实验3 类和对象_基础编程2
实验任务一
1 #pragma once 2 #include <iostream> 3 #include <string> 4 5 using std::string; 6 using std::cout; 7 8 // 按钮类 9 class Button { 10 public: 11 Button(const string& text); 12 string get_label() const; 13 void click(); 14 15 private: 16 string label; 17 }; 18 19 Button::Button(const string& text) : label{ text } { 20 } 21 22 inline string Button::get_label() const { 23 return label; 24 } 25 26 void Button::click() { 27 cout << "Button '" << label << "' clicked\n"; 28 }
1 #pragma once 2 #include "button.hpp" 3 #include <vector> 4 #include <iostream> 5 6 using std::vector; 7 using std::cout; 8 using std::endl; 9 10 // 窗口类 11 class Window { 12 public: 13 Window(const string& win_title); 14 void display() const; 15 void close(); 16 void add_button(const string& label); 17 18 private: 19 string title; 20 vector<Button> buttons; 21 }; 22 23 Window::Window(const string& win_title) : title{ win_title } { 24 buttons.push_back(Button("close")); 25 } 26 27 inline void Window::display() const { 28 string s(40, '*'); 29 30 cout << s << endl; 31 cout << "window title: " << title << endl; 32 cout << "It has " << buttons.size() << " buttons: " << endl; 33 for (const auto& i : buttons) 34 cout << i.get_label() << " button" << endl; 35 cout << s << endl; 36 } 37 38 void Window::close() { 39 cout << "close window '" << title << "'" << endl; 40 buttons.at(0).click(); 41 } 42 43 void Window::add_button(const string& label) { 44 buttons.push_back(Button(label)); 45 }
1 #include "window.hpp" 2 #include <iostream> 3 4 using std::cout; 5 using std::cin; 6 7 void test() { 8 Window w1("new window"); 9 w1.add_button("maximize"); 10 w1.display(); 11 w1.close(); 12 } 13 14 int main() { 15 cout << "用组合类模拟简单GUI:\n"; 16 test(); 17 }
问题一：
自定义了两个类window,button,使用了标准库的string,vector，vector包含button，window包含vector，string则被button和window包含。
问题二：
不适合，它们有的改变了类成员，不能设为const函数，有的比较复杂，不适合做内联函数。
问题三：
构造的string可用作分割线。
实验任务二
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 }
问题一：
建立vector v1，其中有5个int元素，都为42；建立一个vector v2，用v1赋值；把v1中下表为0的元素改为-999。
问题二：
建立vector v1，其中有2个vector<int>元素；建立一个vector v2，用v1赋值，并设为常量；在v1中下表为0的元素，即第一个vector<int>后插入-999。
问题三：
建立vector t1，用v1中下表为0的元素，即第一个vector<int>赋值；输出t1的最后一项元素；建立vector t2，用v2中下表为0的元素，即第一个vector<int>赋值，因为v2是常量，所以t2必须也是常量；输出t2的最后一项元素。
实验任务三
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 }
1 #include "vectorInt.hpp" 2 #include <iostream> 3 4 using std::cin; 5 using std::cout; 6 7 void output(const vectorInt& vi) { 8 for (auto i = 0; i < vi.get_size(); ++i) 9 cout << vi.at(i) << ", "; 10 cout << "\b\b \n"; 11 } 12 13 14 void test1() { 15 int n; 16 cout << "Enter n: "; 17 cin >> n; 18 19 vectorInt x1(n); 20 for (auto i = 0; i < n; ++i) 21 x1.at(i) = i * i; 22 cout << "x1: "; output(x1); 23 24 vectorInt x2(n, 42); 25 vectorInt x3(x2); 26 x2.at(0) = -999; 27 cout << "x2: "; output(x2); 28 cout << "x3: "; output(x3); 29 } 30 31 void test2() { 32 const vectorInt x(5, 42); 33 vectorInt y(10, 0); 34 35 cout << "y: "; output(y); 36 y.assign(x); 37 cout << "y: "; output(y); 38 39 cout << "x.at(0) = " << x.at(0) << endl; 40 cout << "y.at(0) = " << y.at(0) << endl; 41 } 42 43 int main() { 44 cout << "测试1: \n"; 45 test1(); 46 47 cout << "\n测试2: \n"; 48 test2(); 49 }
问题一：
深复制。
问题二：
不行，不返回引用类型无法对原对象操作；不行，不设为const，若ptr值改变，会导致内存泄漏。
问题三：
可以，返回值不使用引用产生的副本是浅复制，是两个不一样但指向相同地址的指针（这个类主要就是个指针）。这样不会占用很多额外内存，对指针指向成员操作也是互通的。但两个指向相同地址的指针容易导致混淆，后续想析构时也很麻烦，所以还是推荐返回值使用引用。
