实验四

Task1:

GradeCalc.hpp

#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;
}

void GradeCalc::info()  {
    cout << "课程名称:\t" << course_name << endl;
    cout << "排序后成绩: \t";
    sort();  output();
    cout << "最高分:\t" << max() << endl;
    cout << "最低分:\t" << min() << endl;
    cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << endl;

    compute();  // 统计各分数段人数、比例

    vector<string> tmp{"[0, 60)  ", "[60, 70)", "[70, 80)","[80, 90)", "[90, 100]"};
    for(int i = tmp.size()-1; i >= 0; --i)
        cout << tmp[i] << "\t: " << counts[i] << "人\t"
             << std::fixed << std::setprecision(2) << rates[i]*100 << "%" << endl;
}

demo2.cpp

 

#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();
}

 

Q1、:在派生类 GradeCalc 中，成绩直接存储在基类 std::vector<int> 中。

方法 sort 使用 this->begin() 和 this->end() 迭代器访问成绩集合。

方法 min 和 max 调用了 std::min_element 和 std::max_element，同样通过迭代器访问成绩。

方法 average 利用 std::accumulate 遍历成绩集合。

方法 output 使用 this->begin() 和 this->end() 输出成绩。

方法 input 通过 this->push_back(grade) 将用户输入的每个成绩追加到 GradeCalc（即 std::vector<int>）中。

Q2、：功能是计算平均值

有影响，用来确保小数部分精度

Q3、：没有对成绩校验、只支持单一的成绩管理

 

Task2:

GradeCalc.hpp

#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;
}

void GradeCalc::info()  {
    cout << "课程名称:\t" << course_name << endl;
    cout << "排序后成绩: \t";
    sort();  output();
    cout << "最高分:\t" << max() << endl;
    cout << "最低分:\t" << min() << endl;
    cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << endl;

    compute();  // 统计各分数段人数、比例

    vector<string> tmp{"[0, 60)  ", "[60, 70)", "[70, 80)","[80, 90)", "[90, 100]"};
    for(int i = tmp.size()-1; i >= 0; --i)
        cout << tmp[i] << "\t: " << counts[i] << "人\t"
             << std::fixed << std::setprecision(2) << rates[i]*100 << "%" << endl;
}

demo3.cpp

#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();
}

 

问题：

 Q1、在 GradeCalc 类中，成绩存储在私有成员变量 grades 中

 

sort 使用了 grades.begin() 和 grades.end()，调用标准库的 std::sort 对成绩进行排序。

 

min 和 max 使用了 std::min_element 和 std::max_element，直接在 grades 容器范围内查找最小值和最大值。

 

average 使用了 std::accumulate 累加成绩总和，并通过班级人数计算平均分。

 

output 直接遍历 grades 容器，通过迭代输出每一个成绩。

与实验任务 2 的区别

成绩存储方式：实验任务 2 中的 GradeCalc 是继承自 std::vector<int>，成绩直接存储在父类 vector 中​(GradeCalc)。

访问方式差异：实验任务 2 的方法直接调用 this->begin() 等接口操作成绩，因为类本身就是一个 vector。

 

 Q2、

实验任务 2：直接继承 std::vector<int>，对外暴露了父类的所有接口（如 push_back 等），破坏了封装性。

实验任务 3：将成绩存储细节隐藏在私有变量 grades 中，通过类方法（如 input、output）控制数据访问，更符合封装原则。

 

Task3:

task4.1

#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();
}

 

 

 

作用是清除多余内容

task4.2

#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();
}

 

task4.3

#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();
}

 

 

 

作用是清空缓存的字符

Task5:

grm.hpp

#ifndef GRM_HPP
#define GRM_HPP

template<typename T>
class GameResourceManager {
private:
    T resource;
public:
    GameResourceManager(T initial) : resource(initial) {}

    T get() const {
        return resource;
    }

    void update(T change) {
        resource += change;
        if (resource < 0) {
            resource = 0;
        }
    }
};

