实验3 类和对象_基础编程2

实验任务一

代码

window.hpp

#pragma once
#include "button.hpp"
#include <vector>
#include <iostream>

using std::vector;
using std::cout;
using std::endl;

// ´°¿ÚÀà
class Window{
public:
    Window(const string &win_title);
    void display() const;
    void close();
    void add_button(const string &label);

private:
    string title;
    vector<Button> buttons;
};

Window::Window(const string &win_title): title{win_title} {
    buttons.push_back(Button("close"));
}

inline void Window::display() const {
    string s(40, '*');

    cout << s << endl;
    cout << "window title: " << title << endl;
    cout << "It has " << buttons.size() << " buttons: " << endl;
    for(const auto &i: buttons)
        cout << i.get_label() << " button" << endl;
    cout << s << endl;
}

void Window::close() {
    cout << "close window '" << title << "'" << endl;
    buttons.at(0).click();
}

void Window::add_button(const string &label) {
    buttons.push_back(Button(label));
}

button.hpp

#pragma once

#include <iostream>
#include <string>

using std::string;
using std::cout;

// °´Å¥Àà
class Button {
public:
    Button(const string &text);
    string get_label() const;
    void click();

private:
    string label;
};

Button::Button(const string &text): label{text} {
}

inline string Button::get_label() const {
    return label;
}

void Button::click() {
    cout << "Button '" << label << "' clicked\n";
}

task1.cpp

#include "window.hpp"
#include <iostream>

using std::cout;
using std::cin;

void test() {
    Window w1("new window");
    w1.add_button("maximize");
    w1.display();
    w1.close();
}

int main() {
    cout << "ÓÃ×éºÏÀàÄ£Äâ¼òµ¥GUI:\n";
    test();
}

 

 

 

编译结果

 

问题1: 

自定义了两个类，Button和Window；使用到了std::string和std::vector。；Window类与Button类之间存在组合关系。

问题2: 

const关键字用于那些不修改对象状态的成员函数。Button::get_label被声明为const，因为它仅返回Button的标签而不修改任何成员变量。Window::display同样被声明为const，因为它只是显示窗口和按钮信息而不改变任何状态。；

Button::click可以加const，因为它输出信息但不改变Button的状态

Button::click和Window::add_button等因为包含逻辑较多的操作，不适宜设置为inline。

问题3：定义一个长度为48的类型的字符串，元素都为“*”；

 

实验任务二

代码

 

#include <iostream>
#include <vector>

using namespace std;

void output1(const vector<int> &v) {
    for(auto &i: v)
        cout << i << ", ";
    cout << "\b\b \n";
}

void output2(const vector<vector<int>> v) {
    for(auto &i: v) {
        for(auto &j: i)
            cout << j << ", ";
        cout << "\b\b \n";
    }
}

void test1() {
    vector<int> v1(5, 42);
    const vector<int> v2(v1);

    v1.at(0) = -999;
    cout << "v1: ";  output1(v1);
    cout << "v2: ";  output1(v2);
    cout << "v1.at(0) = " << v1.at(0) << endl;
    cout << "v2.at(0) = " << v2.at(0) << endl;
}

void test2() {
    vector<vector<int>> v1{{1, 2, 3}, {4, 5, 6, 7}};
    const vector<vector<int>> v2(v1);

    v1.at(0).push_back(-999);
    cout << "v1: \n";  output2(v1);
    cout << "v2: \n";  output2(v2);

    vector<int> t1 = v1.at(0);
    cout << t1.at(t1.size()-1) << endl;
    
    const vector<int> t2 = v2.at(0);
    cout << t2.at(t2.size()-1) << endl;
}

int main() {
    cout << "测试1:\n";
    test1();

    cout << "\n测试2:\n";
    test2();
}

 