实验任务四
matrix.hpp
1 #pragma once 2 3 #include <iostream> 4 #include <cassert> 5 6 using std::cout; 7 using std::endl; 8 9 // 类Matrix的声明 10 class Matrix { 11 public: 12 Matrix(int n, int m); // 构造函数，构造一个n*m的矩阵, 初始值为value 13 Matrix(int n); // 构造函数，构造一个n*n的矩阵, 初始值为value 14 Matrix(const Matrix& x); // 复制构造函数， 使用已有的矩阵X构造 15 ~Matrix(); 16 17 void set(const double* pvalue); // 用pvalue指向的连续内存块数据按行为矩阵赋值 18 void clear(); // 把矩阵对象的值置0 19 20 const double& at(int i, int j) const; // 返回矩阵对象索引(i,j)的元素const引用 21 double& at(int i, int j); // 返回矩阵对象索引(i,j)的元素引用 22 23 int get_lines() const; // 返回矩阵对象行数 24 int get_cols() const; // 返回矩阵对象列数 25 26 void display() const; // 按行显示矩阵对象元素值 27 28 private: 29 int lines; // 矩阵对象内元素行数 30 int cols; // 矩阵对象内元素列数 31 double* ptr; 32 }; 33 34 // 类Matrix的实现：matrix.cpp
matrix.cpp
1 #include<iostream> 2 #include<cassert> 3 #include"matrix.hpp" 4 5 int value = 0; 6 Matrix::Matrix(int n, int m) :lines{ n }, cols{ m } 7 { 8 ptr = new double[m * n]; 9 double* p = ptr; 10 for (int i = 0; i < m * n; i++) 11 { 12 *p = value; 13 p++; 14 } 15 } 16 Matrix::Matrix(int n) :lines{ n }, cols{ n } 17 { 18 ptr = new double[n * n]; 19 double* p = ptr; 20 for (int i = 0; i < n * n; i++) 21 { 22 *p = value; 23 p++; 24 } 25 } 26 Matrix::Matrix(const Matrix& x) :lines{ x.lines }, cols{ x.cols } 27 { 28 ptr = new double[x.lines * x.cols]; 29 double* p1 = ptr, * p2 = x.ptr; 30 for (int i = 0; i < x.lines * x.cols; i++) 31 { 32 *p1 = *p2; 33 p1++; 34 p2++; 35 } 36 } 37 void Matrix::set(const double* pvalue) 38 { 39 double* p1 = ptr; 40 const double* p2 = pvalue; 41 for (int i = 0; i < lines * cols; i++) 42 { 43 *p1 = *p2; 44 p1++; 45 p2++; 46 } 47 } 48 Matrix::~Matrix() 49 { 50 delete[] ptr; 51 } 52 void Matrix::clear() 53 { 54 double* p = ptr; 55 for (int i = 0; i < lines * cols; i++) 56 { 57 *p = 0; 58 p++; 59 } 60 } 61 const double& Matrix::at(int i, int j) const 62 { 63 return *(ptr + i * cols + j); 64 } 65 double& Matrix::at(int i, int j) 66 { 67 return *(ptr + i * cols + j); 68 } 69 int Matrix::get_lines() const 70 { 71 return lines; 72 } 73 int Matrix::get_cols() const 74 { 75 return cols; 76 } 77 void Matrix::display() const 78 { 79 for (int i = 0; i < lines; i++) 80 { 81 for (int j = 0; j < cols; j++) 82 { 83 cout << *(ptr + i * cols + j) << " "; 84 } 85 cout << endl; 86 } 87 }
task4.cpp
1 #include "matrix.hpp" 2 #include <iostream> 3 #include <cassert> 4 5 using std::cin; 6 using std::cout; 7 using std::endl; 8 9 10 const int N = 1000; 11 12 // 输出矩阵对象索引为index所在行的所有元素 13 void output(const Matrix& m, int index) { 14 assert(index >= 0 && index < m.get_lines()); 15 16 for (auto j = 0; j < m.get_cols(); ++j) 17 cout << m.at(index, j) << ", "; 18 cout << "\b\b \n"; 19 } 20 21 22 void test1() { 23 double x[1000] = { 1, 3, 5, 7, 9, 11, 13, 15, 17 }; 24 25 int n, m; 26 cout << "Enter n and m: "; 27 cin >> n >> m; 28 29 Matrix m1(n, m); // 创建矩阵对象m1, 大小n×m 30 m1.set(x); // 用一维数组x的值按行为矩阵m1赋值 31 32 Matrix m2(m, n); // 创建矩阵对象m1, 大小m×n 33 m2.set(x); // 用一维数组x的值按行为矩阵m1赋值 34 35 Matrix m3(2); // 创建一个2×2矩阵对象 36 m3.set(x); // 用一维数组x的值按行为矩阵m4赋值 37 38 cout << "矩阵对象m1: \n"; m1.display(); cout << endl; 39 cout << "矩阵对象m2: \n"; m2.display(); cout << endl; 40 cout << "矩阵对象m3: \n"; m3.display(); cout << endl; 41 } 42 43 void test2() { 44 Matrix m1(2, 3); 45 m1.clear(); 46 47 const Matrix m2(m1); 48 m1.at(0, 0) = -999; 49 50 cout << "m1.at(0, 0) = " << m1.at(0, 0) << endl; 51 cout << "m2.at(0, 0) = " << m2.at(0, 0) << endl; 52 cout << "矩阵对象m1第0行: "; output(m1, 0); 53 cout << "矩阵对象m2第0行: "; output(m2, 0); 54 } 55 56 int main() { 57 cout << "测试1: \n"; 58 test1(); 59 60 cout << "测试2: \n"; 61 test2(); 62 }
