20250807C++课堂

## 一、C++入门
http://docs.chuangke.tech/doc/88/

## 二、C++初级
课程名称：[C++] 简单图形的打印
课程目标：
1.打印矩形
2.打印直角三角形
3.打印倒直角三角形
4.打印侧等腰三角形
5.打印空心矩形
http://docs.chuangke.tech/doc/129/

## 三、C++高级

```
//****************************
//第五章  特殊函数和成员
//****************************
```
### 5.1分析下面程序中析构函数与构造函数的调用顺序*/
```
#include <iostream>
using namespace std;
class object
{
private:
	int val;
public:
	object():val(0)
	{
		cout<<"Defalt constructor for object"<<endl;
	}
	object(int i):val(i)
	{
		cout<<"Consructor for object"<<val<<endl;
	}
	~object()
	{
		cout<<"Destructor for object"<<val<<endl;
	};
	class container
	{
	private:
		object one;
		object two;
		int data;
	public:
		container():data(0)
		{
			cout<<"Defalt constructor for object"<<endl;
		}
		container(int i,int j,int k);
		~container()
		{
			cout<<"Consructor for object"<<data<<endl;
		};
		container()::container(int i,int j,int k):two(i),one(j)
		{
			data=k;
			cout<<"Constructor for container"<<data<<endl;
		}
		void main()
		{
			constainer obj, anObj(5,6,10);
		}

```
### /*5.2分析下面程序的输出结果*/
```
class Test
{
	static int x;
	int n;
public:
	Test()
	{
	}
	Test(int a,int b)
	{
		x=a;
		n=b;
	}
	static int func()
	{
		return x;
	}
	static void sfunc(Test&r,int a)
	{
		r.n=a;
	}
	int Getn()
	{
		return n;
	}
};
int Test::x=25;
#include <iostream>
using namespace std;
void main()
{
	cout<<Test::func();
	Test b,c;
	b.sfunc(b,58);
	cout<<" "<<b.Getn();
	cout<<" "<<b.func();
	cout<<" "<<c.func();
	Test a(24,56);
	cout<<" "<<a.func()<<" "<<b.func()<<" "<<c.func()<<endl;
}

```
### /*5.3使用表态对象的例子*/
```
#include <iostream>
using namespace std;
class test
{
private:
	int n;
public:
	test(int i)
	{
		n=i;
		cout<<"constructor:"<<i<<endl;
	}
	~test()
	{
		cout<<"destructor:"<<n<<endl;
	}
	int getn()
	{
		return n;
	}
	void inc()
	{
		++n;
	}
};
void main()
{
	cout<<"loop start:"<<endl;
	for(int i=0;i<3;i++)
	{
		static test a(3);
		test b(3);
		a.inc();
		b.inc();
		cout<<"a.n="<<a.getn()<<endl;
		cout<<"b.n="<<b.getn()<<endl;
	}
		cout<<"loop end."<<endl;
		cout<<"Exit main()"<<endl;
}

```
### /*5.4使用友元函数计算两点之间距离的例子*/
```
#include <iostream>
#include <cmath>
using namespace std;
class Point
{
private:
	double X,Y;
public:
	Point(double xi,double yi)
	{
		X=xi;
		Y=yi;
	}
	double GetX()
	{
		return X;
	}
	double GetY()
	{
		return Y;
	}
	friend double distances(Point&,Point&);
};
double distances(Point&a,Point&b)
{
	double dx=a.X-b.X;
	double dy=a.Y-b.Y;
	return sqrt(dx*dx+dy*dy);
}
void main()
{
	Point p1(3.5,5.5),p2(4.5,6.5);
	cout<<"The distance is"<<distances(p1,p2)<<endl;
}

```
### /*5.5类One的对象通过友元函数访问类TWO的对象的私有数据*/
```
#include <iostream>
using namespace std;
class Two;
class One
{
private:
	int x;
public:
	One(int a)
	{
		x=a;
	}
	int Getx()
	{
		return x;
	}
	void func( Two&);
};
class Two
{
private:
	int y;
public:
	Two(int b)
	{
		y=b;
	}
	int Gety()
	{
		return y;
	}
	friend void One::func( Two&);
};
void One::func( Two& r)
{
	r.y=x;
}
void main()
{
	One Obj1(5);
	Two Obj2(8);
	cout<<Obj1.Getx()<<" "<<Obj2.Gety()<<endl;
	Obj1.func(Obj2);
	cout<<Obj1.Getx()<<" "<<Obj2.Gety()<<endl;
}

