实验4

#任务1

##代码

###GradeCalc.hpp

 1 #pragma once
 2 
 3 #include <vector>
 4 #include <array>
 5 #include <string>
 6 
 7 class GradeCalc {
 8 public:
 9     GradeCalc(const std::string &cname);      
10     void input(int n);                         // 录入n个成绩
11     void output() const;                      // 输出成绩
12     void sort(bool ascending = false);        // 排序 (默认降序)
13     int min() const;                          // 返回最低分（如成绩未录入，返回-1)
14     int max() const;                          // 返回最高分 （如成绩未录入，返回-1)
15     double average() const;                   // 返回平均分 （如成绩未录入，返回0.0)
16     void info();                      // 输出课程成绩信息 
17 
18 private:
19     void compute();     // 成绩统计
20 
21 private:
22     std::string course_name;     // 课程名
23     std::vector<int> grades;     // 课程成绩
24     std::array<int, 5> counts;      // 保存各分数段人数（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100]
25     std::array<double, 5> rates;    // 保存各分数段人数占比 
26     bool is_dirty;      // 脏标记，记录是否成绩信息有变更
27 };

###GradeCalc.cpp

  1 #include <algorithm>
  2 #include <array>
  3 #include <cstdlib>
  4 #include <iomanip>
  5 #include <iostream>
  6 #include <numeric>
  7 #include <string>
  8 #include <vector>
  9 
 10 #include "GradeCalc.hpp"
 11 
 12 GradeCalc::GradeCalc(const std::string &cname):course_name{cname},is_dirty{true} {
 13     counts.fill(0);
 14     rates.fill(0);   
 15 }
 16 
 17 void GradeCalc::input(int n) {
 18     if(n < 0) {
 19         std::cerr << "无效输入! 人数不能为负数\n";
 20         std::exit(1);
 21     }
 22 
 23     grades.reserve(n);
 24 
 25     int grade;
 26 
 27     for(int i = 0; i < n;) {
 28         std::cin >> grade;
 29 
 30         if(grade < 0 || grade > 100) {
 31             std::cerr << "无效输入! 分数须在[0,100]\n";
 32             continue;
 33         }
 34         
 35         grades.push_back(grade);
 36         ++i;
 37     }
 38 
 39     is_dirty = true;  // 设置脏标记：成绩信息有变更
 40 }
 41 
 42 void GradeCalc::output() const {
 43     for(auto grade: grades)
 44         std::cout << grade << ' ';
 45     std::cout << std::endl;
 46 }
 47     
 48 void GradeCalc::sort(bool ascending) {
 49     if(ascending)
 50         std::sort(grades.begin(), grades.end());
 51     else
 52         std::sort(grades.begin(), grades.end(), std::greater<int>());
 53 }
 54 
 55 int GradeCalc::min() const {
 56     if(grades.empty())
 57         return -1;
 58 
 59     auto it = std::min_element(grades.begin(), grades.end());
 60     return *it;
 61 }
 62 
 63 int GradeCalc::max() const {
 64     if(grades.empty()) 
 65         return -1;
 66 
 67     auto it = std::max_element(grades.begin(), grades.end());
 68     return *it;
 69 }
 70 
 71 double GradeCalc::average() const {
 72     if(grades.empty())
 73         return 0.0;
 74 
 75     double avg = std::accumulate(grades.begin(), grades.end(), 0.0)/grades.size();
 76     return avg;
 77 }
 78 
 79 void GradeCalc::info() {
 80     if(is_dirty) 
 81        compute();
 82 
 83     std::cout << "课程名称:\t" << course_name << std::endl;
 84     std::cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << std::endl;
 85     std::cout << "最高分:\t" << max() << std::endl;
 86     std::cout << "最低分:\t" << min() << std::endl;
 87 
 88     const std::array<std::string, 5> grade_range{"[0, 60) ", 
 89                                            "[60, 70)", 
 90                                            "[70, 80)",
 91                                            "[80, 90)", 
 92                                            "[90, 100]"};
 93     
 94     for(int i = static_cast<int>(grade_range.size())-1; i >= 0; --i)
 95         std::cout << grade_range[i] << "\t: " << counts[i] << "人\t"
 96                   << std::fixed << std::setprecision(2) << rates[i]*100 << "%\n";
 97 }
 98 
 99 void GradeCalc::compute() {
100     if(grades.empty())
101         return;
102 
103     counts.fill(0); 
104     rates.fill(0.0);
105 
106     // 统计各分数段人数
107     for(auto grade:grades) {
108         if(grade < 60)
109             ++counts[0];        // [0, 60)
110         else if (grade < 70)
111             ++counts[1];        // [60, 70)
112         else if (grade < 80)
113             ++counts[2];        // [70, 80)
114         else if (grade < 90)
115             ++counts[3];        // [80, 90)
116         else
117             ++counts[4];        // [90, 100]
118     }
119 
120     // 统计各分数段比例
121     for(size_t i = 0; i < rates.size(); ++i)
122         rates[i] = counts[i] * 1.0 / grades.size();
123     
124     is_dirty = false;  // 更新脏标记
125 }

