实验4
task2
1 #include <iostream> 2 #include <vector> 3 #include <string> 4 #include <algorithm> 5 #include <numeric> 6 #include <iomanip> 7 8 using std::vector; 9 using std::string; 10 using std::cin; 11 using std::cout; 12 using std::endl; 13 14 class GradeCalc: public vector<int> { 15 public: 16 GradeCalc(const string &cname, int size); 17 void input(); // 录入成绩 18 void output() const; // 输出成绩 19 void sort(bool ascending = false); // 排序 (默认降序) 20 int min() const; // 返回最低分 21 int max() const; // 返回最高分 22 float average() const; // 返回平均分 23 void info(); // 输出课程成绩信息 24 25 private: 26 void compute(); // 成绩统计 27 28 private: 29 string course_name; // 课程名 30 int n; // 课程人数 31 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] 32 vector<double> rates = vector<double>(5, 0); // 保存各分数段比例 33 }; 34 35 GradeCalc::GradeCalc(const string &cname, int size): course_name{cname}, n{size} {} 36 37 void GradeCalc::input() { 38 int grade; 39 40 for(int i = 0; i < n; ++i) { 41 cin >> grade; 42 this->push_back(grade); 43 } 44 } 45 46 void GradeCalc::output() const { 47 for(auto ptr = this->begin(); ptr != this->end(); ++ptr) 48 cout << *ptr << " "; 49 cout << endl; 50 } 51 52 void GradeCalc::sort(bool ascending) { 53 if(ascending) 54 std::sort(this->begin(), this->end()); 55 else 56 std::sort(this->begin(), this->end(), std::greater<int>()); 57 } 58 59 int GradeCalc::min() const { 60 return *std::min_element(this->begin(), this->end()); 61 } 62 63 int GradeCalc::max() const { 64 return *std::max_element(this->begin(), this->end()); 65 } 66 67 float GradeCalc::average() const { 68 return std::accumulate(this->begin(), this->end(), 0) * 1.0 / n; 69 } 70 71 void GradeCalc::compute() { 72 for(int grade: *this) { 73 if(grade < 60) 74 counts.at(0)++; 75 else if(grade >= 60 && grade < 70) 76 counts.at(1)++; 77 else if(grade >= 70 && grade < 80) 78 counts.at(2)++; 79 else if(grade >= 80 && grade < 90) 80 counts.at(3)++; 81 else if(grade >= 90) 82 counts.at(4)++; 83 } 84 85 for(int i = 0; i < rates.size(); ++i) 86 rates.at(i) = counts.at(i) * 1.0 / n; 87 } 88 89 void GradeCalc::info() { 90 cout << "课程名称:\t" << course_name << endl; 91 cout << "排序后成绩: \t"; 92 sort(); output(); 93 cout << "最高分:\t" << max() << endl; 94 cout << "最低分:\t" << min() << endl; 95 cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << endl; 96 97 compute(); // 统计各分数段人数、比例 98 99 vector<string> tmp{"[0, 60) ", "[60, 70)", "[70, 80)","[80, 90)", "[90, 100]"}; 100 for(int i = tmp.size()-1; i >= 0; --i) 101 cout << tmp[i] << "\t: " << counts[i] << "人\t" 102 << std::fixed << std::setprecision(2) << rates[i]*100 << "%" << endl; 103 }
1 #include "GradeCalc.hpp" 2 #include <iomanip> 3 4 void test() { 5 int n; 6 cout << "输入班级人数: "; 7 cin >> n; 8 9 GradeCalc c1("OOP", n); 10 11 cout << "录入成绩: " << endl;; 12 c1.input(); 13 cout << "输出成绩: " << endl; 14 c1.output(); 15 16 cout << string(20, '*') + "课程成绩信息" + string(20, '*') << endl; 17 c1.info(); 18 } 19 20 int main() { 21 test(); 22 }
问题1：1.存储在vector<int>继承的容器。2.通过vector<int>继承来的成员函数接口访问。begin()、end()。3.通过vector<int>的成员函数接口push_back存入。