编译结果

 问题1：

21  vector<int> v1(5, 42); // 创建一个包含5个整数的vector，每个整数初始化为42

22  vector<int> v2(v1);    // 通过复制构造函数创建v2，v2是v1的深拷贝

23  v1.at(0) = -999;       // 通过at成员函数访问v1的第一个元素，并将其值设置为-999

问题2：

32  vector<vector<int>> v1{{1, 2, 3}, {4, 5, 6, 7}}; // 创建一个包含两个vector<int>的vector，第一个有三个元素，第二个有四个元素

33  const vector<vector<int>> v2(v1);                // 通过复制构造函数创建v2，v2是v1的深拷贝

35  v1.at(0).push_back(-999);                        // 访问v1中的第一个vector，并在其末尾添加一个整数-999

问题3：

39  vector<int> t1 = v1.at(0); // 通过复制构造函数，从v1中获取第一个vector的一个拷贝

40  cout << t1.at(t1.size()-1) << endl; // 打印t1中最后一个元素，也就是-999

42  const vector<int> t2 = v2.at(0); // 从v2中获取第一个vector的一个const拷贝

43  cout << t2.at(t2.size()-1) << endl; // 打印t2中最后一个元素，应为3，因为v2是v1复制前的状态的拷贝

问题4：

1.深复制。在第一测试中，v1和v2是独立的；修改v1不影响v2。在第二测试中，修改v1中的一个子vector也不影响v2中相应的子vector，说明v2是v1的完全独立拷贝。

2.至少需要提供一个const成员函数作为接口。

 

 实验任务3

代码

task3.cpp

#include "vectorInt.hpp"
#include <iostream>

using std::cin;
using std::cout;

void output(const vectorInt &vi) {
    for(auto i = 0; i < vi.get_size(); ++i)
        cout << vi.at(i) << ", ";
    cout << "\b\b \n";
}


void test1() {
    int n;
    cout << "Enter n: ";
    cin >> n;

    vectorInt x1(n);
    for(auto i = 0; i < n; ++i)
        x1.at(i) = i*i;
    cout << "x1: ";  output(x1);

    vectorInt x2(n, 42);
    vectorInt x3(x2);
    x2.at(0) = -999;
    cout << "x2: ";  output(x2);
    cout << "x3: ";  output(x3);
}

void test2() {
    const vectorInt  x(5, 42);
    vectorInt y(10, 0);

    cout << "y: ";  output(y);
    y.assign(x);
    cout << "y: ";  output(y);
    
    cout << "x.at(0) = " << x.at(0) << endl;
    cout << "y.at(0) = " << y.at(0) << endl;
}

int main() {
    cout << "测试1: \n";
    test1();

    cout << "\n测试2: \n";
    test2();
}

vectorInt.hpp

#pragma once

#include <iostream>
#include <cassert>

using std::cout;
using std::endl;

class vectorInt{
public:
    vectorInt(int n);
    vectorInt(int n, int value);
    vectorInt(const vectorInt &vi);
    ~vectorInt();

    int& at(int index);
    const int& at(int index) const;

    vectorInt& assign(const vectorInt &v);
    int get_size() const;

private:
    int size;
    int *ptr;     
};

vectorInt::vectorInt(int n): size{n}, ptr{new int[size]} {
}

vectorInt::vectorInt(int n, int value): size{n}, ptr{new int[size]} {
    for(auto i = 0; i < size; ++i)
        ptr[i] = value;
}

vectorInt::vectorInt(const vectorInt &vi): size{vi.size}, ptr{new int[size]} {
    for(auto i = 0; i < size; ++i)
        ptr[i] = vi.ptr[i];
}

vectorInt::~vectorInt() {
    delete [] ptr;
}

const int& vectorInt::at(int index) const {
    assert(index >= 0 && index < size);

    return ptr[index];
}

int& vectorInt::at(int index) {
    assert(index >= 0 && index < size);

    return ptr[index];
}

vectorInt& vectorInt::assign(const vectorInt &v) {  
    delete[] ptr;     

    size = v.size;
    ptr = new int[size];

    for(int i = 0; i < size; ++i)
        ptr[i] = v.ptr[i];

    return *this;
}

int vectorInt::get_size() const {
    return size;
}

 