###task1.cpp

 1 #include <iostream>
 2 #include <string>
 3 #include "GradeCalc.hpp"
 4 
 5 void test() {
 6     GradeCalc c1("OOP");
 7 
 8     std::cout << "录入成绩:\n";
 9     c1.input(5);
10 
11     std::cout << "输出成绩:\n";
12     c1.output();
13 
14     std::cout << "排序后成绩:\n";
15     c1.sort(); c1.output();
16 
17     std::cout << "*************成绩统计信息*************\n";
18     c1.info();
19 
20 
21 }
22 
23 int main() {
24     test();
25 }

##运行结果

image

 ##问题

###问题1

std::vector<int> grades;保存课程成绩

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

###问题2

不合法

push_back是vector<int> 的接口，组合类不允许使用其内部成员的接口

###问题3

只有第一次

控制compute()的调用，使得compute()只有在成绩被更新后才会在info中被使用

不需要更改 compute（）调用位置，但是需要在update_grade(index, new_grade)更新is_dirty的值

###问题4

在info中添加

sort();

std::cout << "中位数:\t" << (grades[grades.size()/2]+grades[(grades.size()-1)/2])/2<< std::endl;

###问题5

不行。

当数据变化后count中的数均不清零，会累积多次

###问题6

不受影响

更慢了

 

 

 

 

#任务2

##代码

###GradeCalc.hpp

 1 #pragma once
 2 
 3 #include <array>
 4 #include <string>
 5 #include <vector>
 6 
 7 class GradeCalc: private std::vector<int> {
 8 public:
 9     GradeCalc(const std::string &cname);      
10     void input(int n);                        // 录入n个成绩
11     void output() const;                      // 输出成绩
12     void sort(bool ascending = false);        // 排序 (默认降序)
13     int min() const;                          // 返回最低分
14     int max() const;                          // 返回最高分
15     double average() const;                   // 返回平均分
16     void info();                              // 输出成绩统计信息 
17 
18 private:
19     void compute();               // 计算成绩统计信息
20 
21 private:
22     std::string course_name;     // 课程名
23     std::array<int, 5> counts;   // 保存各分数段人数（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100]
24     std::array<double, 5> rates; // 保存各分数段占比
25     bool is_dirty;      // 脏标记，记录是否成绩信息有变更
26 };

###GradeCalc.cpp

  1 #include <algorithm>
  2 #include <array>
  3 #include <cstdlib>
  4 #include <iomanip>
  5 #include <iostream>
  6 #include <numeric>
  7 #include <string>
  8 #include <vector>
  9 #include "GradeCalc.hpp"
 10 
 11 
 12 GradeCalc::GradeCalc(const std::string &cname): course_name{cname}, is_dirty{true}{
 13     counts.fill(0);
 14     rates.fill(0);
 15 }   
 16 
 17 void GradeCalc::input(int n) {
 18     if(n < 0) {
 19         std::cerr << "无效输入! 人数不能为负数\n";
 20         return;
 21     }
 22 
 23     this->reserve(n);
 24 
 25     int grade;
 26 
 27     for(int i = 0; i < n;) {
 28         std::cin >> grade;
 29         if(grade < 0 || grade > 100) {
 30             std::cerr << "无效输入! 分数须在[0,100]\n";
 31             continue;
 32         }
 33 
 34         this->push_back(grade);
 35         ++i;
 36     } 
 37 
 38     is_dirty = true;
 39 }  
 40 
 41 void GradeCalc::output() const {
 42     for(auto grade: *this)
 43         std::cout << grade << ' ';
 44     std::cout << std::endl;
 45 } 
 46 
 47 void GradeCalc::sort(bool ascending) {
 48     if(ascending)
 49         std::sort(this->begin(), this->end());
 50     else
 51         std::sort(this->begin(), this->end(), std::greater<int>());
 52 }  
 53 
 54 int GradeCalc::min() const {
 55     if(this->empty())
 56         return -1;
 57 
 58     return *std::min_element(this->begin(), this->end());
 59 }  
 60 
 61 int GradeCalc::max() const {
 62     if(this->empty())
 63         return -1;
 64 
 65     return *std::max_element(this->begin(), this->end());
 66 }    
 67 
 68 double GradeCalc::average() const {
 69     if(this->empty())
 70         return 0.0;
 71 
 72     double avg = std::accumulate(this->begin(), this->end(), 0.0) / this->size();
 73     return avg;
 74 }   
 75 
 76 void GradeCalc::info() {
 77     if(is_dirty) 
 78         compute();
 79 
 80     std::cout << "课程名称:\t" << course_name << std::endl;
 81     std::cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << std::endl;
 82     std::cout << "最高分:\t" << max() << std::endl;
 83     std::cout << "最低分:\t" << min() << std::endl;
 84 
 85     const std::array<std::string, 5> grade_range{"[0, 60) ", 
 86                                            "[60, 70)", 
 87                                            "[70, 80)",
 88                                            "[80, 90)", 
 89                                            "[90, 100]"};
 90     
 91     for(int i = static_cast<int>(grade_range.size())-1; i >= 0; --i)
 92         std::cout << grade_range[i] << "\t: " << counts[i] << "人\t"
 93                   << std::fixed << std::setprecision(2) << rates[i]*100 << "%\n";
 94 }
 95 
 96 void GradeCalc::compute() {
 97     if(this->empty())
 98         return;
 99     
100     counts.fill(0);
101     rates.fill(0);
102 
103     // 统计各分数段人数
104     for(int grade: *this) {
105         if(grade < 60)
106             ++counts[0];        // [0, 60)
107         else if (grade < 70)
108             ++counts[1];        // [60, 70)
109         else if (grade < 80)
110             ++counts[2];        // [70, 80)
111         else if (grade < 90)
112             ++counts[3];        // [80, 90)
113         else
114             ++counts[4];        // [90, 100]
115     }
116 
117     // 统计各分数段比例
118     for(size_t i = 0; i < rates.size(); ++i)
119         rates[i] = counts[i] * 1.0 / this->size();
120     
121     is_dirty = false;
122 }