实验任务五
user.hpp
1 #pragma once 2 #include<iostream> 3 #include<string> 4 using namespace std; 5 6 class User 7 { 8 private: 9 string name, password, email; 10 public: 11 User(string x); 12 User(string x, string y, string z); 13 void set_email(); 14 void change_password(); 15 void display() const; 16 }; 17 User::User(string x) :name{ x } 18 { 19 password = "123456"; 20 email = "\0"; 21 } 22 User::User(string x, string y, string z) :name{ x }, password{ y }, email{ z }{} 23 void User::set_email() 24 { 25 cout << "请输入邮箱："; 26 cin >> email; 27 int t = 1; 28 while(t) 29 { 30 for (char c : email) 31 { 32 if (c == '@') 33 t = 0; 34 } 35 if (t == 0); 36 else 37 { 38 cout << "邮箱格式错误，请再次输入："; 39 cin >> email; 40 } 41 } 42 cout << "邮箱成功创建" << endl; 43 } 44 void User::change_password() 45 { 46 string old; 47 cout << "请输入旧密码："; 48 cin >> old; 49 int i = 2; 50 while (old != password&&i) 51 { 52 cout << "密码输入错误，请重新输入："; 53 cin >> old; 54 i--; 55 } 56 if (i == 0) 57 { 58 cout << "密码输入错误次数过多，请稍后再试"; 59 } 60 else 61 { 62 cout << "请输入新密码"; 63 cin >> password; 64 } 65 } 66 67 void User::display() const 68 { 69 cout << "name: " << name << endl; 70 cout << "pass:"; 71 for (int i = 0; i < password.size(); i++) 72 { 73 cout << "*"; 74 } 75 cout << endl; 76 cout << "email:" << email << endl; 77 }
task5.cpp
1 #include "user.hpp" 2 #include <iostream> 3 #include <vector> 4 #include <string> 5 6 using std::cin; 7 using std::cout; 8 using std::endl; 9 using std::vector; 10 using std::string; 11 12 void test() { 13 vector<User> user_lst; 14 15 User u1("Alice", "2024113", "Alice@hotmail.com"); 16 user_lst.push_back(u1); 17 cout << endl; 18 19 User u2("Bob"); 20 u2.set_email(); 21 u2.change_password(); 22 user_lst.push_back(u2); 23 cout << endl; 24 25 User u3("Hellen"); 26 u3.set_email(); 27 u3.change_password(); 28 user_lst.push_back(u3); 29 cout << endl; 30 31 cout << "There are " << user_lst.size() << " users. they are: " << endl; 32 for (auto& i : user_lst) { 33 i.display(); 34 cout << endl; 35 } 36 } 37 38 int main() { 39 test(); 40 }
实验任务六
1 #pragma once 2 class Date 3 { 4 private: 5 int year; 6 int month; 7 int day; 8 int totalDays; 9 public: 10 Date(int year, int month, int day); 11 int getYear()const { return year; } 12 int getMonth() const { return month; } 13 int getDay()const { return day; } 14 int getMaxDay()const; 15 bool isLeapYear()const 16 { 17 return year % 4 == 0 && year % 100 != 0 || year % 400 == 0; 18 } 19 void show()const; 20 int distance(const Date& date)const 21 { 22 return totalDays - date.totalDays; 23 } 24 };
1 #include"date.h" 2 #include<iostream> 3 #include<cstdlib> 4 5 using namespace std; 6 7 namespace 8 { 9 const int DAYS_BEFORE_MONTH[] = { 0,31,59,90,120,151,181,212,243,273,304,334,365 }; 10 } 11 Date::Date(int year, int month, int day) :year(year), month(month), day(day) 12 { 13 if (day <= 0 || day > getMaxDay()) 14 { 15 cout << "Invalid date: "; 16 show(); 17 cout << endl; 18 exit(1); 19 } 20 int years = year - 1; 21 totalDays = year * 365 + years / 4 - years / 100 + years / 400 + DAYS_BEFORE_MONTH[month - 1] + day; 22 if (isLeapYear() && month > 2) totalDays++; 23 } 24 int Date::getMaxDay()const 25 { 26 if (isLeapYear() && month == 2) 27 return 29; 28 else 29 return DAYS_BEFORE_MONTH[month] - DAYS_BEFORE_MONTH[month - 1]; 30 } 31 void Date::show() const 32 { 33 cout << getYear() << "-" << getMonth() << "-" << getDay(); 34 }