问题2：除以分母n得到平均分。有影响，比如整数除法7/2结果为3而不是3.5。乘以1.0进行浮点数除法。
问题3：应检查成绩范围。真实应用应在0-100范围。输入类型检查或者改进使其支持浮点数。
task3
1 #include <iostream> 2 #include <vector> 3 #include <string> 4 #include <algorithm> 5 #include <numeric> 6 #include <iomanip> 7 8 using std::vector; 9 using std::string; 10 using std::cin; 11 using std::cout; 12 using std::endl; 13 14 class GradeCalc { 15 public: 16 GradeCalc(const string &cname, int size); 17 void input(); // 录入成绩 18 void output() const; // 输出成绩 19 void sort(bool ascending = false); // 排序 (默认降序) 20 int min() const; // 返回最低分 21 int max() const; // 返回最高分 22 float average() const; // 返回平均分 23 void info(); // 输出课程成绩信息 24 25 private: 26 void compute(); // 成绩统计 27 28 private: 29 string course_name; // 课程名 30 int n; // 课程人数 31 vector<int> grades; // 课程成绩 32 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] 33 vector<double> rates = vector<double>(5, 0); // 保存各分数段比例 34 }; 35 36 GradeCalc::GradeCalc(const string &cname, int size): course_name{cname}, n{size} {} 37 38 void GradeCalc::input() { 39 int grade; 40 41 for(int i = 0; i < n; ++i) { 42 cin >> grade; 43 grades.push_back(grade); 44 } 45 } 46 47 void GradeCalc::output() const { 48 for(int grade: grades) 49 cout << grade << " "; 50 cout << endl; 51 } 52 53 void GradeCalc::sort(bool ascending) { 54 if(ascending) 55 std::sort(grades.begin(), grades.end()); 56 else 57 std::sort(grades.begin(), grades.end(), std::greater<int>()); 58 59 } 60 61 int GradeCalc::min() const { 62 return *std::min_element(grades.begin(), grades.end()); 63 } 64 65 int GradeCalc::max() const { 66 return *std::max_element(grades.begin(), grades.end()); 67 } 68 69 float GradeCalc::average() const { 70 return std::accumulate(grades.begin(), grades.end(), 0) * 1.0 / n; 71 } 72 73 void GradeCalc::compute() { 74 for(int grade: grades) { 75 if(grade < 60) 76 counts.at(0)++; 77 else if(grade >= 60 && grade < 70) 78 counts.at(1)++; 79 else if(grade >= 70 && grade < 80) 80 counts.at(2)++; 81 else if(grade >= 80 && grade < 90) 82 counts.at(3)++; 83 else if(grade >= 90) 84 counts.at(4)++; 85 } 86 87 for(int i = 0; i < rates.size(); ++i) 88 rates.at(i) = counts.at(i) *1.0 / n; 89 } 90 91 void GradeCalc::info() { 92 cout << "课程名称:\t" << course_name << endl; 93 cout << "排序后成绩: \t"; 94 sort(); output(); 95 cout << "最高分:\t" << max() << endl; 96 cout << "最低分:\t" << min() << endl; 97 cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << endl; 98 99 compute(); // 统计各分数段人数、比例 100 101 vector<string> tmp{"[0, 60) ", "[60, 70)", "[70, 80)","[80, 90)", "[90, 100]"}; 102 for(int i = tmp.size()-1; i >= 0; --i) 103 cout << tmp[i] << "\t: " << counts[i] << "人\t" 104 << std::fixed << std::setprecision(2) << rates[i]*100 << "%" << endl; 105 }
1 #include "GradeCalc.hpp" 2 #include <iomanip> 3 4 void test() { 5 int n; 6 cout << "输入班级人数: "; 7 cin >> n; 8 9 GradeCalc c1("OOP", n); 10 11 cout << "录入成绩: " << endl;; 12 c1.input(); 13 cout << "输出成绩: " << endl; 14 c1.output(); 15 16 cout << string(20, '*') + "课程成绩信息" + string(20, '*') << endl; 17 c1.info(); 18 } 19 20 int main() { 21 test(); 22 }