###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

image

##问题

###问题1

class GradeCalc: private std::vector<int>

###问题2

不会

不通过。私有继承

###问题3

前者是组合成员的接口，后者是自身继承的接口

###问题4

组合。封装性更合理

 

 

 

 

#任务3

##代码

###Graph.hpp

 1 #pragma once
 2 
 3 #include <string>
 4 #include <vector>
 5 
 6 enum class GraphType {circle, triangle, rectangle};
 7 
 8 // Graph类定义
 9 class Graph {
10 public:
11     virtual void draw() {}
12     virtual ~Graph() = default;
13 };
14 
15 // Circle类声明
16 class Circle : public Graph {
17 public:
18     void draw();
19 };
20 
21 // Triangle类声明
22 class Triangle : public Graph {
23 public:
24     void draw();
25 };
26 
27 // Rectangle类声明
28 class Rectangle : public Graph {
29 public:
30     void draw();
31 };
32 
33 // Canvas类声明
34 class Canvas {
35 public:
36     void add(const std::string& type);   // 根据字符串添加图形
37     void paint() const;                  // 使用统一接口绘制所有图形
38     ~Canvas();                           // 手动释放资源
39 
40 private:
41     std::vector<Graph*> graphs;          
42 };
43 
44 // 4. 工具函数
45 GraphType str_to_GraphType(const std::string& s);  // 字符串转枚举类型
46 Graph* make_graph(const std::string& type);  // 创建图形，返回堆对象指针

###Graph.cpp

 1 #include <algorithm>
 2 #include <cctype>
 3 #include <iostream>
 4 #include <string>
 5 
 6 #include "Graph.hpp"
 7 
 8 // Circle类实现
 9 void Circle::draw()     { std::cout << "draw a circle...\n"; }
10 
11 // Triangle类实现
12 void Triangle::draw()   { std::cout << "draw a triangle...\n"; }
13 
14 // Rectangle类实现
15 void Rectangle::draw()  { std::cout << "draw a rectangle...\n"; }
16 
17 // Canvas类实现
18 void Canvas::add(const std::string& type) {
19     Graph* g = make_graph(type);
20     if (g) 
21         graphs.push_back(g);
22 }
23 
24 void Canvas::paint() const {
25     for (Graph* g : graphs) 
26         g->draw();   
27 }
28 
29 Canvas::~Canvas() {
30     for (Graph* g : graphs) 
31         delete g;
32 }
33 
34 // 工具函数实现
35 // 字符串 → 枚举转换
36 GraphType str_to_GraphType(const std::string& s) {
37     std::string t = s;
38     std::transform(s.begin(), s.end(), t.begin(),
39                    [](unsigned char c) { return std::tolower(c);});
40 
41     if (t == "circle")   
42         return GraphType::circle;
43 
44     if (t == "triangle") 
45         return GraphType::triangle;
46 
47     if (t == "rectangle")
48         return GraphType::rectangle;
49 
50     return GraphType::circle;   // 缺省返回
51 }
52 
53 // 创建图形，返回堆对象指针
54 Graph* make_graph(const std::string& type) {
55     switch (str_to_GraphType(type)) {
56     case GraphType::circle:     return new Circle;
57     case GraphType::triangle:   return new Triangle;
58     case GraphType::rectangle:  return new Rectangle;
59     default: return nullptr;
60     }
61 }

