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实验4 类的组合、继承、模板类、标准库

任务一：

task1-1.cpp

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#include <iostream>

using std::cout;
using std::endl;

// 类A的定义
class A {
public:
    A(int x0, int y0);
    void display() const;

private:
    int x, y;
};

A::A(int x0, int y0): x{x0}, y{y0} {
}

void A::display() const {
    cout << x << ", " << y << endl;
}

// 类B的定义
class B {
public:
    B(double x0, double y0);
    void display() const;

private:
    double x, y;
};

B::B(double x0, double y0): x{x0}, y{y0} {
}

void B::display() const {
    cout << x << ", " << y << endl;
}

void test() {
    cout << "测试类A: " << endl;
    A a(3, 4);
    a.display();

    cout << "\n测试类B: " << endl;
    B b(3.2, 5.6);
    b.display();
}

int main() {
    test();
}
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task1-2.cpp

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#include <iostream>
#include <string>

using std::cout;
using std::endl;
using std::string;

// 定义类模板
template<typename T>
class X{
public:
    X(T x0, T y0);
    void display();

private:
    T x, y;
};

template<typename T>
X<T>::X(T x0, T y0): x{x0}, y{y0} {
}

template<typename T>
void X<T>::display() {
    cout << x << ", " << y << endl;
}


void test() {
    cout << "测试1: 类模板X中的抽象类型T用int实例化" << endl;
    X<int> x1(3, 4);
    x1.display();
    
    cout << endl;

    cout << "测试2: 类模板X中的抽象类型T用double实例化" << endl;
    X<double> x2(3.2, 5.6);
    x2.display();

    cout << endl;

    cout << "测试3: 类模板X中的抽象类型T用string实例化" << endl;
    X<string> x3("hello", "oop");
    x3.display();
}

int main() {
    test();
}
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task1-3.cpp

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#include <complex>
#include <vector>
#include <array>

int main() {
    using namespace std;
    
    complex<double> x1(5,3);        // complex类模板，特化到double类型
    vector<int> x2{1, 9, 8, 4};        // vector类模板，特化到int类型
    array<int, 4> x3{1,9, 8, 4};    // array类模板，特化到int类型
    // 其它略
}
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任务二：

GradeCalc.hpp

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#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iomanip>

using std::vector;
using std::string;
using std::cin;
using std::cout;
using std::endl;

class GradeCalc: public vector<int> {
public:
    GradeCalc(const string &cname, int size);      
    void input();                             // 录入成绩
    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
    float average() const;                    // 返回平均分
    void info();                              // 输出课程成绩信息 

private:
    void compute();     // 成绩统计

private:
    string course_name;     // 课程名
    int n;                  // 课程人数
    vector<int> counts = vector<int>(5, 0);      // 保存各分数段人数（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100]
    vector<double> rates = vector<double>(5, 0); // 保存各分数段比例 
};

GradeCalc::GradeCalc(const string &cname, int size): course_name{cname}, n{size} {}   

void GradeCalc::input() {
    int grade;

    for(int i = 0; i < n; ++i) {
        cin >> grade;
        this->push_back(grade);
    } 
}  

void GradeCalc::output() const {
    for(auto ptr = this->begin(); ptr != this->end(); ++ptr)
        cout << *ptr << " ";
    cout << 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 {
    return *std::min_element(this->begin(), this->end());
}  

int GradeCalc::max() const {
    return *std::max_element(this->begin(), this->end());
}    

float GradeCalc::average() const {
    return std::accumulate(this->begin(), this->end(), 0) * 1.0 / n;
}   

void GradeCalc::compute() {
    for(int grade: *this) {
        if(grade < 60)
            counts.at(0)++;
        else if(grade >= 60 && grade < 70)
            counts.at(1)++;
        else if(grade >= 70 && grade < 80)
            counts.at(2)++;
        else if(grade >= 80 && grade < 90)
            counts.at(3)++;
        else if(grade >= 90)
            counts.at(4)++;
    }

    for(int i = 0; i < rates.size(); ++i)
        rates.at(i) = counts.at(i) * 1.0 / n;
}
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task2.cpp

