实验3
task1:
1 #pragma once 2 3 #include <iostream> 4 #include <string> 5 6 using std::string; 7 using std::cout; 8 9 // 按钮类 10 class Button { 11 public: 12 Button(const string &text); 13 string get_label() const; 14 void click(); 15 16 private: 17 string label; 18 }; 19 20 Button::Button(const string &text): label{text} { 21 } 22 23 inline string Button::get_label() const { 24 return label; 25 } 26 27 void Button::click() { 28 cout << "Button '" << label << "' clicked\n"; 29 } 30 31 #pragma once 32 #include "button.hpp" 33 #include <vector> 34 #include <iostream> 35 36 using std::vector; 37 using std::cout; 38 using std::endl; 39 40 // 窗口类 41 class Window{ 42 public: 43 Window(const string &win_title); 44 void display() const; 45 void close(); 46 void add_button(const string &label); 47 48 private: 49 string title; 50 vector<Button> buttons; 51 }; 52 53 Window::Window(const string &win_title): title{win_title} { 54 buttons.push_back(Button("close")); 55 } 56 57 inline void Window::display() const { 58 string s(40, '*'); 59 60 cout << s << endl; 61 cout << "window title: " << title << endl; 62 cout << "It has " << buttons.size() << " buttons: " << endl; 63 for(const auto &i: buttons) 64 cout << i.get_label() << " button" << endl; 65 cout << s << endl; 66 } 67 68 void Window::close() { 69 cout << "close window '" << title << "'" << endl; 70 buttons.at(0).click(); 71 } 72 73 void Window::add_button(const string &label) { 74 buttons.push_back(Button(label)); 75 } 76 #include "window.hpp" 77 #include <iostream> 78 79 using std::cout; 80 using std::cin; 81 82 void test() { 83 Window w1("new window"); 84 w1.add_button("maximize"); 85 w1.display(); 86 w1.close(); 87 } 88 89 int main() { 90 cout << "用组合类模拟简单GUI:\n"; 91 test(); 92 }
问题1：定义了button类和window类，使用了标准库中的string类和vector类，window类和button类之间存在组合关系
问题2：如果一个成员函数不修改类的成员变量，那么它可以被声明为const成员函数。如果Button类和Window类中的某些函数体较小且调用频繁，可以考虑设置为inline。但是，过度使用inline可能会导致代码膨胀，因此需要谨慎使用。
问题3：创建一个包含 40 个星号‘*’的string对象s。
task2:
1 #include <iostream> 2 #include <vector> 3 4 using namespace std; 5 6 void output1(const vector<int> &v) { 7 for(auto &i: v) 8 cout << i << ", "; 9 cout << "\b\b \n"; 10 } 11 12 void output2(const vector<vector<int>> v) { 13 for(auto &i: v) { 14 for(auto &j: i) 15 cout << j << ", "; 16 cout << "\b\b \n"; 17 } 18 } 19 20 void test1() { 21 vector<int> v1(5, 42); 22 const vector<int> v2(v1); 23 24 v1.at(0) = -999; 25 cout << "v1: "; output1(v1); 26 cout << "v2: "; output1(v2); 27 cout << "v1.at(0) = " << v1.at(0) << endl; 28 cout << "v2.at(0) = " << v2.at(0) << endl; 29 } 30 31 void test2() { 32 vector<vector<int>> v1{{1, 2, 3}, {4, 5, 6, 7}}; 33 const vector<vector<int>> v2(v1); 34 35 v1.at(0).push_back(-999); 36 cout << "v1: \n"; output2(v1); 37 cout << "v2: \n"; output2(v2); 38 39 vector<int> t1 = v1.at(0); 40 cout << t1.at(t1.size()-1) << endl; 41 42 const vector<int> t2 = v2.at(0); 43 cout << t2.at(t2.size()-1) << endl; 44 } 45 46 int main() { 47 cout << "测试1:\n"; 48 test1(); 49 50 cout << "\n测试2:\n"; 51 test2(); 52 }
问题1：
问题2：
问题3：
问题4:深复制；需要提供一个const成员函数作为接口。
task3:
1 #pragma once 2 3 #include <iostream> 4 #include <cassert> 5 6 using std::cout; 7 using std::endl; 8 9 // 动态int数组对象类 10 class vectorInt{ 11 public: 12 vectorInt(int n); 13 vectorInt(int n, int value); 14 vectorInt(const vectorInt &vi); 15 ~vectorInt(); 16 17 int& at(int index); 18 const int& at(int index) const; 19 20 vectorInt& assign(const vectorInt &v); 21 int get_size() const; 22 23 private: 24 int size; 25 int *ptr; // ptr指向包含size个int的数组 26 }; 27 28 vectorInt::vectorInt(int n): size{n}, ptr{new int[size]} { 29 } 30 31 vectorInt::vectorInt(int n, int value): size{n}, ptr{new int[size]} { 32 for(auto i = 0; i < size; ++i) 33 ptr[i] = value; 34 } 35 36 vectorInt::vectorInt(const vectorInt &vi): size{vi.size}, ptr{new int[size]} { 37 for(auto i = 0; i < size; ++i) 38 ptr[i] = vi.ptr[i]; 39 } 40 41 vectorInt::~vectorInt() { 42 delete [] ptr; 43 } 44 45 const int& vectorInt::at(int index) const { 46 assert(index >= 0 && index < size); 47 48 return ptr[index]; 49 } 50 51 int& vectorInt::at(int index) { 52 assert(index >= 0 && index < size); 53 54 return ptr[index]; 55 } 56 57 vectorInt& vectorInt::assign(const vectorInt &v) { 58 delete[] ptr; // 释放对象中ptr原来指向的资源 59 60 size = v.size; 61 ptr = new int[size]; 62 63 for(int i = 0; i < size; ++i) 64 ptr[i] = v.ptr[i]; 65 66 return *this; 67 } 68 69 int vectorInt::get_size() const { 70 return size; 71 } 72 #include <iostream> 73 74 using std::cin; 75 using std::cout; 76 77 void output(const vectorInt &vi) { 78 for(auto i = 0; i < vi.get_size(); ++i) 79 cout << vi.at(i) << ", "; 80 cout << "\b\b \n"; 81 } 82 83 84 void test1() { 85 int n; 86 cout << "Enter n: "; 87 cin >> n; 88 89 vectorInt x1(n); 90 for(auto i = 0; i < n; ++i) 91 x1.at(i) = i*i; 92 cout << "x1: "; output(x1); 93 94 vectorInt x2(n, 42); 95 vectorInt x3(x2); 96 x2.at(0) = -999; 97 cout << "x2: "; output(x2); 98 cout << "x3: "; output(x3); 99 } 100 101 void test2() { 102 const vectorInt x(5, 42); 103 vectorInt y(10, 0); 104 105 cout << "y: "; output(y); 106 y.assign(x); 107 cout << "y: "; output(y); 108 109 cout << "x.at(0) = " << x.at(0) << endl; 110 cout << "y.at(0) = " << y.at(0) << endl; 111 } 112 113 int main() { 114 cout << "测试1: \n"; 115 test1(); 116 117 cout << "\n测试2: \n"; 118 test2(); 119 }
问题1：由于新对象的ptr指向的是新分配的内存空间，并且元素是从被复制对象逐个复制过来的，而不是简单地复制指针，所以这个复制构造函数实现的是深复制。
问题2：不能正确运行；这个const成员函数用于在const对象上访问元素。如果去掉const，那么在使用const对象调用at()函数时会出现问题。这就存在潜在的安全隐患，因为它违反了const对象的常量性原则，可能会导致在不应该修改对象的情况下意外地修改了对象。
task4:
1 #include <iostream> 2 #include <cassert> 3 4 using std::cout; 5 using std::endl; 6 7 // 类Matrix的声明 8 class Matrix { 9 public: 10 Matrix(int n, int m); // 构造函数，构造一个n*m的矩阵, 初始值为value 11 Matrix(int n); // 构造函数，构造一个n*n的矩阵, 初始值为value 12 Matrix(const Matrix &x); // 复制构造函数， 使用已有的矩阵X构造 13 ~Matrix(); 14 15 void set(const double *pvalue); // 用pvalue指向的连续内存块数据按行为矩阵赋值 16 void clear(); // 把矩阵对象的值置0 17 18 const double& at(int i, int j) const; // 返回矩阵对象索引(i,j)的元素const引用 19 double& at(int i, int j); // 返回矩阵对象索引(i,j)的元素引用 20 21 int get_lines() const; // 返回矩阵对象行数 22 int get_cols() const; // 返回矩阵对象列数 23 24 void display() const; // 按行显示矩阵对象元素值 25 26 private: 27 int lines; // 矩阵对象内元素行数 28 int cols; // 矩阵对象内元素列数 29 double *ptr; 30 }; 31 #include <iostream> 