问题1：组合类GradeCalc中，成绩存储在vector<int>grades这个成员变量中。
访问成绩的方式：
sort、min、max、average 方法：使用grades.begin()和grades.end()作为迭代器范围来访问成绩数据进行排序。
output 方法：通过一个范围for循环遍历grades向量，直接访问每个成绩元素并输出。
与实验任务 2 在代码写法细节上的差别
在实验任务 2 中，GradeCalc类是从vector<int>派生而来的，所以可以直接使用this->begin()和this->end()来访问成绩数据。而在实验任务 3 中，GradeCalc类是通过组合
（包含一个vector<int> grades成员变量）来存储成绩数据，因此在访问成绩数据时，需要使用grades.begin()和grades.end()。
问题 2
封装性：通过对比可以看到，无论是继承还是组合，都可以实现对数据和操作的封装。
task4_1
1 #include <iostream> 2 #include <string> 3 #include <limits> 4 5 using namespace std; 6 7 void test1() { 8 string s1, s2; 9 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 10 cout << "s1: " << s1 << endl; 11 cout << "s2: " << s2 << endl; 12 } 13 14 void test2() { 15 string s1, s2; 16 getline(cin, s1); // getline(): 从输入流中提取字符串，直到遇到换行符 17 getline(cin, s2); 18 cout << "s1: " << s1 << endl; 19 cout << "s2: " << s2 << endl; 20 } 21 22 void test3() { 23 string s1, s2; 24 getline(cin, s1, ' '); //从输入流中提取字符串，直到遇到指定分隔符 25 getline(cin, s2); 26 cout << "s1: " << s1 << endl; 27 cout << "s2: " << s2 << endl; 28 } 29 30 int main() { 31 cout << "测试1: 使用标准输入流对象cin输入字符串" << endl; 32 test1(); 33 cout << endl; 34 35 cin.ignore(numeric_limits<streamsize>::max(), '\n'); 36 37 cout << "测试2: 使用函数getline()输入字符串" << endl; 38 test2(); 39 cout << endl; 40 41 cout << "测试3: 使用函数getline()输入字符串, 指定字符串分隔符" << endl; 42 test3(); 43 }
问题1：
cin.ignore函数用于忽略输入流中的字符。
numeric_limits<streamsize>::max()返回streamsize类型能表示的最大值。用于指定要忽略的最大字符数。
'\n'是一个换行符，表示cin.ignore函数将忽略输入流中的字符，直到遇到换行符或者达到指定的最大字符数。
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
1 #include <iostream> 2 #include <string> 3 #include <vector> 4 #include <limits> 5 6 using namespace std; 7 8 void output(const vector<string> &v) { 9 for(auto &s: v) 10 cout << s << endl; 11 } 12 13 void test() { 14 int n; 15 while(cout << "Enter n: ", cin >> n) { 16 vector<string> v1; 17 18 for(int i = 0; i < n; ++i) { 19 string s; 20 cin >> s; 21 v1.push_back(s); 22 } 23 24 cout << "output v1: " << endl; 25 output(v1); 26 cout << endl; 27 } 28 } 29 30 int main() { 31 cout << "测试: 使用cin多组输入字符串" << endl; 32 test(); 33 }
task4_3
1 #include <iostream> 2 #include <string> 3 #include <vector> 4 #include <limits> 5 6 using namespace std; 7 8 void output(const vector<string> &v) { 9 for(auto &s: v) 10 cout << s << endl; 11 } 12 13 void test() { 14 int n; 15 while(cout << "Enter n: ", cin >> n) { 16 cin.ignore(numeric_limits<streamsize>::max(), '\n'); 17 18 vector<string> v2; 19 20 for(int i = 0; i < n; ++i) { 21 string s; 22 getline(cin, s); 23 v2.push_back(s); 24 } 25 cout << "output v2: " << endl; 26 output(v2); 27 cout << endl; 28 } 29 } 30 31 int main() { 32 cout << "测试: 使用函数getline()多组输入字符串" << endl; 33 test(); 34 }
问题2：
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。
task5
1 #include<iostream> 2 3 using namespace std; 4 5 template<typename T> 6 7 class GameResourceManager{ 8 private: 9 T resource; 10 public: 11 GameResourceManager(T init):resource(init){} 12 T get(){ 13 return resource; 14 } 15 void update(T change){ 16 resource+=change; 17 if(resource<0){ 18 resource=0; 19 } 20 } 21 };
