实验4

GradeCalc.h

#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
}

 

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();
}

问题一：std::string course_name;，保存课程名称

std::vector<int> grades;保存课程成绩列表

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 

问题二：不合法，input写成inupt了且push_back是vector的方法而不是GradeCalc的

问题三：一次，用来标记成绩信息是否有变来标记是否需要更新counts和rates

不需要，updata会改变is_dirty标记，触发compute函数

问题四：在info函数里面计算，先定义临时数组temp并复制数据，然后从小到大排序，并按照元素个数算出中位数

问题五：不能，每次改名或者使用compute函数都会导致counts和rates继承之前的数据导致数据错误

问题六：对功能没影响，对效率有影响，vector的频繁push_back会浪费大量时间，提前申请容量可以提高效率

 

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;
}

test2.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();
}

问题一：class GradeCalc: private std::vector<int> 

问题二：不会

不能通过编译，因为已private的权限继承的vector外部无法使用其接口

问题三：组合是通过对象的成员变量访问

继承是通过vector的基类接口访问数据

问题四：组合更适合因为在语义上是GradeCalc其中拥有vector成员，且vector本身已private继承接口隐藏，不如组合清晰

 

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();
}

 

问题一：std::vector<Graph*> graphs;   声明Graph类指针数组

class Circle : public Graph，class Triangle : public Graph，class Rectangle : public Graph

问题二：1：未声明为虚函数会导致始终调用基类的draw函数

2：push_back的数据是Graph*型，类型不匹配报错

3：只有基类的析构函数会被调用，导致内存泄漏

问题三：GraphType枚举列表内要添加星型

str_to_GraphType和make_graph中添加星型的对应分类

添加星型的类声明

问题四：1：会在~Canvas中被释放

2：可以自由分配和释放内存但是安全性差容易内存泄漏

 toy.hpp

#pragma once

#include <string>
#include <vector>

enum class ToyType {freddy,bonnie,chica,mangle};

class toy {
public:
    virtual void function() {}
    virtual void set() {}
    virtual void _printf() {}
    virtual ~toy() = default;
protected:
    std::string name;
    std::string type;
    std::string color;
};

class name1 : public toy {
private:
    void function();
    void set();
    void _printf();
};

class name2 : public toy {
private:
    void function();
    void set();
    void _printf();
};

class name3 : public toy {
private:
    void function();
    void set();
    void _printf();
};

class name4 : public toy {
private:
    void function();
    void set();
    void _printf();
};

class ToyFactory {
public:
    void add(const std::string& type); 
    void paint() const;     
    ~ToyFactory();         

private:
    std::vector<toy*> toys;          
};

// 4. 工具函数
ToyType str_to_ToyType(const std::string& s);  // 字符串转枚举类型
toy* make_toy(const std::string& type);  // 创建图形，返回堆对象指针

toy.cpp

#include <algorithm>
#include <cctype>
#include <iostream>
#include <string>

#include "toy.hpp"

void name1::set()
{
    name = "freddy";
    type = "bear";
    color = "brown";
}

void name2::set()
{
    name = "bonnie";
    type = "rabbit";
    color = "blue";
}

void name4::set()
{
    name = "mangle";
    type = "fox";
    color = "orange";
}

void name3::set()
{
    name = "chica";
    type = "chicken";
    color = "yellow";
}

void name1::_printf()
{
    std::cout << name << "\n" << type << "\n" << color << "\n";
}

void name2::_printf()
{
    std::cout << name << "\n" << type << "\n" << color << "\n";
}

void name3::_printf()
{
    std::cout << name << "\n" << type << "\n" << color << "\n";
}

void name4::_printf()
{
    std::cout << name << "\n" << type << "\n" << color << "\n";
}

void name1::function()
{
    std::cout << "Toy Freddy approaches from the main hallway. He blocks the flashlight, and you must use the Freddy mask to stop him.\n\n";
}


void name2::function()
{
    std::cout << "Toy Bonnie moves quickly and enters through the left vent. Putting on the Freddy mask immediately is the only way to avoid him.\n\n";
}

void name3::function()
{
    std::cout << "Toy Chica enters through the right vent. She becomes active early, and the player must use the Freddy mask to fool her.\n\n";
}

void name4::function()
{
    std::cout << "Mangle makes loud static noises and usually comes through the right vent. Once in the office, the mask won’t reliably stop it.\n\n";
}

ToyFactory::~ToyFactory() 
{
    for (toy* g : toys)
        delete g;
}

void ToyFactory::paint() const {
    for (toy* g : toys)
    {
        g->_printf();
        g->function();
    }
    
}

void ToyFactory::add(const std::string& type) {
    toy* g = make_toy(type);
    if (g) 
        toys.push_back(g);
    g->set();
}

// 工具函数实现
// 字符串 → 枚举转换
ToyType str_to_ToyType(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 == "freddy")   
        return ToyType::freddy;

    if (t == "bonnie") 
        return ToyType::bonnie;

    if (t == "chica")
        return ToyType::chica;

    if (t == "mangle")
        return ToyType::mangle;

    return ToyType::freddy;   // 缺省返回
}

// 创建图形，返回堆对象指针
toy* make_toy(const std::string& type) {
    switch (str_to_ToyType(type)) {
    case ToyType::freddy:     return new name1;
    case ToyType::bonnie:   return new name2;
    case ToyType::chica:  return new name3;
    case ToyType::mangle:  return new name4;
    default: return nullptr;
    }
}

demo4.cpp

#include <string>
#include "toy.hpp"

void test() {
    ToyFactory canvas;
    canvas.add("freddy");
    canvas.add("bonnie");
    canvas.add("chica");
    canvas.add("mangle");
    canvas.paint();
}

int main() {
    test();
}

toyfactory含一个toy基类数组，name继承了toy基类

只能输出已有信息不能输入