32 #include <cassert> 33 using std::cout; 34 using std::endl; 35 36 // 构造函数，构造一个 n*m 的矩阵, 初始值为默认值（未指定，这里假设为 0） 37 Matrix::Matrix(int n, int m) : lines{n}, cols{m}, ptr{new double[n * m]} { 38 for (int i = 0; i < n * m; ++i) { 39 ptr[i] = 0; 40 } 41 } 42 43 // 构造函数，构造一个 n*n 的矩阵, 初始值为默认值（未指定，这里假设为 0） 44 Matrix::Matrix(int n) : lines{n}, cols{n}, ptr{new double[n * n]} { 45 for (int i = 0; i < n * n; ++i) { 46 ptr[i] = 0; 47 } 48 } 49 50 // 复制构造函数，使用已有的矩阵 X 构造 51 Matrix::Matrix(const Matrix& x) : lines{x.lines}, cols{x.cols}, ptr{new double[x.lines * x.cols]} { 52 for (int i = 0; i < x.lines * x.cols; ++i) { 53 ptr[i] = x.ptr[i]; 54 } 55 } 56 57 // 析构函数 58 Matrix::~Matrix() { 59 delete[] ptr; 60 } 61 62 // 用 pvalue 指向的连续内存块数据按行为矩阵对象赋值 63 void Matrix::set(const double* pvalue) { 64 for (int i = 0; i < lines * cols; ++i) { 65 ptr[i] = pvalue[i]; 66 } 67 } 68 69 // 把矩阵对象的值置 0 70 void Matrix::clear() { 71 for (int i = 0; i < lines * cols; ++i) { 72 ptr[i] = 0; 73 } 74 } 75 76 // 返回矩阵对象索引(i,j)的元素引用 77 double& Matrix::at(int i, int j) { 78 assert(i >= 0 && i < lines && j >= 0 && j < cols); 79 return ptr[i * cols + j]; 80 } 81 82 // 返回矩阵对象索引(i,j)的元素 const 引用 83 const double& Matrix::at(int i, int j) const { 84 assert(i >= 0 && i < lines && j >= 0 && j < cols); 85 return ptr[i * cols + j]; 86 } 87 88 // 返回矩阵对象行数 89 int Matrix::get_lines() const { 90 return lines; 91 } 92 93 // 返回矩阵对象列数 94 int Matrix::get_cols() const { 95 return cols; 96 } 97 98 // 按行显示矩阵对象元素值 99 void Matrix::display() const { 100 for (int i = 0; i < lines; ++i) { 101 for (int j = 0; j < cols; ++j) { 102 cout << at(i, j) << ", "; 103 } 104 cout << "\b\b \n"; 105 } 106 } 107 #include <iostream> 108 #include <cassert> 109 110 using std::cin; 111 using std::cout; 112 using std::endl; 113 114 115 const int N = 1000; 116 117 // 输出矩阵对象索引为index所在行的所有元素 118 void output(const Matrix &m, int index) { 119 assert(index >= 0 && index < m.get_lines()); 120 121 for(auto j = 0; j < m.get_cols(); ++j) 122 cout << m.at(index, j) << ", "; 123 cout << "\b\b \n"; 124 } 125 126 127 void test1() { 128 double x[1000] = {1, 2, 3, 4, 5, 6, 7, 8, 9}; 129 130 int n, m; 131 cout << "Enter n and m: "; 132 cin >> n >> m; 133 134 Matrix m1(n, m); // 创建矩阵对象m1, 大小n×m 135 m1.set(x); // 用一维数组x的值按行为矩阵m1赋值 136 137 Matrix m2(m, n); // 创建矩阵对象m1, 大小m×n 138 m2.set(x); // 用一维数组x的值按行为矩阵m1赋值 139 140 Matrix m3(2); // 创建一个2×2矩阵对象 141 m3.set(x); // 用一维数组x的值按行为矩阵m4赋值 142 143 cout << "矩阵对象m1: \n"; m1.display(); cout << endl; 144 cout << "矩阵对象m2: \n"; m2.display(); cout << endl; 145 cout << "矩阵对象m3: \n"; m3.display(); cout << endl; 146 } 147 148 void test2() { 149 Matrix m1(2, 3); 150 m1.clear(); 151 152 const Matrix m2(m1); 153 m1.at(0, 0) = -999; 154 155 cout << "m1.at(0, 0) = " << m1.at(0, 0) << endl; 156 cout << "m2.at(0, 0) = " << m2.at(0, 0) << endl; 157 cout << "矩阵对象m1第0行: "; output(m1, 0); 158 cout << "矩阵对象m2第0行: "; output(m2, 0); 159 } 160 161 int main() { 162 cout << "测试1: \n"; 163 test1(); 164 165 cout << "测试2: \n"; 166 test2(); 167 }
task5:
1 #include <iostream> 2 #include <string> 3 #include <vector> 4 class User { 5 private: 6 std::string name; 7 std::string password; 8 std::string email; 9 10 public: 11 User(const std::string& n, const std::string& p = "123456", const std::string& e = ""); 12 void set_email(); 13 void change_password(); 14 void display(); 15 }; 16 17 // 类成员函数的实现直接放在这里 18 User::User(const std::string& n, const std::string& p, const std::string& e) : name(n), password(p), email(e) {} 19 20 void User::set_email() { 21 std::string input_email; 22 while (true) { 23 std::cout << "Please enter your email: "; 24 std::cin >> input_email; 25 bool has_at = false; 26 for (char c : input_email) { 27 if (c == '@') { 28 has_at = true; 29 break; 30 } 31 } 32 if (has_at) { 33 email = input_email; 34 break; 35 } else { 36 std::cout << "Invalid email. Please try again." << std::endl; 37 } 38 } 39 } 40 41 void User::change_password() { 42 int attempts = 0; 43 while (attempts < 3) { 44 std::string old_password; 45 std::cout << "Please enter your old password: "; 46 std::cin >> old_password; 47 if (old_password == password) { 48 std::string new_password; 49 std::cout << "Please enter your new password: "; 50 std::cin >> new_password; 51 password = new_password; 52 break; 53 } else { 54 attempts++; 55 std::cout << "Incorrect password. Attempts left: " << 3 - attempts << std::endl; 56 } 57 } 58 if (attempts == 3) { 59 std::cout << "Too many incorrect attempts. Try again later." << std::endl; 60 } 61 } 62 63 void User::display() { 64 std::string masked_password; 65 for (size_t i = 0; i < password.length(); ++i) { 66 masked_password += '*'; 67 } 68 std::cout << "Name: " << name << ", Password: " << masked_password << ", Email: " << email << std::endl; 69 } 70 71 72 73 74 using std::cin; 75 using std::cout; 76 using std::endl; 77 using std::vector; 78 using std::string; 79 80 void test() { 81 vector<User> user_lst; 82 83 User u1("Alice", "2024113", "Alice@hotmail.com"); 84 user_lst.push_back(u1); 85 cout << endl; 86 87 User u2("Bob"); 88 u2.set_email(); 89 u2.change_password(); 90 user_lst.push_back(u2); 91 cout << endl; 92 93 User u3("Hellen"); 94 u3.set_email(); 95 u3.change_password(); 96 user_lst.push_back(u3); 97 cout << endl; 98 99 cout << "There are " << user_lst.size() << " users. they are: " << endl; 100 for(auto &i: user_lst) { 101 i.display(); 102 cout << endl; 103 } 104 } 105 106 int main() { 107 test(); 108 }
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 }; 22 23 24 25 #include"date.h" 26 #include<iostream> 27 #include<cstdlib> 28 using namespace std; 29 namespace { 30 const int DAYS_BEFIRE_MONTH[] = { 0,31,59,90,120,151,181,212,243,273,304 ,334,365 }; 31 } 32 Date::Date(int year, int month, int day) :year(year), month(month), day(day) { 33 if (day <= 0 || day > getMaxDay()) { 34 cout << "Invalid date: "; 35 show(); 36 cout << endl; 37 exit(1); 38 } 39 int years = year - 1; 40 totalDays = years * 365 + years / 4 - years / 100 + years / 400 + DAYS_BEFIRE_MONTH[month - 1] + day; 41 if (isLeapYear() && month > 2) totalDays++; 42 } 43 int Date::getMaxDay()const { 44 if (isLeapYear() &&month == 2) 45 return 29; 46 else return DAYS_BEFIRE_MONTH[month] - DAYS_BEFIRE_MONTH[month - 1]; 47 } 48 void Date::show()const { 49 cout << getYear() << "-" << getMonth() << "-" << getDay(); 50 } 51 52 53 54 #pragma once 55 #include"date.h" 56 #include<string> 57 using namespace std; 58 class SavingsAccount { 59 private: 60 string id; 61 double balance; 62 double rate; 63 Date lastDate; 64 double accumulation; 65 static double total; 66 void record(const Date& date, double amount, const string& desc); 67 void error(const string& msg) const; 68 double accumulate(const Date& date)const { 69 return accumulation + balance * date.distance(lastDate); 70 } 71 public: 72 SavingsAccount(const Date& date, const string& id, double rate); 73 const string& getId()const { return id; } 74 double getBalance()const { return balance; } 75 double getRate()const { return rate; } 76 static double getTotal() { return total; } 77 void deposit(const Date& date, double amount, const string& desc); 78 void withdraw(const Date& date, double amount, const string& desc); 79 void settle(const Date& date); 80 void show() const; 81 }; 82 83 84 85 #include"account.h" 86 #include<cmath> 87 #include<iostream> 88 using namespace std; 89 double SavingsAccount::total = 0; 90 SavingsAccount::SavingsAccount(const Date& date, const string& id, double rate) : 91 id(id), balance(0), rate(rate), lastDate(date), accumulation(0) { 92 date.show(); 93 cout << "\t#" << id << "created" << endl; 94 } 95 void SavingsAccount::record(const Date& date, double amount, const string& desc) { 96 accumulation = accumulate(date); 97 lastDate = date; 98 amount = floor(amount * 100 + 0.5) / 100; 99 balance += amount; 100 total += amount; 101 date.show(); 102 cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl; 103 } 104 void SavingsAccount::error(const string& msg) const { 105 cout << "Error(#" << id << "):" << msg << endl; 106 } 107 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) { 108 record(date, amount, desc); 109 } 110 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) { 111 if (amount > getBalance()) 112 error("not enough money"); 113 else 114 record(date, -amount, desc); 115 } 116 void SavingsAccount::settle(const Date& date) { 117 double interest = accumulate(date) * rate / date.distance(Date(date.getYear() - 1, 1, 1)); 118 if (interest != 0) record( date,interest,"interest" ); 119 accumulation = 0; 120 } 121 void SavingsAccount::show()const { 122 cout << id << "\tBalance: " << balance; 123 } 124 125 126 #include"account.h" 127 #include<iostream> 128 using namespace std; 129 int main() { 130 Date date{ 2008,11,1 }; 131 SavingsAccount accounts[] = { 132 SavingsAccount(date,"03755217",0.015), 133 SavingsAccount(date,"02342342",0.015) 134 }; 135 const int n = sizeof(accounts) / sizeof(SavingsAccount); 136 accounts[0].deposit(Date(2008, 11, 5), 5000, "salary"); 137 accounts[1].deposit(Date(2008, 11, 25), 10000, "sell stock 0323"); 138 accounts[0].deposit(Date(2008, 12, 5), 5500, "salary"); 139 accounts[1].withdraw(Date(2008, 12, 20), 4000, "buy a laptop"); 140 cout << endl; 141 for (int i = 0; i < n; i++) { 142 accounts[i].settle(Date(2009, 1, 1)); 143 accounts[i].show(); 144 cout << endl; 145 } 146 cout << "Total: " << SavingsAccount::getTotal() << endl; 147 return 0; 148 }
