实验四

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 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;
}

task2.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 1：派生类 GradeCalc 定义中，成绩存储在继承自 vector<int>的对象中（即 this 所指向的对象）。派生类方法 sort、min、max、average、output 通过迭代器访问成绩，例如 begin () 和 end () 获取迭代器范围来遍历成绩。input 方法通过 push_back 接口实现数据存入对象。

问题 2：代码 line68 分母 n 的功能是计算成绩的平均值，用于将总成绩除以班级人数得到平均成绩。去掉乘以 1.0 代码，重新编译、运行，结果会有影响。因为 accumulate 函数返回的是整数类型的累加和，如果不乘以 1.0，在计算平均值时会进行整数除法，导致结果不准确，乘以 1.0 是为了将结果转换为浮点数，以得到正确的平均值。

问题 3：从真实应用场景角度考虑，GradeCalc 类在设计及代码实现细节上可能存在以下不足：没有考虑成绩录入的合法性检查，例如录入负数或大于 100 的数；对于大规模数据的排序效率可能较低，可考虑使用更高效的排序算法；没有提供修改成绩的功能；在分数段统计中，对于边界值的处理可能不够灵活，例如 60 分既属于 [0, 60) 又属于 [60, 70) 的情况没有明确规定；没有考虑多门课程成绩管理的情况，可进一步扩展为可以管理多门课程成绩的类1

task3

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;
    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;
}

task3.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1：存储在私有成员变量vector<int> grades；；通过直接访问grades

问题2：通过grades实现了更加方便的访问

task4

4.1.cpp

#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();
}

 

问题1：

忽略输入流cin中从当前位置开始直到下一个换行符（包括换行符本身）的所有字符 避免前一次输入的换行符或多余字符影响到下一次输入

4.2.cpp

#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.cpp

#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();
}

 忽略输入流中从当前位置开始直到下一个换行符（包括换行符本身）的所有字符

task5

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

#include <string>

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

public:
    Info(const std::string &nick, const std::string &cont, const std::string &cty, int num) :
    nickname(nick), contact(cont), city(cty), n(num) {}

    void display() const {
        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 << "预定人数: " << n << std::endl;
    }
};

task6.cpp

#include "info.hpp"
#include <iostream>
#include <vector>
#include <limits>

const int capacity = 100;

int main() {
    std::vector<Info> audience_list;
    int total = 0;
    while (true) {
        std::string nick, cont, city;
        int num;
        std::cout << "录入用户预约信息: " << std::endl;
        std::cout << "昵称 联系方式(邮箱/手机号) 所在城市 预定参加人数" << std::endl;
        if (!(std::cin >> nick >> cont >> city >> num)) {
            break;
        }
        if (total + num > capacity) {
            std::cout << "对不起,只剩 " << capacity - total << " 个位置. 输入u,更新(update)预定信息，输入q,退出预定" << std::endl;
            std::string choice;
            std::cin >> choice;
            if (choice == "u") {
                std::cout << "请重新输入预定信息: " << std::endl;
                continue;
            } else if (choice == "q") {
                break;
            }
        }
        audience_list.push_back(Info(nick, cont, city, num));
        total += num;
        if (total >= capacity) {
            std::cout << "截至目前,一共有 " << total << " 位听众预约。预约听众信息如下: " << std::endl;
            for (const auto &info : audience_list) {
                info.display();
            }
            break;
        }
    }
    return 0;
}

 

task7

account.h

#pragma once
#include"date.h"
#include"accumulator.h"
#include<string>
using namespace std;
class Account {
private:
    string id;
    double balance;
    static double total;
protected:
    Account(const Date& date, const string& id);
    void record(const Date& date, double amount, const string& desc);
    void error(const string& msg) const;
public:const string& getId() { 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 string& id, double rate);
    double getRate() const { return  rate; }
    void deposit(const Date& date, double amount, const string& desc);
    void withdraw(const Date& date, double amount, const 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 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 {
          if (getBalance() < 0)return credit + getBalance();
          else return credit;
      }
      void deposit(const Date& date, double amount, const string& desc);
      void withdraw(const Date& date, double amount, const string& desc);
      void settle(const Date& date);
      void show()const;
};

accumulator.h

#pragma once
#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;
        sum = 0;
    }
};

date.h

#pragma once
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;
    }
};

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 enouogh 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();
}

date.cpp

#pragma once
#include"date.h"
#include"accumulator.h"
#include<string>
using namespace std;
class Account {
private:
    string id;
    double balance;
    static double total;
protected:
    Account(const Date& date, const string& id);
    void record(const Date& date, double amount, const string& desc);
    void error(const string& msg) const;
public:const string& getId() { 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 string& id, double rate);
    double getRate() const { return  rate; }
    void deposit(const Date& date, double amount, const string& desc);
    void withdraw(const Date& date, double amount, const 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 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 {
          if (getBalance() < 0)return credit + getBalance();
          else return credit;
      }
      void deposit(const Date& date, double amount, const string& desc);
      void withdraw(const Date& date, double amount, const string& desc);
      void settle(const Date& date);
      void show()const;
};

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;

}