编译结果

 

问题：

问题1：

是深复制。

问题2：

测试代码将无法正常工作，尤其是所有想通过 at() 修改数组中元素的地方都会出现错误。

const 成员函数的目的是保证函数调用不会修改类的内部状态，包括其成员变量。去掉 const 会导致 const vectorInt 对象无法调用该方法，因为它会破坏常量对象的不可变性。所以这种情况下会存在潜在的安全隐患，因为违反了常量对象的访问规则，可能会导致不可预测的行为。

问题3：

如果将返回类型改为 vectorInt，则会返回一个新的对象副本，而不是对原对象本身的引用，这样的话链式操作将无法进行，因为每次调用都会产生一个新的对象而不是对当前对象的引用。此外，频繁创建新的对象也会导致不必要的内存分配，降低程序的效率。因此，将返回类型改为 vectorInt 会导致 无法实现链式调用，且增加不必要的性能开销，因此不是合适的选择。

 

实验任务4

代码

matrix.hpp

#pragma once
#include <iostream>
#include <cassert>

using std::cout;
using std::endl;

// 类Matrix的声明和实现
class Matrix {
public:
    Matrix(int n, int m); // 构造函数，构造一个n*m的矩阵
    Matrix(int n); // 构造函数，构造一个n*n的矩阵
    Matrix(const Matrix &x); // 复制构造函数， 使用已有的矩阵X构造
    ~Matrix(); // 析构函数
    void set(const double *pvalue); // 用pvalue指向的连续内存块数据按行赋值
    void clear(); // 把矩阵对象的值置0
    const double& at(int i, int j) const; // 返回矩阵对象索引(i, j)的元素 const 引用
    double& at(int i, int j); // 返回矩阵对象索引(i, j)的元素引用
    int get_lines() const; // 返回矩阵对象行数
    int get_cols() const; // 返回矩阵对象列数
    void display() const; // 按行显示矩阵对象元素值

private:
    int lines; // 矩阵对象内元素行数
    int cols; // 矩阵对象内元素列数
    double *ptr; // 指向动态分配的二维矩阵内存块
};

// 构造一个n*m的矩阵
Matrix::Matrix(int n, int m) : lines{n}, cols{m}, ptr{new double[n * m]} {
    for (int i = 0; i < lines * cols; ++i) {
        ptr[i] = 0.0;
    }
}

// 构造一个n*n的矩阵
Matrix::Matrix(int n) : Matrix(n, n) {}

// 复制构造函数，实现深复制
Matrix::Matrix(const Matrix &x) : lines{x.lines}, cols{x.cols}, ptr{new double[x.lines * x.cols]} {
    for (int i = 0; i < lines * cols; ++i) {
        ptr[i] = x.ptr[i];
    }
}

// 析构函数，释放动态内存
Matrix::~Matrix() {
    delete[] ptr;
}

// 用pvalue指向的连续内存块数据按行赋值
void Matrix::set(const double *pvalue) {
    for (int i = 0; i < lines * cols; ++i) {
        ptr[i] = pvalue[i];
    }
}

// 把矩阵对象的值置0
void Matrix::clear() {
    for (int i = 0; i < lines * cols; ++i) {
        ptr[i] = 0.0;
    }
}

// 返回矩阵对象索引(i, j)的元素的const引用
const double& Matrix::at(int i, int j) const {
    assert(i >= 0 && i < lines);
    assert(j >= 0 && j < cols);
    return ptr[i * cols + j];
}

// 返回矩阵对象索引(i, j)的元素引用
double& Matrix::at(int i, int j) {
    assert(i >= 0 && i < lines);
    assert(j >= 0 && j < cols);
    return ptr[i * cols + j];
}