1 #include "grm.hpp" 2 #include <iostream> 3 4 using std::cout; 5 using std::endl; 6 7 void test1() { 8 GameResourceManager<float> HP_manager(99.99); 9 cout << "当前生命值: " << HP_manager.get() << endl; 10 HP_manager.update(9.99); 11 cout << "增加9.99生命值后, 当前生命值: " << HP_manager.get() << endl; 12 HP_manager.update(-999.99); 13 cout <<"减少999.99生命值后, 当前生命值: " << HP_manager.get() << endl; 14 } 15 16 void test2() { 17 GameResourceManager<int> Gold_manager(100); 18 cout << "当前金币数量: " << Gold_manager.get() << endl; 19 Gold_manager.update(50); 20 cout << "增加50个金币后, 当前金币数量: " << Gold_manager.get() << endl; 21 Gold_manager.update(-99); 22 cout <<"减少99个金币后, 当前金币数量: " << Gold_manager.get() << endl; 23 } 24 25 26 int main() { 27 cout << "测试1: 用float类型对类模板GameResourceManager实例化" << endl; 28 test1(); 29 cout << endl; 30 31 cout << "测试2: 用int类型对类模板GameResourceManager实例化" << endl; 32 test2(); 33 }
task6
1 #include<iostream> 2 #include<string> 3 4 using namespace std; 5 6 class Info{ 7 public: 8 9 Info(const string& nickname,const string& contact,const string& city,int n):nickname(nickname),contact(contact),city(city),n(n){} 10 11 void display() const{ 12 cout<<"昵称："<<nickname<<endl; 13 cout<<"联系方式："<<contact<<endl; 14 cout<<"所在城市："<<city<<endl; 15 cout<<"预定人数："<<n<<endl; 16 } 17 18 private: 19 20 string nickname; 21 string contact; 22 string city; 23 int n; 24 };
1 #include <iostream> 2 #include <vector> 3 #include<string> 4 #include<limits> 5 #include "info.hpp" 6 7 using namespace std; 8 9 int main() { 10 const int capacity = 100; 11 vector<Info> audience_list; 12 string nickname, contact, city; 13 int n,current_capacity=0; 14 char choice; 15 cout<<"昵称 "<<"联系方式(邮箱/手机号) "<<"所在城市 "<<"预定参加人数"<<endl; 16 17 while(cin>>nickname>>contact>>city>>n){ 18 cin.ignore(numeric_limits<streamsize>::max(), '\n'); 19 if(current_capacity+n>capacity){ 20 cout<<"对不起，只剩"<<(capacity-current_capacity)<<"个位置."<<endl; 21 cout<<"1.输入u，更新（update)预定信息"<<endl; 22 cout<<"2.输入q，退出预定"<<endl; 23 cout<<"你的选择："; 24 cin>>choice; 25 if(choice=='u'){ 26 cout<<"请重新输入预定信息："<<endl; 27 cin>>nickname>>contact>>city>>n; 28 cin.ignore(numeric_limits<streamsize>::max(), '\n'); 29 } 30 else 31 continue; 32 } 33 if(current_capacity + n <= capacity){ 34 audience_list.push_back(Info(nickname, contact, city, n)); 35 current_capacity += n; 36 } 37 38 } 39 cout << "截至目前，一共有" << current_capacity << "位听众预约。预约听众信息如下:\n"; 40 std::cout << "------------------------\n"; 41 for (const auto& info : audience_list) { 42 info.display(); 43 std::cout << "------------------------\n"; 44 } 45 return 0; 46 }
task7
1 #pragma once 2 class Date{ 3 private: 4 int year; 5 int month; 6 int day; 7 int totalDays; 8 public: 9 Date(int year,int month,int day); 10 int getYear()const {return year;} 11 int getMonth()const{return month;} 12 int getDay()const{return day;} 13 int getMaxDay()const; 14 bool isLeapYear()const{ 15 return year%4==0&&year%100!=0||year%400==0; 16 } 17 void show()const; 18 int distance(const Date&date)const{ 19 return totalDays-date.totalDays; 20 } 21 };