```
### /*5.6*/
```cpp
#include <iostream>
using namespace std;
class Two
{
	int y;

public:

friend class One;
};
class One
{
	int x;
public:
	One(int a,Two&r,int b)
	{
		x=a;
		r.y=b;
	}
	
	void Display( Two&);
};

void One::Display( Two& r)
{
	cout<<x<<" "<<r.y<<endl;
}
void main()
{
	Two Obj2;
	One Obj1(23,Obj2,55);
	Obj1.Display(Obj2);
}

```
### /*5.7常数据成员初始化和常引用作为函数参数*/
```cpp
#include <iostream>
using namespace std;
class Base
{
private:
	int x;
	const int a;
	static const int b;
	const int& r;
public:
	Base(int ,int);
	void Show()
	{
		cout<<x<<","<<a<<","<<b<<","<<r<<endl;
	}
	void Display(const double &r)
	{
		cout<<r<<endl;
	}
};
const int Base::b=125;
 Base::Base(int i,int j):x(i),a(j),r(x)
{

}
void main()
{
	Base a1(104,118),a2(119,140);
	a1.Show();
	a2.Show();
	a2.Display(3.14159);
}

```
### /*5.8const对象调用const成员函数*/
```cpp
#include <iostream>
using namespace std;
class Base
{
private:
	double x,y;
	const double p;
public:
	Base(double m,double n,double d):p(d)
	{
		x=m;
		y=n;
	}
	void Show();
	void Show()const;
};
void Base::Show()
{
	cout<<x<<","<<y<<" p="<<p<<endl;
}
void Base::Show()const
{
	cout<<x<<","<<y<<" const p="<<p<<endl;
}
void main()
{
	Base a(8.9,2.5,3.1416);
	const Base b(2.5,8.9,3.14);
	b.Show();
	a.Show();
}

```
### /*5.9const函数返回的常数对象与其他常量对象一起使用*/
```cpp
#include <iostream>
using namespace std;
class ConstFun
{
public:
	int f5()const
	{
		return 5;
	}
	int Obj()
	{
		return 45;
	}
};
void main()
{
	ConstFun s;
	const int i=s.f5();
	const int j=s.Obj();
	int x=s.Obj();
	int y=s.f5();
	cout<<i<<" "<<j<<" "<<x<<" "<<y;
	const ConstFun d;
	int k=d.f5();
	cout<<"k="<<k<<endl;
}

```
### /*5.10使用类对象数组和指针的例子*/
```
class Test
{
	int num;
	double f1;
public:
	Test(int n)
	{
		num=n;
	}
	Test(int n,double f)
	{
		num=n;
		f1=f;
	}
	int GetNum()
	{
		return num;
	}
	double GetF()
	{
		return f1;
	}
};
#include <iostream>
using namespace std;
void main()
{
	Test one[2]={2,4},*p;
	Test two[2]={Test(1,3.2),Test(5,9.5)};
	for (int i=0;i<2;i++)
		cout<<"two["<<i<<"]="<<one[i].GetNum()<<endl;
	p=two;
	for(i=0;i<2;i++,p++)
		cout<<"two["<<i<<"]=("<<p->GetNum()<<","<<p->GetF()<<")"<<endl;
}

```
### /*5.11仍然使用类Test，但改用对象指针数组的演示主程序*/
```
#include <iostream>
using namespace std;
void main()
{
	Test *one[2]={new Test(2),new Test(4)};
	Test *two[2]={new Test(1,3.2),new Test(5,9.5)};
	for (int i=0;i<2;i++)
		cout<<"one["<<i<<"]="<<one[i]->GetNum()<<endl;
	for(i=0;i<2;i++)
		cout<<"two["<<i<<"]=("<<p->GetNum()<<","<<p->GetF()<<")"<<endl;
}