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#include "GradeCalc.hpp"
#include <iomanip>

void test() {
    int n;
    cout << "输入班级人数: ";
    cin >> n;

    GradeCalc c1("OOP", n);

    cout << "录入成绩: " << endl;;
    c1.input();
    cout << "输出成绩: " << endl;
    c1.output();

    cout << string(20, '*') + "课程成绩信息"  + string(20, '*') << endl;
    c1.info();
}

int main() {
    test();
}
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问题1：成绩存储在vector<int>中；

通过this->begin()和this->end()访问每个成绩；

通过this->push_back()实现；

问题2：计算平均值；有影响，*1.0可以将int型转换为浮点型，不加*1.0计算结果会舍去小数部分，计算结果不精确；

问题3：没有对输入的成绩进行合理性的判断。

任务三：

GradeCalc.hpp

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#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iomanip>

using std::vector;
using std::string;
using std::cin;
using std::cout;
using std::endl;

class GradeCalc {
public:
    GradeCalc(const string &cname, int size);      
    void input();                             // 录入成绩
    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
    float average() const;                    // 返回平均分
    void info();                              // 输出课程成绩信息 

private:
    void compute();     // 成绩统计

private:
    string course_name;     // 课程名
    int n;                  // 课程人数
    vector<int> grades;     // 课程成绩
    vector<int> counts = vector<int>(5, 0);      // 保存各分数段人数（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100]
    vector<double> rates = vector<double>(5, 0); // 保存各分数段比例 
};

GradeCalc::GradeCalc(const string &cname, int size): course_name{cname}, n{size} {}   

void GradeCalc::input() {
    int grade;

    for(int i = 0; i < n; ++i) {
        cin >> grade;
        grades.push_back(grade);
    } 
}  

void GradeCalc::output() const {
    for(int grade: grades)
        cout << grade << " ";
    cout << 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 {
    return *std::min_element(grades.begin(), grades.end());
}  

int GradeCalc::max() const {
    return *std::max_element(grades.begin(), grades.end());
}    

float GradeCalc::average() const {
    return std::accumulate(grades.begin(), grades.end(), 0) * 1.0 / n;
}   

void GradeCalc::compute() {
    for(int grade: grades) {
        if(grade < 60)
            counts.at(0)++;
        else if(grade >= 60 && grade < 70)
            counts.at(1)++;
        else if(grade >= 70 && grade < 80)
            counts.at(2)++;
        else if(grade >= 80 && grade < 90)
            counts.at(3)++;
        else if(grade >= 90)
            counts.at(4)++;
    }

    for(int i = 0; i < rates.size(); ++i)
        rates.at(i) = counts.at(i) *1.0 / n;
}
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task3.cpp

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#include "GradeCalc.hpp"
#include <iomanip>

void test() {
    int n;
    cout << "输入班级人数: ";
    cin >> n;

    GradeCalc c1("OOP", n);

    cout << "录入成绩: " << endl;;
    c1.input();
    cout << "输出成绩: " << endl;
    c1.output();

    cout << string(20, '*') + "课程成绩信息"  + string(20, '*') << endl;
    c1.info();
}

int main() {
    test();
}
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问题1：成绩存储在vector<int>grades中；通过grade.begin()和grade.end()访问。

问题2：两者的实现功能相同，但实现方式不同。任务二直接继承vector<int>，任务三则存储在私有成员grade，优化了代码。

任务四：

task4_1.cpp

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#include <iostream>
#include <string>
#include <limits>

using namespace std;

void test1() {
    string s1, s2;
    cin >> s1 >> s2;  // cin: 从输入流读取字符串, 碰到空白符(空格/回车/Tab)即结束
    cout << "s1: " << s1 << endl;
    cout << "s2: " << s2 << endl;
}

void test2() {
    string s1, s2;
    getline(cin, s1);  // getline(): 从输入流中提取字符串，直到遇到换行符
    getline(cin, s2);
    cout << "s1: " << s1 << endl;
    cout << "s2: " << s2 << endl;
}

void test3() {
    string s1, s2;
    getline(cin, s1, ' '); //从输入流中提取字符串，直到遇到指定分隔符
    getline(cin, s2);
    cout << "s1: " << s1 << endl;
    cout << "s2: " << s2 << endl;
}

int main() {
    cout << "测试1: 使用标准输入流对象cin输入字符串" << endl;
    test1();
    cout << endl;

