性能有影响，存储空间不足是会重新分配新内存，运行影响效率
实验任务2：
源代码：
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); void output() const; void sort(bool ascending = false); int min() const; int max() const; double average() const; void info(); private: void compute(); private: std::string course_name; std::array<int, 5> counts; std::array<double, 5> rates; bool is_dirty; };
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); for(int grade: *this) { if(grade < 60) ++counts[0]; else if (grade < 70) ++counts[1]; else if (grade < 80) ++counts[2]; else if (grade < 90) ++counts[3]; else ++counts[4]; } for(size_t i = 0; i < rates.size(); ++i) rates[i] = counts[i] * 1.0 / this->size(); is_dirty = false; }
task2.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(); }
运行结果截图：
问题1：
class GradeCalc: private std::vector<int>{
问题2：
基类vector<int>的接口不会自动成为GradeCalc的接口
编译不能通过，因为是私有继承，所以push_back()不能在外部被访问
问题3：
组合方式通过grades接口访问数据
继承方式通过this访问数据
问题4：
组合方案更适合，组合的封装性更强，安全性高，且组合灵活性好，方便后续功能添加修改
实验任务3
源代码：
Graph.hpp:
#pragma once #include <string> #include <vector> enum class GraphType {circle, triangle, rectangle}; class Graph { public: virtual void draw() {} virtual ~Graph() = default; }; class Circle : public Graph { public: void draw(); }; class Triangle : public Graph { public: void draw(); }; class Rectangle : public Graph { public: void draw(); }; class Canvas { public: void add(const std::string& type); void paint() const; ~Canvas(); private: std::vector<Graph*> graphs; }; GraphType str_to_GraphType(const std::string& s); Graph* make_graph(const std::string& type);
Graph.cpp:
#include <algorithm> #include <cctype> #include <iostream> #include <string> #include "Graph.hpp" void Circle::draw() { std::cout << "draw a circle...\n"; } void Triangle::draw() { std::cout << "draw a triangle...\n"; } void Rectangle::draw() { std::cout << "draw a rectangle...\n"; } 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; } 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; } 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; } }
task3.cpp:
#include <string> #include "Graph.hpp" void test() { Canvas canvas; canvas.add("circle"); canvas.add("triangle"); canvas.add("rectangle"); canvas.paint(); } int main() { test(); }
运行结果截图：
问题1：
（1）std::vector<Graph*> graphs;功能是存储图的指针
（2）class Circle : public Graph {
class Triangle : public Graph {
class Rectangle : public Graph {
问题2：
（1）会调用基类的draw而非子类的，没有输出
（2）调用draw()时只会执行基类的函数draw()，而不会执行子类的
（3）会导致子类折构不能进行
问题3：
Garph.hpp中声明Star类，枚举中增加star
Graph.cpp中增加Star::draw的实现，工具函数里也增加star对应的内容
task4.cpp中的test函数里增加canvas.add("star");
问题4：
（1）在析构函数中被释放
（2）利：简单，灵活性高
弊：需要手动分配内存
实验任务4
源代码：
Toy.hpp:
#pragma once #include <iostream> #include <string> #include <vector> class Toy { public: Toy(std::string n,std::string t,std::string p,std::string c); void output(); virtual void specialfunction(); virtual ~Toy(); private: std::string name; std::string type; std::string price; std::string color; }; class BrightToy:public Toy{ public: BrightToy(std::string n,std::string t,std::string p,std::string c,std::string b); void specialfunction(); private: std::string brightcolor; }; class SoundToy:public Toy{ public: SoundToy(std::string n,std::string t,std::string p,std::string c,std::string s); void specialfunction(); private: std::string soundtype; }; class MoveToy:public Toy{ public: MoveToy(std::string n,std::string t,std::string p,std::string c,std::string m); void specialfunction(); private: std::string movetype; }; class ToyFactory{ public: ToyFactory(std::string n); void addToy(Toy* toy); void TFoutput(); ~ToyFactory(); private: std::string factoryname; std::vector<Toy*> toys; };
Toy.cpp:
#include "Toy.hpp" Toy::Toy(std::string n,std::string t,std::string p,std::string c):name(n),type(t),price(p),color(c){} void Toy::output(){ std::cout<<"名称："<<name<<"\n种类："<<type<<"\n颜色："<<color<<"\n价格："<<price<<std::endl; } Toy::~Toy(){} void Toy::specialfunction(){ output(); } BrightToy::BrightToy(std::string n,std::string t,std::string p,std::string c,std::string b):Toy(n,t,p,c),brightcolor(b){} void BrightToy::specialfunction(){ output(); std::cout<<"特异功能：发出" <<brightcolor<<"的光"<<std::endl; std::cout<<std::endl; } SoundToy::SoundToy(std::string n,std::string t,std::string p,std::string c,std::string s):Toy(n,t,p,c),soundtype(s){} void SoundToy::specialfunction(){ output(); std::cout<<"特异功能：发出" <<soundtype<<"的声音"<<std::endl; std::cout<<std::endl; } MoveToy::MoveToy(std::string n,std::string t,std::string p,std::string c,std::string m):Toy(n,t,p,c),movetype(m){} void MoveToy::specialfunction(){ output(); std::cout<<"特异功能：做出" <<movetype<<"的动作"<<std::endl; std::cout<<std::endl; } ToyFactory::ToyFactory(std::string n):factoryname(n){} void ToyFactory::addToy(Toy* toy){ if(toy!=nullptr){ toys.push_back(toy); } } void ToyFactory::TFoutput(){ std::cout<<"************"<<factoryname<<"玩具信息************"<<std::endl; for(auto& toy:toys){ toy->specialfunction(); } } ToyFactory::~ToyFactory(){ for(auto toy:toys){ delete toy; } }
task4.cpp:
#include "Toy.hpp" void test(){ ToyFactory factory("南京玩具工厂"); factory.addToy(new BrightToy("小猫","发光玩具","黄色","50元","白色")); factory.addToy(new SoundToy("鹦鹉","声音模仿玩具","红色","80元","小狗")); factory.addToy(new MoveToy("兔子","运动玩具","白色","90元","跳跃")); factory.addToy(new BrightToy("小狗","发光玩具","棕色","60元","黄色")); factory.TFoutput(); } int main(){ test(); return 0; }
运行结果截图：
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