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 }
View Code
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 }
View Code
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 }
View Code
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 }
View Code
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", "[email protected]");
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 }
View Code
task6:
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 }
View Code
标签：std,const,cout,int,实验,ptr,string From： https://www.cnblogs.com/g055140/p/18525768