    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    cout << "测试2: 使用函数getline()输入字符串" << endl;
    test2();
    cout << endl;

    cout << "测试3: 使用函数getline()输入字符串, 指定字符串分隔符" << endl;
    test3();
}
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问题1：

用于忽略输入过程中的某些操作符，如回车，避免对后续输入操作产生影响。

task4_2.cpp

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#include <iostream>
#include <string>
#include <vector>
#include <limits>

using namespace std;

void output(const vector<string> &v) {
    for(auto &s: v)
        cout << s << endl;
}

void test() {
    int n;
    while(cout << "Enter n: ", cin >> n) {
        vector<string> v1;

        for(int i = 0; i < n; ++i) {
            string s;
            cin >> s;
            v1.push_back(s);
        }

        cout << "output v1: " << endl;
        output(v1); 
        cout << endl;
    }
}

int main() {
    cout << "测试: 使用cin多组输入字符串" << endl;
    test();
}
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task4_3.cpp

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#include <iostream>
#include <string>
#include <vector>
#include <limits>

using namespace std;

void output(const vector<string> &v) {
    for(auto &s: v)
        cout << s << endl;
}

void test() {
    int n;
    while(cout << "Enter n: ", cin >> n) {
        cin.ignore(numeric_limits<streamsize>::max(), '\n');

        vector<string> v2;

        for(int i = 0; i < n; ++i) {
            string s;
            getline(cin, s);
            v2.push_back(s);
        }
        cout << "output v2: " << endl;
        output(v2); 
        cout << endl;
    }
}

int main() {
    cout << "测试: 使用函数getline()多组输入字符串" << endl;
    test();
}
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问题2：

用于忽略输入过程中操作符，避免对后续输入产生影响。

任务五：

grm.hpp:

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#ifndef GRM_HPP
#define GRM_HPP

template <typename T>
class GameResourceManager {
private:
    T resource;

public:
    GameResourceManager(T initial_value) : resource(initial_value) {}
    T get() const {
        return resource;
    }
    void update(T value) {
        resource += value;
        if (resource < 0) {
            resource = 0; 
        }
    }
};

#endif
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task5.cpp

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#include "grm.hpp"
#include <iostream>

using std::cout;
using std::endl;

void test1() {
    GameResourceManager<float> HP_manager(99.99);
    cout << "当前生命值: " << HP_manager.get() << endl;
    HP_manager.update(9.99);
    cout << "增加9.99生命值后, 当前生命值: " << HP_manager.get() << endl;
    HP_manager.update(-999.99);
    cout <<"减少999.99生命值后, 当前生命值: " << HP_manager.get() << endl;
}

void test2() {
    GameResourceManager<int> Gold_manager(100);
    cout << "当前金币数量: " << Gold_manager.get() << endl;
    Gold_manager.update(50);
    cout << "增加50个金币后, 当前金币数量: " << Gold_manager.get() << endl;
    Gold_manager.update(-99);
    cout <<"减少99个金币后, 当前金币数量: " << Gold_manager.get() << endl;
}


int main() {
    cout << "测试1: 用float类型对类模板GameResourceManager实例化" << endl;
    test1();
    cout << endl;

    cout << "测试2: 用int类型对类模板GameResourceManager实例化" << endl;
    test2();
}
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任务六：

 info.hpp

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#include <iostream>
#include <iomanip>
#include <string>

using std::string;

class Info {
private:
    string nickname;
    string contact;
    string city;
    int n;

public:
    Info(string nickname0, string contact0, string city0, int n0) : nickname(nickname0), contact(contact0), city(city0), n(n0) {}
    void display() {
        std::cout << "-------------------------------------------------" << std::endl;
        std::cout << "昵称: " << nickname << std::endl;
        std::cout << "联系方式: " << contact << std::endl;
        std::cout << "所在城市: " << city << std::endl;
        std::cout << "预定参加人数: " << n << std::endl;
    }
};
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task6.cpp