// 返回矩阵对象的行数
int Matrix::get_lines() const {
    return lines;
}

// 返回矩阵对象的列数
int Matrix::get_cols() const {
    return cols;
}

// 按行显示矩阵对象元素值
void Matrix::display() const {
    for (int i = 0; i < lines; ++i) {
        for (int j = 0; j < cols; ++j) {
            cout << at(i, j) << " ";
        }
        cout << endl;
    }
}

task4.cpp

#include "matrix.hpp"
#include <iostream>
#include <cassert>

using std::cin;
using std::cout;
using std::endl;


const int N = 1000;

// 输出矩阵对象索引为index所在行的所有元素
void output(const Matrix &m, int index) {
    assert(index >= 0 && index < m.get_lines());

    for(auto j = 0; j < m.get_cols(); ++j)
        cout << m.at(index, j) << ", ";
    cout << "\b\b \n";
}


void test1() {
    double x[1000] = {12, 23, 34, 45, 56, 67, 78, 89, 91};

    int n, m;
    cout << "Enter n and m: ";
    cin >> n >> m;

    Matrix m1(n, m);    // 创建矩阵对象m1, 大小n×m
    m1.set(x);          // 用一维数组x的值按行为矩阵m1赋值

    Matrix m2(m, n);    // 创建矩阵对象m1, 大小m×n
    m2.set(x);          // 用一维数组x的值按行为矩阵m1赋值

    Matrix m3(2);       // 创建一个2×2矩阵对象
    m3.set(x);          // 用一维数组x的值按行为矩阵m4赋值

    cout << "矩阵对象m1: \n";   m1.display();  cout << endl;
    cout << "矩阵对象m2: \n";   m2.display();  cout << endl;
    cout << "矩阵对象m3: \n";   m3.display();  cout << endl;
}

void test2() {
    Matrix m1(2, 3);
    m1.clear();
    
    const Matrix m2(m1);
    m1.at(0, 0) = -999;

    cout << "m1.at(0, 0) = " << m1.at(0, 0) << endl;
    cout << "m2.at(0, 0) = " << m2.at(0, 0) << endl;
    cout << "矩阵对象m1第0行: "; output(m1, 0);
    cout << "矩阵对象m2第0行: "; output(m2, 0);
}

int main() {
    cout << "测试1: \n";
    test1();

    cout << "测试2: \n";
    test2();
}

编译结果

 

 

实验任务5

代码

task5.cpp

#include "user.hpp"
#include <iostream>
#include <vector>
#include <string>

using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::string;

void test() {
    vector<User> user_lst;

    User u1("Alice", "2024113", "Alice@hotmail.com");
    user_lst.push_back(u1);
    cout << endl;

    User u2("Bob");
    u2.set_email();
    u2.change_password();
    user_lst.push_back(u2);
    cout << endl;

    User u3("Hellen");
    u3.set_email();
    u3.change_password();
    user_lst.push_back(u3);
    cout << endl;

    cout << "There are " << user_lst.size() << " users. they are: " << endl;
    for(auto &i: user_lst) {
        i.display();
        cout << endl;
    }
}

int main() {
    test();
}

user.hpp

#pragma once
#include <iostream>
#include <string>
#include <cassert>

using std::cin;
using std::cout;
using std::endl;
using std::string;

class User {
public:
    User(const string& name, const string& password = "123456", const string& email = "")
        : name{name}, password{password}, email{email} {}

    void set_email() {
        while (true) {
            cout << "Enter email address: ";
            cin >> email;
            if (is_valid_email(email)) {
                cout << "email is set successfully...\n";
                break;
            } else {
                cout << "illegal email. Please re-enter email: ";
            }
        }
    }