1 #pragma once 2 #include"date.h" 3 #include<string> 4 5 class SavingsAccount 6 { 7 private: 8 std::string id; 9 double balance; 10 double rate; 11 Date lastDate; 12 double accumulation; 13 static double total; 14 void record(const Date& date, double amount, const std::string& desc); 15 16 void error(const std::string& msg)const; 17 18 double accumulate(const Date& date) const 19 { 20 return accumulation + balance * date.distance(lastDate); 21 22 } 23 public: 24 SavingsAccount(const Date& date, const std::string& id, double rate); 25 26 const std::string& getId() const { return id; } 27 double getBalance() const { return balance; } 28 29 double getRate() const { return rate; } 30 31 static double getTotal() { return total; } 32 33 void deposit(const Date& date, double amount, const std::string& desc); 34 35 void withdraw(const Date& date, double amount, const std::string& desc); 36 37 void settle(const Date& date); 38 39 void show() const; 40 };
1 #include "account.h" 2 #include<cmath> 3 #include<iostream> 4 5 using namespace std; 6 7 double SavingsAccount::total = 0; 8 9 SavingsAccount::SavingsAccount(const Date& date, const string& id, double rate) : id(id), balance(0), rate(rate), lastDate(date), accumulation(0) 10 { 11 date.show(); 12 cout << "\t#" << id << " created" << endl; 13 } 14 15 void SavingsAccount::record(const Date& date, double amount, const string& desc) 16 { 17 accumulation = accumulate(date); 18 19 lastDate = date; 20 21 amount = floor(amount * 100 + 0.5) / 100; //保留小数点后两位 22 balance += amount; 23 total += amount; 24 date.show(); 25 26 cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl; 27 28 } 29 void SavingsAccount::error(const string& msg)const 30 { 31 cout << "Error(#" << id << "):" << msg << endl; 32 33 } 34 35 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) 36 { 37 record(date, amount, desc); 38 39 } 40 41 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) 42 { 43 if (amount > getBalance()) 44 error("not enough money"); 45 else 46 record(date, -amount, desc); 47 48 } 49 50 void SavingsAccount::settle(const Date& date) 51 { 52 53 double interest = accumulate(date) * rate / date.distance(Date(date.getYear() - 1, 1, 1)); //计算年息 54 55 if (interest != 0) 56 57 record(date, interest, "interest"); 58 59 accumulation = 0; 60 61 } 62 63 void SavingsAccount::show() const 64 { 65 cout << id << "\tBalance:" << balance; 66 }
1 #include"account.h" 2 #include<iostream> 3 4 using namespace std; 5 6 int main() 7 { 8 Date date(2008, 11, 1); 9 10 SavingsAccount accounts[] = 11 { 12 SavingsAccount(date, "03755217", 0.015), 13 SavingsAccount(date, "02342342", 0.015) 14 }; 15 const int n = sizeof(accounts) / sizeof(SavingsAccount); 16 17 accounts[0].deposit(Date(2008, 11, 5), 5000, "salary"); 18 accounts[1].deposit(Date(2008, 11, 25), 10000, "sell stock 0323"); 19 accounts[0].deposit(Date(2008, 12, 5), 5500, "salary"); 20 accounts[1].withdraw(Date(2008, 12, 20), 4000, "buy a laptop"); 21 22 cout << endl; 23 for (int i = 0; i < n; i++) 24 { 25 accounts[i].settle(Date(2009, 1, 1)); 26 accounts[i].show(); 27 cout << endl; 28 } 29 cout << "Total: " << SavingsAccount::getTotal() << endl; 30 return 0; 31 }