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#include<iostream>
#include<string>
#include<vector>
#include <iomanip>
#include"info.hpp"
  
using namespace std;
  
int main()
{
    const int capacity = 100;
    vector<Info> audience_lst;
    char choice;
    string nickname, contact, city;
    int n;
    cout << "录入用户预约信息：" << endl;
    cout << endl;
    cout << "昵称          "  << "联系方式(邮箱/手机号)          "  << "所在城市          "  << "预定参加人数          " << endl;
    int i = 0, sum = 0;
    while ((cin >> nickname >> contact >> city >> n))
    {
         
        audience_lst.push_back(Info(nickname, contact, city, n));
        sum += n;        
        i++;
           if (sum > capacity)
        {
               sum -= n;
            cout << "对不起，只剩" << capacity - sum << "个位置。\n";
            cout << "1.输入u,更新（update）预定信息\n";
            cout << "2.输入q,退出预定\n";
            cout << "你的选择：";             
            cin >> choice;
            if (choice == 'u')
             {
                cout << "请重新输入预定信息：\n";
                i--;
               audience_lst.pop_back();                    
               continue;
           }             
           else             
           {                 
                   break;
           }  
           }
    }
    cout << "截至目前，一共有" << sum << "位听众预约。预约听众信息如下：\n";
    for (int j = 0; j < i; j++)
    {
        audience_lst[j].display();
    }
}
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任务七：

date.h

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#ifndef __DATE_H__
#define __DATE_H__

class Date
{
private:
    int year;      // 年
    int month;     // 月
    int day;       // 日
    int totalDays; // 该日期是从公元元年1月1日开始的第几天
public:
    Date(int year, int month, int day); // 用年、月、日构造日期
    int getYear() const { return year; }
    int getMonth() const { return month; }
    int getDay() const { return day; }
    int getMaxDay() const;
    bool isLeapYear() const
    {
        return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
    }
    void show() const;
    // 计算两个日期之间相差多少天
    int distance(const Date &date) const
    {
        return totalDays - date.totalDays;
    }
};
#endif
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date.cpp

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#include "date.h"
#include <cstdlib>
#include <iostream>
using namespace std;

// 命名空间使下面的定义只在当前文件中有效
namespace
{
    // 存储平年中的某个月1日之前有多少天，为便于getMaxDay函数的实现，该数组多出一项
    const int DAYS_BEFORE_MONTH[] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365};
}

Date::Date(int year, int month, int day) : year(year), month(month), day(day)
{
    if (day <= 0 || day > getMaxDay())
    {
        cout << "Invalid date.";
        show();
        cout << endl;
        exit(1);
    }
    int years = year - 1;
    totalDays = years * 365 + years / 4 - years / 100 + years / 400 + DAYS_BEFORE_MONTH[month - 1] + day;
    if (isLeapYear() && month > 2)
        totalDays++;
}

int Date::getMaxDay() const
{
    if (isLeapYear() && month == 2)
    {
        return 29;
    }
    else
    {
        return DAYS_BEFORE_MONTH[month] - DAYS_BEFORE_MONTH[month - 1];
    }
}

void Date::show() const
{
    cout << getYear() << '-' << getMonth() << '-' << getDay();
}
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accumulator.h

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#ifndef _ACCUMULATOR_H_
#define _ACCUMULATOR_H_
#include "date.h"
class Accumulator {
private:
    Date lastDate;
    double value;
    double sum;
public:
    Accumulator(const Date& date, double value):lastDate(date),value(value),sum(0){ }
    double getSum(const Date& date) const {
        return sum + value * date.distance(lastDate);
    }
    void change(const Date& date, double value) {
        sum = getSum(date);
        lastDate = date;
        this->value = value;
    }
    void reset(const Date& date, double value) {
        lastDate = date;
        this->value = value;
        sum = 0;
    }
};
#endif
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account.h