###task3.cpp

 1 #include <string>
 2 #include "Graph.hpp"
 3 
 4 void test() {
 5     Canvas canvas;
 6 
 7     canvas.add("circle");
 8     canvas.add("triangle");
 9     canvas.add("rectangle");
10     canvas.paint();
11 }
12 
13 int main() {
14     test();
15 }

##运行结果

image

 ##问题

###问题1

(1)std::vector<Graph*> graphs　　储存不同的Graph类型的指针

(2)class Circle : public Graph；

class Triangle : public Graph；

class Rectangle : public Graph 

###问题2

运行基类Graph中的draw()

仅保留基类部分，丢失子类特性

仅调用基类析构函数，子类资源无法释放

###问题3

修改

enum class GraphType {circle, triangle, rectangle,star};

增加

class Star : public Graph {
public:
void draw();
};

增加

void Star::draw()  { std::cout << "draw a star...\n"; }

在GraphType str_to_GraphType中增加

if (t == "star")
return GraphType::star;

在Graph* make_graph中增加

case GraphType::star:     return new Star;

###问题4

(1)析构函数中

(2)优点是灵活可以直接修改内存，缺点是容易出现内存泄漏

 

 

 

#任务4

##代码

###Toy.hpp

 1 #pragma once
 2 
 3 #include <string>
 4 #include <vector>
 5 
 6 enum class GraphType {circle, triangle, rectangle};
 7 
 8 
 9 class Toy {
10     
11 
12 public:
13     Toy(std::string n, std::string t, std::string c);
14     std::string getName() const;
15     void show() const;
16     virtual void fun()=0;
17     virtual ~Toy() = default;
18     
19 protected:
20     std::string name;
21     std::string type;
22     std::string color; 
23     
24 };
25 
26 
27 class EleToy : public Toy {
28     
29 public:
30     EleToy(std::string n, std::string t, std::string c, int s);
31     void fun() ;
32     
33 private:
34     int btr;
35 };
36 
37 
38 class ToyFactory {
39 public:
40     void addToy(Toy* toy);  
41     void showToys() const;   
42     void tryfun() const;             
43     ~ToyFactory();                         
44 
45 private:
46     std::vector<Toy*> toyList;          
47 };

###Toy.cpp

 1 #include <algorithm>
 2 #include <cctype>
 3 #include <iostream>
 4 #include <string>
 5 
 6 #include "Toy.hpp"
 7 
 8 Toy::Toy(std::string n, std::string t, std::string c) : name{n}, type{t}, color{c}
 9 {}
10 void Toy::show() const
11 {
12     std::cout << "名称：" << name 
13               << ",类型：" << type 
14               << ",颜色：" << color << std::endl;
15 }
16 std::string Toy::getName() const
17 {
18     return name;
19 }
20 
21 EleToy::EleToy(std::string n, std::string t, std::string c, int s) : Toy(n, t, c), btr{s} 
22 {}
23 void EleToy::fun() {
24     if (btr >= 20)
25     {
26         std::cout << getName() << " 正常发光（当前电量：" << btr << "）" << std::endl;
27         btr -= 20; 
28     } 
29     else
30     {
31         std::cout << getName() << " 电量不足（当前电量：" << btr << "），无法启动功能！" << std::endl;
32     }
33 }
34 
35 
36 void ToyFactory::addToy(Toy* toy)
37 {
38     toyList.push_back(toy);
39 }
40 void ToyFactory::showToys() const
41 {
42     for (const auto& toy : toyList)
43     {
44         toy->show();
45     }
46 }
47 
48 void ToyFactory::tryfun() const
49 {
50     for (const auto& toy : toyList)
51     {
52         toy->fun();
53     }
54 }
55 ToyFactory::~ToyFactory() 
56 {
57     for (auto& toy : toyList)
58     {
59         delete toy;
60     }
61 }

###task4.cpp

 1 #include <string>
 2 #include "Toy.hpp"
 3 
 4 int main() {
 5    
 6     ToyFactory factory;
 7 
 8     factory.addToy(new EleToy("Pig", "坐垫", "white", 100));
 9     factory.addToy(new EleToy("Dog", "摆件", "green", 15));
10 
11   
12     factory.showToys();
13 
14  
15     factory.tryfun();
16 
17   
18     return 0;
19 }

##运行结果

image

 

posted @ 2025-12-03 00:14  五树  阅读(1)  评论(0)    收藏  举报