1 #include"date.h" 2 #include<iostream> 3 #include<cstdlib> 4 using namespace std; 5 namespace{ 6 const int DAYS_BEFORE_MONTH[]={0,31,59,90,120,151,181,212,243,273,304,334,365}; 7 } 8 Date::Date(int year,int month,int day):year(year),month(month),day(day){ 9 if(day<=0||day>getMaxDay()){ 10 cout<<"Invalid date: "; 11 show(); 12 cout<<endl; 13 exit(1); 14 } 15 int years=year-1; 16 totalDays=years*365+years/4-years/100+years/400+DAYS_BEFORE_MONTH[month-1]+day; 17 if(isLeapYear()&&month>2)totalDays++; 18 } 19 int Date::getMaxDay()const{ 20 if(isLeapYear()&&month==2) 21 return 29; 22 else 23 return DAYS_BEFORE_MONTH[month]-DAYS_BEFORE_MONTH[month-1]; 24 } 25 void Date::show()const{ 26 cout<<getYear()<<"-"<<getMonth()<<"-"<<getDay(); 27 }
1 #pragma once 2 #include "date.h" 3 class Accumulator { 4 private: 5 Date lastDate; 6 double value; 7 double sum; 8 public: 9 Accumulator(const Date&date,double value):lastDate(date),value(value),sum{0}{} 10 double getSum(const Date& date) const { 11 return sum + value * date.distance(lastDate); 12 } 13 void change(const Date& date, double value) { 14 sum = getSum(date); 15 lastDate = date; 16 this->value = value; 17 } 18 void reset(const Date& date, double value) { 19 lastDate = date; 20 this->value; 21 sum = 0; 22 } 23 };
1 #pragma once 2 #include"date.h" 3 #include"accumulator.h" 4 #include<string> 5 using namespace std; 6 class Account { 7 private: 8 string id; 9 double balance; 10 static double total; 11 protected: 12 Account(const Date& date, const string &id); 13 void record(const Date& date, double amount, const string& desc); 14 void error(const string& msg) const; 15 public:const string& getId() { return id; } 16 double getBalance()const { return balance; } 17 static double getTotal() { return total; } 18 void show()const; 19 }; 20 class SavingsAccount:public Account { 21 private: 22 Accumulator acc; 23 double rate; 24 public: 25 SavingsAccount(const Date& date, const string& id, double rate); 26 double getRate() const { return rate; } 27 void deposit(const Date& date, double amount, const string& desc); 28 void withdraw(const Date& date, double amount, const string& desc); 29 void settle(const Date& date); 30 }; 31 class CreditAccount :public Account { 32 private: 33 Accumulator acc; 34 double credit; 35 double rate; 36 double fee; 37 double getDebt()const { 38 double balance = getBalance(); 39 return(balance < 0 ? balance : 0); 40 } 41 public:CreditAccount(const Date& date, const string& id, double credit, double rate, double fee); 42 double getCredit()const { return credit; } 43 double getRate()const { return rate; } 44 double getFee() const { return fee; } 45 double getAvailableCredit()const { 46 if (getBalance() < 0)return credit + getBalance(); 47 else return credit; 48 } 49 void deposit(const Date& date, double amount, const string& desc); 50 void withdraw(const Date& date, double amount, const string& desc); 51 void settle(const Date& date); 52 void show()const; 53 };
