一、实验目的
- 知道什么是类模板，会正确定义和使用简单的类模板
- 会使用C++正确定义、使用派生类
- 加深对类的组合机制(has-a)、类的继承机制(is-a)的领悟和理解
- 练习标准库string, vector用法，能基于问题场景灵活使用
- 针对具体问题场景，练习运用面向对象思维进行设计，组合使用标准库和自定义类，编程解决实际问题
二、实验内容
1. 实验任务1
task1_1.cpp#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();
}
运行结果：
task1_2.cpp
#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();
}
运行结果：
2. 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();
}
运行结果：
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？ 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？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？
答：1. GradeCalc类继承于vector类，而成绩数据则存储在vector容器中；通过继承而来的begin()和end()访问到每个成绩；input通过继承来的push_back()实现数据存入对象。
2. 分母的作用是除以总数以获取平均值，有影响，乘1.0是将值的类型强制转换为浮点数，以便平均值计算的准确性。
3. 没有对成绩的输入进行合法性查验。
3. 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();
}
运行结果：
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。 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？答：1.成绩储存在GradeCalc类中的一个vector类型的私有成员变量grades中；
通过直接访问grades对象来访问每个成绩。
2.在面向对象编程的过程中，设计类的方式多种多样，既可以通过继承来实现代码复用，又可以在类中添加另一个类的对象来实现。
4. 实验任务4
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();
}
运行结果：
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？
答：cin.ignore函数用于忽略输入流中的字符。这行代码通常用于清除输入缓冲区中的剩余字符，特别是在读取用户输入后，可能会有多余的字符（例如换行符）留在输入缓冲区中，使用这行代码可以确保输入缓冲区被清空，避免对后续输入操作产生影响。
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();
}
运行结果：
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();
}
运行结果：
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？
答：line16的作用是清除输入缓冲区中的剩余字符，防止输入操作出现错误。去掉这行代码程序可能因为输入缓冲区中的遗留字符而出现错误。
5. 实验任务5
task_5.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<iostream>
using namespace std;
template<typename T>
class GameResourceManager{
private:
T resource;
public:
GameResourceManager(T init):resource(init){}
T get(){
return resource;
}
void update(T change){
resource+=change;
if(resource<0){
resource=0;
}
}
};
6.实验任务6
info.hpp
#include<iostream>
#include<string>
using namespace std;
class Info{
public:
Info(const string& nickname,const string& contact,const string& city,int n):nickname(nickname),contact(contact),city(city),n(n){}
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;
}
private:
string nickname;
string contact;
string city;
int n;
};
task6.cpp
#include <iostream>
#include <vector>
#include<string>
#include<limits>
#include "info.hpp"
using namespace std;
int main() {
const int capacity = 100;
vector<Info> audience_list;
string nickname, contact, city;
int n,current_capacity=0;
char choice;
cout<<"昵称 "<<"联系方式(邮箱/手机号) "<<"所在城市 "<<"预定参加人数"<<endl;
while(cin>>nickname>>contact>>city>>n){
cin.ignore(numeric_limits<streamsize>::max(), '\n');
if(current_capacity+n>capacity){
cout<<"对不起，只剩"<<(capacity-current_capacity)<<"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>>choice;
if(choice=='u'){
cout<<"请重新输入预定信息："<<endl;
cin>>nickname>>contact>>city>>n;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
else
continue;
}
if(current_capacity + n <= capacity){
audience_list.push_back(Info(nickname, contact, city, n));
current_capacity += n;
}
}
cout << "截至目前，一共有" << current_capacity << "位听众预约。预约听众信息如下:\n";
std::cout << "------------------------\n";
for (const auto& info : audience_list) {
info.display();
std::cout << "------------------------\n";
}
return 0;
}
运行结果：
7.实验任务7
data.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
#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.
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();
}
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;
}