实验4 类的组合、继承、模板类、标准库
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) / 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.
存储在类的声明中用vector申请的空间里
通过类自带的this指针，用begin(),end()来访问；push_back来输入。
问题2
分母作用：分子为总成绩，除以分母（人数）后得到平均值；去掉1.0后运行结果如下
平均值只有整数结果；
总成绩和人数n都是整型，相除默认是整型，乘以1.0才能得到浮点型结果；
问题3
为了后续函数操作，成绩的存储空间设为public；数据有安全问题；
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; // 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.
成绩储存在为类成员grades申请的空间里；通过gades用begin(),end()访问；
问题2.
数据的存储方式，接口等等都要根据具体需求设计，要具体考虑访问权限等问题。
task4：
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(); }
运行结果：
问题1
语句的作用是忽略输入流中的字符，直到遇到换行符\n或者达到指定的字符数。
如图，注释后前面没接收完的字符可能被test2接收
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
结果如图；
第16行语句作用是让getline()不会接收到上一次循环输出的空行
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(); }
运行结果：
task6:
info.hpp:
#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(); } }
运行结果：
task7:
date.h,
#ifndef __DATE_H__ #define __DATE_H__ class Date { //日期类 private: int year; //年 int month; //月 int day; //日 int totalDays; //该日期是从公元元年1月1日开始的第儿天 public: Date(int year, int month, int day); //用年、月、日构造日期 int getYear() const { return year; } int getMonth() const { return month; } int getDay() const { return day; } int getMaxDay() const; //获得当月有多少天 bool isLeapYear()const { //判断当年是否为闰年 return year % 4 == 0 && year % 100 != 0 || year % 400 == 0; } void show() const; //输出当前日期 //计算两个日期之间差多少天 int dístance(const Date& date) const { return totalDays - date.totalDays; } }; #endif / / _DATE_H__
date.cpp,
#include "date.h" #include <iostream> #include <cstdlib> using namespace std; namespace { //namespace使下面的定义只在当前文件中有效 //存储平年中的某个月1日之前有多少天，为便于getMaxDay函数的实现，该数组多出一项 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,
#ifndef __ACCUMULATOR_H__ #define __ACCUMULATOR_H__ #include"date.h" class Accumulator { //将某个数值按日累加 private: Date lastDate; //上次变更数值的时期 double value; //数值的当前值 double sum; //数值按日累加之和 public: //构造函数，date为开始累加的日期，value为初始值 Accumulator(const Date& date, double value) :lastDate(date), value(value), sum(0){} //获得到日期date的累加结果 double getSum(const Date& date) const{ return sum + value * date.dístance(lastDate); } //在date将数值变更为value void change(const Date& date, double value){ sum = getSum(date); lastDate = date; this->value = value; } //初始化，将日期变为date，数值变为value，累加器清零 void reset(const Date& date, double value){ lastDate = date; this->value = value; sum = 0; } }; #endif//__ACCUMULATOR_H__
account.h,
#ifndef _ACCOUNT_H__ #define _ACCOUNT_H__ #include "date.h" #include "accumulator.h" #include <string> class Account { //账户类 private: std::string id; //账号 double balance; //余额 static double total; //所有账户的总金额 protected: //供派生类调用的构造两数，id为账户 Account(const Date& date, const std::string &id); //记录一笔账，date为日期，amount为金额，desc为说明 void record(const Date& date, double amount, const std::string& desc); //报告错误信息 void error(const std::string& msg) const; public: const std::string sgetId() const { return id; } double getBalance() const { return balance; } static double getTotal() { return total; } //显示账户信息 void show() const; }; class SavingsAccount : public Account { //储蓄账户类 private: Accumulator acc; //辅助计算利息的累加器 double rate; //存款的年利率 public: //构造函数 SavingsAccount(const Date& date, const std::string& id, double rate); double getRate() const { return rate; } //存入现金 void deposit(const Date& date, double amount, const std::string& desc); //取出现金 void withdraw(const Date& date, double amount, const std::string& desc); void settle(const Date& date); //结算利息，每年1月1日调用一次该函数 }; class CreditAccount : public Account{ //信用账户类 private: Accumulator acc; //辅助计算利息的累加器 double credit; //信用额度 double rate; //欠款的日利率 double fee; //信用卡年费 double getDebt() const { //获得欠款额 double balance = getBalance(); return (balance < 0 ? balance : 0); } public: //构造函数 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 getFee() const { return fee; } double getAvailableCredit() const {//获得可用信用 if (getBalance() < 0) return credit + getBalance(); else return credit; } //存入现金 void deposit(const Date & date, double amount, const std::string &desc); //取出现金 void withdraw(const Date & date, double amount, const std::string &desc); void settle(const Date & date); //结算利息和年费，每月1日调用一次该函数 void show() const; }; #endif//__ACCOUNT_H__
account.cpp,
#include"account.h" #include <cmath> #include <iostream> using namespace std; double Account::total = 0; //Account类的实现 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; //保留小数点后两位 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 类相关成员函数的实现 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 //计算年息 /date.dístance(Date(date.getYear() - 1, 1, 1)); if (interest != 0) record(date, interest, "interest"); acc.reset(date, getBalance()); } //CreditAccount类相关成员函数的实现 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(); }
7_10.cpp
#include "account.h" #include <iostream> using namespace std; int main() { Date date(2008, 11, 1); //起始日期 //建立几个账户 SavingsAccount sa1(date, "S3755217", 0.015); SavingsAccount sa2(date, "02342342", 0.015); CreditAccount ca(date, "C5392394", 10000, 0.0005, 50); //11月份的几笔账目 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"); //结算信用卡 ca.settle(Date(2008, 12, 1)); //12月份的几笔账目 ca.deposit(Date(2008, 12, 1), 2016, "repay the credit"); sa1.deposit(Date(2008, 12, 5), 5500, "salary"); //结算所有账户 sa1.settle(Date(2009, 1, 1)); sa2.settle(Date(2009, 1, 1)); ca.settle(Date(2009, 1, 1)); //输出各个账户信息 cout << endl; sa1.show(); cout << endl; sa2.show(); cout << endl; ca.show(); cout << endl; cout << "Tota1 :" << Account::getTotal() << endl; return 0; }
运行结果：
总结：
改进：一些类之间的数据传输改成以继承的方式；
缺陷：成员函数声明定义时需要注意
