实验4

实验4 类的组合、继承、模板类、标准库

实验任务1 ：自行练习

实验任务2

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，成绩存储在哪里？派生类方法sort, min, max, average,

output都要访问成绩，是通过什么接口访问到每个成绩的？input方法是通过什么接口实现数

据存入对象的？

成绩储存在vector<int>的grade中；通过this指针接口访问到每个成绩；input通过push_back函数接口实现存入数据

问题2：

代码line68分母的功能是？去掉乘以1.0代码，重新编译、运行，结果有影响吗？为什么要乘以1.0？

计算平均值；去掉的话结果是向下取整后的；*1.0后变成double类型

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，有哪些地方尚未

考虑周全，仍需继续迭代、完善？

需要判空

实验任务3

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;
}

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：

组合类GradeCalc定义中，成绩存储在哪里？组合类方法sort, min, max, average,

output都要访问成绩，是通过什么接口访问到每个成绩的？观察与实验任务2在代码写法细节

上的差别。

成绩存储在vector<int>的grades里；通过迭代器grades.begin(),grades.end()来排序，for循环访问成绩并输出;实验二使用的是this指针.

问题2：

对比实验任务2和实验任务3，主体代码逻辑（测试代码）没有变更，类GradeCalc的

接口也没变，变化的是类GradeCalc的设计及接口内部实现细节。你对面向对象编程有什么新

的理解和领悟吗？

面向对象编程实现的方法多样，在类的逻辑、接口没有变化的基础上，可以通过对内部细节的变化实现分装以及继承。

实验任务4

task4_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：

去掉task4_1.cpp的line35，重新编译、运行，给出此时运行结果截图。查阅资料，回答

line35在这里的用途是什么？

“吃掉”一个"\n"；

task4_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();
}

问题2：

问题2：去掉task4_3.cpp的line16，重新编译、运行，给出此时运行结果。查阅资料，回答line16

在这里的用途是什么？

“吃掉”一个"\n"；

实验任务5

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();
}

grm.hpp

#include <bits/stdc++.h>
using namespace std;

template<typename T>
class GameResourceManager{
public:
    GameResourceManager(T x0);
    T get() const;
    void update(T num);
private:
    T x;
};

template<typename T>
GameResourceManager<T>::GameResourceManager(T x0):x(x0){};

template<typename T>
T GameResourceManager<T>::get() const
{
    return x;
}

template<typename T>
void GameResourceManager<T>::update(T num)
{
    x+=num;
    if (x<0) x=0;
}

实验任务6

Info.hpp

#include <bits/stdc++.h>
using namespace std;

class Info{
private:
    string nickname;
    string contact;
    string city;
    int n;
public:
    Info(string nickname,string contact,string city,int n);
    void display() const;
};

Info::Info(string name,string con,string c,int n1)
{
    nickname=name;
    contact=con;
    city=c;
    n=n1;
}
void Info::display() const
{
    cout<<setw(20)<<left<<"昵称:"<<nickname<<endl;
    cout<<setw(20)<<left<<"联系方式:"<<contact<<endl;
    cout<<setw(20)<<left<<"所在城市:"<<city<<endl;
    cout<<setw(20)<<left<<"预定人数:"<<n<<endl;
}

//A.cpp
#include "Info.hpp"
#include <bits/stdc++.h>
using namespace std;

const int capacity=100;

int main ()
{
    vector<Info> audience_lst;
    cout<<"录入用户预约信息:"<<endl<<endl;
    cout<<setw(10)<<left<<"昵称";
    cout<<setw(30)<<left<<"联系方式(邮箱/手机号)";
    cout<<setw(20)<<left<<"所在城市";
    cout<<setw(10)<<left<<"预定参加人数"<<endl;
    int now_capacity=0;
    string nickname,contact,city;
    int n;
    while(now_capacity<capacity && cin>>nickname>>contact>>city>>n)
    {
        now_capacity+=n;
        if (now_capacity<=capacity)
        {
            audience_lst.push_back(Info(nickname,contact,city,n));
        }
        else
        {
            now_capacity-=n;
            cout<<"对不起,只剩80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:";
            char choose;
            cin>>choose;
            if (choose=='u')
            {
                cout<<"请重新输入预定信息:"<<endl;
                continue;
            }
            else if(choose=='q')
            {
                break;
            }
        }
    }
    cout<<"截至目前，一共有"<<now_capacity<<"为听众预约。预约听众信息如下:"<<endl; 
    int len=audience_lst.size();
    for (int i=0;i<len;i++)
    {
        cout<<string(50,'-')<<endl;
        audience_lst[i].display();
    }
    return 0;
}

实验任务7

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();
}

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();
}

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

A.cpp

 #include"account.cpp"
#include"date.cpp"
#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;
}

1.增加了储蓄账户类的派生类信用账户类（公有继承），完善了银行储蓄账户的种类，更加符合生活实际

2.不同派生类的函数相互独立，只有知道对象的具体类型后才能调用