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; }
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