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#ifndef _ACCOUNT_H_
#define _ACCOUNT_H_
#include "accumulator.h"
#include "date.h"
#include <string>
class Account
{
private:
    std::string id;
    double balance;
    static double total;

protected:
    Account(const Date &date, const std::string &id);
    void error(const std::string &msg) const;
    void record(const Date &data, double amount, const std::string &desc);

public:
    const std::string &getId() const { return id; }
    double getBalance() const { return balance; }
    static double getTotal() { return total; }
    void show() const;
};
class SavingsAccount : public Account
{
private:
    Accumulator acc;
    double rate;

public:
    SavingsAccount(const Date &date, const std::string &id, double rate);
    double getRate() const { return rate; }
    void deposit(const Date &date, double amount, const std::string &desc);
    void withdraw(const Date &date, double amount, const std::string &desc);
    void settle(const Date &date);
};
class CreditAccount : public Account
{
private:
    Accumulator acc;
    double credit;
    double rate;
    double fee;
    double getDebt() const
    {
        double balance = getBalance();
        return (balance < 0 ? balance : 0);
    }

public:
    CreditAccount(const Date &date, const std::string &id, double credit, double rate, double fee);
    double getCredit() const { return credit; }
    double getRate() const { return rate; }
    double getFee() const { return fee; }
    double getAvailableCredit() const { return credit; }
    void deposit(const Date &date, double amount, const std::string &desc);
    void withdraw(const Date &date, double amount, const std::string &desc);
    void settle(const Date &date);
    void show() const;
};
#endif
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account.cpp

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#include "account.h"
#include <cmath>
#include <iostream>
using namespace std;
double Account::total = 0;

// Account类的实现
Account::Account(const Date &date, const string &id) : id(id), balance(0)
{
    date.show();
    cout << "\t#" << id << " created" << endl;
}

void Account::record(const Date &date, double amount, const string &desc)
{
    amount = floor(amount * 100 + 0.5) / 100;
    balance += amount;
    total += amount;
    date.show();
    cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl;
}

void Account::show() const
{
    cout << id << "\tBalance: " << balance;
}

void Account::error(const string &msg) const
{
    cout << "Error(#" << id << "): " << msg << endl;
}

// SavingsAccount类相关成员函数的实现
SavingsAccount::SavingsAccount(const Date &date, const string &id, double rate) : Account(date, id), rate(rate), acc(date, 0) {}

void SavingsAccount::deposit(const Date &date, double amount, const string &desc)
{
    record(date, amount, desc);
    acc.change(date, getBalance());
}

void SavingsAccount::withdraw(const Date &date, double amount, const string &desc)
{
    if (amount > getBalance())
    {
        error("not enough money");
    }
    else
    {
        record(date, -amount, desc);
        acc.change(date, getBalance());
    }
}

void SavingsAccount::settle(const Date &date)
{
    double interest = acc.getSum(date) * rate / date.distance(Date(date.getYear() - 1, 1, 1));
    if (interest != 0)
        record(date, interest, "interest");
    acc.reset(date, getBalance());
}

// CreditAccount类相关成员函数的实现
CreditAccount::CreditAccount(const Date &date, const string &id, double credit, double rate, double fee) : Account(date, id), credit(credit), rate(rate), fee(fee), acc(date, 0) {}

void CreditAccount::deposit(const Date &date, double amount, const string &desc)
{
    record(date, amount, desc);
    acc.change(date, getDebt());
}
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task7.cpp

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#include "account.h"
#include <iostream>
using namespace std;

int main()
{
    Date date(2008, 11, 1);

    SavingsAccount sa1(date, "S3755217", 0.015);
    SavingsAccount sa2(date, "02342342", 0.015);
    CreditAccount ca(date, "C5392394", 10000, 0.0005, 50);

    sa1.deposit(Date(2008, 11, 5), 5000, "salary");
    ca.withdraw(Date(2008, 11, 15), 2000, "buy a cell");
    sa2.deposit(Date(2008, 11, 25), 10000, "sell stock 0323");

    ca.settle(Date(2008, 12, 1));

    ca.deposit(Date(2008, 12, 1), 2016, "repay the credit");
    sa1.deposit(Date(2008, 12, 5), 5500, "salary");

    sa1.settle(Date(2009, 1, 1));
    sa2.settle(Date(2009, 1, 1));
    ca.settle(Date(2009, 1, 1));

    cout << endl;
    sa1.show();
    cout << endl;
    sa2.show();
    cout << endl;
    ca.show();
    cout << endl;
    cout << "Total: " << Account::getTotal() << endl;
    return 0;
}
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