    // 修改密码
    void change_password() {
        string old_password;
        int attempts = 0;
        while (attempts < 3) {
            cout << "Enter old password: ";
            cin >> old_password;
            if (old_password == password) {
                string new_password;
                cout << "Enter new password: ";
                cin >> new_password;
                password = new_password;
                cout << "new password is set successfully...\n";
                return;
            } else {
                attempts++;
                if (attempts < 3) {
                    cout << "password input error. Please re-enter again: ";
                } else {
                    cout << "password input error. Please try after a while.\n";
                }
            }
        }
    }

    void display() const {
        cout << "name: " << name << endl;
        cout << "pass: " << string(password.size(), '*') << endl;
        cout << "email: " << email << endl;
    }

private:
    string name;
    string password;
    string email;

    bool is_valid_email(const string& email) const {
        auto pos = email.find("@");
        return pos != string::npos && pos != 0 && pos != email.size() - 1;
    }
};

 

编译结果

 

实验任务6

代码

6 25.cpp

#include"account.h"
#include<iostream>
using namespace std;
int main() {
    Date date(2008, 11, 1);
    SavingsAccount accounts[] = {
        SavingsAccount(date,"03755217",0.015),
        SavingsAccount(date,"02342342",0.015)

    };
    const int n = sizeof(accounts) / sizeof(SavingsAccount);
    accounts[0].deposit(Date(2008, 11, 5), 5000, "salary");
    accounts[1].deposit(Date(2008, 11, 25), 10000, "sell stock 0323");
    accounts[0].deposit(Date(2008, 12, 5), 5500, "salary");
    accounts[1].withdraw(Date(2008, 12, 20), 4000, "buy a laptop");
    cout << endl;
    for (int i = 0; i < n; i++) {
        accounts[i].settle(Date(2009, 1, 1));
        accounts[i].show();
        cout << endl;
    }
    cout << "Total:" << SavingsAccount::getTotal() << endl;
    return 0;
}

account.cpp

#include"account.h"
#include<cmath>
#include<iostream>
using namespace std;
double SavingsAccount::total = 0;
SavingsAccount::SavingsAccount(const Date &date, const string& id, double rate)
    :id(id), balance(0), rate(rate), lastDate(date), accumulation(0) {
    date.show();
    cout << "\t#" << id << "created" << endl;

}
void SavingsAccount::record(const Date& date, double amount, const string& desc) {
    accumulation = accumulate(date);
    lastDate = date;
    amount = floor(amount * 100 + 0.5) / 100;
    balance -= amount;
    total += amount;
    date.show();
    cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl;

}
void SavingsAccount::error(const string& msg)const {
    cout << "Error(#" << id << "):" << msg << endl;
}
void SavingsAccount::deposit(const Date &date, double  amount, const string& desc){
    record(date,amount,desc);
    }
    void SavingsAccount::withdraw(const Date& date, double amount, const string& desc){
        if (amount > getBalance())
        error("not enough money");
        else
            record(date,-amount,desc);

    }
        void SavingsAccount::settle(const Date& date) {
    double interest = accumulate(date) * rate
        / date.distance(Date(date.getYear() - 1, 1, 1));
    if (interest != 0)
        record(date, interest, "interest");
    accumulation=0;

}
void SavingsAccount::show()const {
    cout << id << "\tBalance:" << balance;
}

account.h

#ifndef _ _ACCOUNT_H_ _
#define _ _ACCOUNT_H_ _
#include"date.h"
#include<string>
class SavingsAccount {
private:
    std::string id;
    double balance;
    double rate;
    Date lastDate;
    double accumulation;
    static double total;
void record(const Date& date, double amount, const std::string& desc);
void error(const std::string& msg) const;
double accumulate(const Date& date)const {
    return accumulation + balance * date.distance(lastDate);

}
public:
    SavingsAccount(const Date& date, const std::string& id, double rate);
    const std::string& getId()const { return id;}
    double getBalance()const { return balance; }
    double getRate()const { return rate; }
    static double getTotal() { return total; }
    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_ _

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();
}

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;
    }
};

 

编译结果