实验4

task1

#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();
}

　　

#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();
}

　　

 task2

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();
}

　　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; 
} 

　　

问题1：

成绩存储在当前类继承的std::vector<int>容器中。min、sort、max、average、output是通过std::vector的公共接口访问成绩数据的，input 通过std::vector中的push_back成员函数将用户的数据存储到类中。

问题2：

代码的功能是求平均值。去掉1.0后平均分变为78.00。称于1.0是为了确保浮点数除法，防止精度丢失。

task3

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();
}

　　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; 
} 

　　

问题1：

 成绩存储在std::vector<int>这个容器中。min、max、sort、average、output是通过std::vector<int>提供的迭代器接口访问每个成绩。实验2是基于继承的方式操作std::vector<int>中的一些函数,实验3则是以组合的方式来操作std::vector<int>中的一些函数；实验2中一些函数的调用是以“this->(函数）”的操作，而实验3则是“grades.(函数）”的方式。

问题2：

在处理问题时，我们要选择合理的方式来进行类间的相互调用。有继承，包含。继承减少了内存，包含可更好的增加代码封装性。

task4

#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();
}

　　

#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();
}

　　

 

#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();
}

　　

问题：

 

cin.ignore(numeric_limits<streamsize>::max(), '\n')的作用时清除输入缓冲区剩余的字符，直至遇到'\n'。

输入缓冲区（Input Buffer）：当用户通过键盘输入数据时，数据首先存储在输入缓冲区中。程序通过输入流（如 cin）从缓冲区中读取数据。
换行符（'\n'）：当用户按下回车键时，换行符会被添加到输入缓冲区的末尾，表示输入的结束。

在运行test1时，缓冲区会留下一个换行符‘\n’，test2s1会读取换行符，导致s1为空字符串，而getline会读入换行符。

 getline(cin, s1, ' '); //从输入流中提取字符串，直到遇到指定分隔符,默认是换行符。

 task5

grm.hpp

#include <iostream>

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

template <typename ElemType>
class GameResourceManager
{
public:
    GameResourceManager(ElemType a) :resource{a} {};
    ElemType get()
    {
        return resource;
    }
    void update(int t)
    {
        resource += t;
        if (resource < 0)resource = 0;
    }
private:
    ElemType resource;
};

　　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.cpp

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

using namespace std;

class info
{
public:
    info(string ni, string con, string ci, int n) :nickname{ni}, contact{con}, city{ci}, n{n} {}
    void display()
    {
        cout << "呢称：             " << 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;
    }
private:
    string nickname, contact, city;
    int n;
};

　　task6.cpp

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

using namespace std;
const int capacity = 100;

int main()
{
    int n, sum = 0;
    string name, email, city;
    char choose;
    vector<info> audience_lst;
    cout << "录入用户预约信息：" << endl;
    cout << "呢称           " << "联系方式（邮箱／手机号）       " << "所在城市         " << "预定参加人数       " << endl;
    while (cin >> name >> email >> city >> n) {
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
        if (sum + n > capacity) {
            cout << "对不起，只剩" << capacity - sum << "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;
            cout << "你的选择：", cin >> choose;
            if (choose == 'u') {
                cin.ignore(numeric_limits<streamsize>::max(), '\n');
                cout << "请重新输入预定信息：" << endl;
                cin >> name >> email >> city >> n;
                info t(name, email, city, n);
                audience_lst.push_back(t);
                sum += n;
                break;
            }
            else if (choose == 'q')break;
        }
        info t(name, email, city, n);
        audience_lst.push_back(t);
        sum += n;
    }
    cout << "截至目前，一共有" << sum << "位听众预约。预约听众信息如下：" << endl;
    cout << "---------------------------------------------------" << endl;
    for (auto& s : audience_lst)
    {
        s.display();
    }
}

　　

 

 task7

date.h

#pragma once
#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

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();
}

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

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

　　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();
}

task6.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;
}