#endif

task5.cpp

#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();
}

Task6:

info.hpp

#ifndef INFO_HPP
#define INFO_HPP

#include <iostream>
#include <string>
using std::string;
using std::cout;
using std::endl;

class Info {
private:
    string nickname;  // 昵称
    string contact;   // 联系方式（邮箱/手机号）
    string city;      // 所在城市
    int n;            // 预定参加人数

public:
    // 构造函数
    Info(const string& nickname, const string& contact, const string& city, int n)
        : nickname(nickname), contact(contact), city(city), n(n) {}

    // 获取预定人数
    int getN() const {
        return n;
    }

    // 更新预定人数
    void setN(int new_n) {
        n = new_n;
    }

    // 显示用户信息
    void display() const {
        cout << "昵称: " << nickname << endl;
        cout << "联系方式: " << contact << endl;
        cout << "所在城市: " << city << endl;
        cout << "预定人数: " << n << endl;
        cout << "--------------------" << endl;
    }
};

#endif // INFO_HPP

task6.cpp

#include "info.hpp"
#include <iostream>
#include <vector>
#include <string>
using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::vector;

int main() {
    const int capacity = 100;  // livehouse最大容量
    vector<Info> audience_lst; // 存储听众预约信息
    int total = 0;             // 当前总预约人数

    cout << "请输入听众预约信息:" << endl;

    while (true) {
        string nickname, contact, city;
        int n;

        cout << "昵称: ";
        cin >> nickname;
        cout << "联系方式: ";
        cin >> contact;
        cout << "所在城市: ";
        cin >> city;
        cout << "预定参加人数: ";
        cin >> n;

        // 检查剩余容量
        if (total + n > capacity) {
            cout << "对不起，场地仅剩 " << (capacity - total) << " 个位置。" << endl;
            cout << "1. 输入 u，更新(update)预定信息" << endl;
            cout << "2. 输入 q，退出预定" << endl;

            char choice;
            cin >> choice;

            if (choice == 'q') {
                continue; // 放弃当前用户
            } else if (choice == 'u') {
                cout << "请重新输入预定信息:" << endl;
                cout << "预定参加人数: ";
                cin >> n;
                if (n + total > capacity) {
                    cout << "仍超过剩余容量，预约失败。" << endl;
                    continue;
                }
            }
        }

        // 添加听众信息
        audience_lst.emplace_back(nickname, contact, city, n);
        total += n;

        // 检查是否达到容量上限
        if (total >= capacity) {
            cout << "预约已满，无法继续预约。" << endl;
            break;
        }

        // 停止录入（Ctrl+Z 或手动条件设计）
        cout << "是否继续录入？(Ctrl+Z停止)" << endl;
        if (cin.eof()) break;
    }

    // 输出听众预约信息
    cout << "截至目前，共有 " << total << " 位听众预约。预约听众信息如下:" << endl;
    cout << "--------------------" << endl;
    for (const auto& audience : audience_lst) {
        audience.display();
    }

    return 0;
}

 

 

Task7：

account.cpp

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

double Account::total = 0;

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::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::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());
}

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

void CreditAccount::settle(const Date& date) {
    double interest = acc.getSum(date) * rate;
    if (interest != 0) record(date, interest, "interest");
    if (date.getMonth() == 1) record(date, -fee, "annual fee");
    acc.reset(date, getDebt());
}

void CreditAccount::show() const {
    Account::show();
    cout << "\tAvailable credit: " << getAvailableCredit();
}

account.h

#pragma once
#ifndef ACCOUNT_H
#define ACCOUNT_H

#include "date.h"
#include "accumulator.h"
#include <string>

class Account {
private:
    std::string id;
    double balance;
    static double total;

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

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 getAvailableCredit() const {
        if (getBalance() < 0)
            return credit + getBalance();
        else
            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 // ACCOUNT_H

accumulator.h

#pragma once
#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 // ACCUMULATOR_H

date.cpp

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

namespace {
    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();
}

date.h

#ifndef __DATE_H__
#define __DATE_H__

class Date {
private:
    int year;
    int month;
    int day;
    int totalDays;

public:
    Date(int year, int month, int day);
    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;
    int distance(const Date& date) const {
        return totalDays - date.totalDays;
    }
};

#endif // __DATE_H__

task7.cpp

#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;
}