task 1

#include<iostream>
#include <string>
#include <vector>
int main()
{    
    using namespace std;
    string s1;
    string s2{"c plus plus"};
    string s3{s2};
    string s4=s2;
    s1 = "oop";
    vector<string> v1; 
    v1.push_back(s1); 
    v1.push_back(s2 + "1");
    v1.push_back(s3 + "2");
    v1.push_back(s4 + "3");
    cout << "output1: " << endl;
    for(auto item: v1)
    cout << item << endl;
    
    cout << "ouput2: ";
    for(auto p = v1.begin(); p != v1.end(); ++p)
    cout << *p << endl;
    
    cout << "output3: " << endl;
    for(auto i = 0; i < v1.size(); ++i)
    cout << v1[i] << endl;
    vector<string> v2{v1.rbegin(), v1.rend()};
    cout << "v2: " << endl;
    for(auto item: v2)
    cout << item << endl;
}

#include <iostream> 
#include <string>
#include <vector> 
#include <cmath> 
#include <cstdlib> 
#include <time.h>
template<typename T>
void output(const T& obj)
{
    for (auto item : obj)
        std::cout << item << " ";
    std::cout << std::endl;
}
int main()
{
    using namespace std;
    vector<int> v1{ 1, 9, 8, 4 };
    v1.insert(v1.begin(), 2022);
    v1.insert(v1.end(), 2023);

    cout << "v1: ";
    output(v1);

    v1.pop_back();
    v1.erase(v1.begin());
    cout << "v1: ";
    output(v1);

    vector<string> v2{ "《1984》", "《动物农场》", "《美丽新世界》" };
    cout << "v2: ";
    output(v2);
}

#include <iostream>
using std::cout;
using std::endl;
class Point
 {
public:
  Point(int x0 = 0, int y0 = 0);
  Point(const Point&p );
  ~Point() = default;
  int get_x() const { return x; } 
  int get_y() const { return y; } 
  void show() const;
private:
  int x, y;
};
Point::Point(int x0, int y0): x{x0}, y{y0}
{
    cout << "constructor called." << endl;
}
Point::Point(const Point& p): x{p.x}, y{p.y}
{
cout << "copy constructor called." << endl;
}
void Point::show() const 
{
cout << "(" << x << ", "<< y << ")" << endl;
}
int main() 
{
    Point p1(4, 5);
    p1.show();
    
    Point p2 = p1;
    p2.show();
    
    Point p3{p2};
    p3.show();
    cout << p3.get_x() << endl;
}

#include <iostream>
#include <iomanip>

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

class Clock
{
public:
    Clock(int h = 0, int m = 0, int s = 0);
    Clock(const Clock& t);
    ~Clock() = default;

    void set_time(int h, int m = 0, int s = 0);
    void show_time() const;

private:
    int hour, minute, second;
};
Clock::Clock(int h, int m, int s) : hour{ h }, minute{ m }, second{ s }
{
    cout << "constructor called" << endl;
}
Clock::Clock(const Clock& t) : hour{ t.hour }, minute{ t.minute },
second{ t.second }
{
    cout << "copy constructor called" << endl;
}
void Clock::set_time(int h, int m, int s)
{
    hour = h;
    minute = m;
    second = s;
}
void Clock::show_time() const
{
    using std::setw;
    using std::setfill;
    cout << setfill('0') << setw(2) << hour << ":"
        << setw(2) << minute << ":"
        << setw(2) << second << endl;
}
Clock reset() {
    return Clock(0, 0, 0);
}
int main()
{
    Clock c1(12, 0, 5);
    c1.show_time();

    c1 = reset();
    c1.show_time();
     
    Clock c2(c1);
    c2.set_time(6);
    c2.show_time();
}

#include <iostream>
class X {
public:
    X();
    ~X();
    X(int m);
    X(const X& obj);
    X(X&& obj) noexcept;
    void show() const;
private:
    int data;
};
X::X() : data{ 42 }
{
    std::cout << "default constructor called.\n";
}
X::~X()
{
    std::cout << "destructor called.\n";
}
X::X(int m) : data(m)
{
    std::cout << "constructor called.\n";
}
X::X(const X& obj) : data{ obj.data }
{
    std::cout << "copy constructor called.\n";
}
X::X(X&& obj) noexcept : data{ obj.data }
{
    std::cout << "move constructor called.\n";
}
void X::show() const
{
    std::cout << data << std::endl;
}
int main()
{
    X x1;
    x1.show();

    X x2{ 2049 };
    x2.show();

    X x3{ x1 };
    x3.show();

    X x4{ std::move(x2) };
    x4.show();
}

#include<iostream>
#include<iomanip>
class Rectangle {
public:
    Rectangle(double length = 2.0, double width = 1.0);
        ~Rectangle() = default;
    Rectangle(const Rectangle& rect);
    double len() { return length; };
    double wide() { return width; };
    double area() { return length * width; };
    double circumference() { return(width + length) * 2; };
    void resize(int times);
    void resize(int times_l, int time_w);
private:
    double length, width;
};
Rectangle::Rectangle(double l, double w) :length(l), width(w) {};
Rectangle::Rectangle(const Rectangle& r) :length(r.length), width(r.width) {};
void Rectangle::resize(int times) { length *= times; width *= times; };
void Rectangle::resize(int times_l, int time_w) { length *= times_l; width *= time_w; };
void output(Rectangle& rect) {
    using namespace std;
         cout << "矩形信息: \n";
         cout << fixed << setprecision(2);
         cout << "长：    " << rect.len() << endl;
         cout << "宽：    " << rect.wide() << endl;
         cout<< "面积：  " << rect.area() << endl;
         cout << "周长：  " << rect.circumference() << endl;
    
        
}
int main()
{
    Rectangle rect1;
    output(rect1);

    Rectangle rect2(10, 5);
    output(rect2);
     
    Rectangle rect3(rect1);
    rect3.resize(2);
    output(rect3);

    rect3.resize(5, 2);
    output(rect3);
  }