1 #include"account.h" 2 #include<cmath> 3 #include<iostream> 4 using namespace std; 5 double Account::total=0; 6 Account::Account(const Date &date,const string &id) 7 :id(id),balance(0){ 8 date.show();cout<<"\t#"<<id<<"created"<<endl; 9 } 10 void Account::record(const Date &date,double amount,const string &desc){ 11 amount=floor(amount*100+0.5)/100; 12 balance+=amount;total+=amount; 13 date.show(); 14 cout<<"\t#"<<id<<"\t"<<amount<<"\t"<<balance<<"\t"<<desc<<endl; 15 } 16 void Account::show()const{cout<<id<<"\tBalance:"<<balance;} 17 void Account::error(const string &msg)const{ 18 cout<<"Error(#"<<id<<"):"<<msg<<endl; 19 } 20 SavingsAccount::SavingsAccount(const Date&date,const string &id,double rate):Account(date,id),rate(rate),acc(date,0){} 21 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) { 22 record(date, amount, desc); 23 acc.change(date, getBalance()); 24 } 25 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) { 26 if (amount > getBalance()) { 27 error("not enough money"); 28 } 29 else { 30 record(date, -amount, desc); 31 acc.change(date, getBalance()); 32 } 33 } 34 void SavingsAccount::settle(const Date& date) { 35 double interest = acc.getSum(date) * rate/date.distance(Date(date.getYear()-1,1,1)); 36 if (interest != 0)record(date, interest, "interest"); 37 acc.reset(date, getBalance()); 38 } 39 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){} 40 void CreditAccount::deposit(const Date& date, double amount, const string& desc) { 41 record(date, amount, desc); 42 acc.change(date, getDebt()); 43 } 44 void CreditAccount::withdraw(const Date& date, double amount, const string& desc) { 45 if (amount - getBalance() > credit) { 46 error("not enouogh credit"); 47 } 48 else { 49 record(date, -amount, desc); 50 acc.change(date, getDebt()); 51 } 52 } 53 void CreditAccount::settle(const Date& date) { 54 double interest = acc.getSum(date) * rate; 55 if (interest != 0) record(date, interest, "interest"); 56 if (date.getMonth() == 1)record(date, -fee, "annual fee"); 57 acc.reset(date, getDebt()); 58 } 59 void CreditAccount::show()const { 60 Account::show(); 61 cout << "\tAvailable credit:" << getAvailableCredit(); 62 }
1 #include "account.h" 2 #include<iostream> 3 using namespace std; 4 int main() { 5 Date date(2008, 11, 1); 6 SavingsAccount sa1(date, "S3755217", 0.015); 7 SavingsAccount sa2(date, "02342342", 0.015); 8 CreditAccount ca(date, "C5392394", 10000, 0.0005, 50); 9 sa1.deposit(Date(2008, 11, 5), 5000, "Salary"); 10 ca.withdraw(Date(2008, 11, 15), 2000, "buy a cell"); 11 sa2.deposit(Date(2008, 11, 25), 10000, "sell stock 0323"); 12 ca.settle(Date(2008, 12, 1)); 13 ca.deposit(Date(2008, 12,1), 2016, "repay the credit"); 14 sa1.deposit(Date(2008, 12, 5), 5500, "salary"); 15 sa1.settle(Date(2009, 1, 1)); 16 sa2.settle(Date(2009, 1, 1)); 17 ca.settle(Date(2009, 1, 1)); 18 cout << endl; 19 sa1.show(); cout << endl; 20 sa2.show(); cout << endl; 21 ca.show(); cout << endl; 22 cout << "Total: " << Account::getTotal() << endl; 23 return 0; 24 }