```
### /*5.12使用指向类成员函数的指针*/
```
#include <iostream>
using namespace std;
class A
{
private:
	int val;
public:
	A(int i)
	{
		val=i;
	}
	int value(int a)
	{
		return val+a;
	}
};
void main()
{
	int(A::*pfun)(int);
	pfun=A::value;
	A obj(10);
	cout<<(obj.*pfun)(15)<<endl;
	A *pc=&obj;
	cout<<(pc->*pfun)(15)<<endl;
}

/*解一元二次方程*/
/*头文件equation.h*/
#if ! defined(EQUATION_H)
#define EQUATION_H
#include <iostream>
#include <cmath>
using namespace std;
class FindRoot
{
private:
	float a,b,c,d;
	double x1,x2;
public:
	FindRoot(float x,float y,float z);
	void Find();
	void Display();
};
#endif

/*equation.cpp实现类*/
#include "equation.h"
FindRoot::FindRoot(float x,float y,float z)
{
	a=x;
	b=y;
	c=z;
	d=b*b-4*a*c;
}
void FindRoot::Find()
{
	if(d>0)
	{
		x1=(-b+sqrt(d))/(2*a);
    	x2=(-b-sqrt(d))/(2*a);
		return;
	}
else if (d==0)
{
	x1=x2=(-b)/(2*a);
	return;
}
else
{
	x1=(-b)/(2*a);
    x2=sqrt(-d)/(2*a);
}
}
void FindRoot::Display()
{
	if(d>0)
	{
		cout<<"x1="<<x1<<"\nx2="<<x2<<endl;
		return;
	}
	else if (d==0)
	{
		cout<<"x1=x2="<<x1<<endl;
	return;
	}
	else{
		cout<<"x1="<<x1<<"+"<<x2<<"i"<<endl;
		cout<<"x2="<<x1<<"-"<<x2<<"i"<<endl;
	}
}
/*主函数Find.cpp*/
#include "equation.h"
void Read(float&,float&,float&);
void main()
{
	float a,b,c;
	cout<<"这是个一元二次方程AX^2+BX+C=0的根的方程。"<<endl;
	for(;;)
	{
		Read(a,b,c);
		if (a==0)
			return;
		FindRoot obj(a,b,c);
		obj.Find();
		obj.Display();
	}
}
void Read(float& a,float& b,float& c)
{
	cout<<"输入方程系数a:";
	cin>>a;
	if (a==0)
	{
		getchar();
		return;
	}
	cout<<"输入方程系数b:";
	cin>>b;
	cout<<"输入方程系数c:";
	cin>>c;
}
```

## 第四章课后

一、填空题
1.数据成员、成员函数；

2.类、析构函数不允许有参数和返回类型（可是显示地说明参数为void）、一个类有1个析构函数；

3.`fun::fun(fun &)、fun::fun(const fun &);`

二、单项选择题 
1.C。2.C。3.没又答案，应该是`A::~A(void)`、或A::~A()。4.B。 5.C。 6.C。 7.D

三、改错题 
1.return m;---错误，没又定义变量m；

2.A.init(24,56);---错误，没有声明对象A，init函数参数不对应；

Setx函数是int型但是没有返回值

四、完成程序题 
1.
```
#include < iostream >
using namespace std;
class base
{
	private :	//私有数据成员
			int a, b;
	public :
			void init(int x, int y)//公有函数
			{
				a = x;
				b = y;
			}
			void print()
			{
				cout<<"2 * "<< a<<" - "<< b<<" = "<<(2*a-b)<< endl;
			}

};
void main()
{
	base a;
	a.init(68,55);
	a.print();
}
```

2.
```
#include 
using namespace std;
class Point
{
	private : 
			int m, n;
	public :
			Point(int, int);//整型变量，为参数的构造函数
			Point(Point&);//复制构造函数的原型
			print()
			{
				cout<<"m = "<< m<<", n = "<< n<< endl;
			}

};
Point::Point(int a, int b)
{
	m = a;
	n = b;
}
Point::Point(Point & t)//复制构造函数的定义
{
	m = t.m;
	n = t.n;
}
void main()
{
	Point a(10,89);
	Point b(a);
	a.print();
	b.print();
}
```
五、程序分析题

1.没有结果，因为没有main函数
如果加main函数
void main()
{
	base b(10, 20);
}
输出：
初始化...10,20
Destory...10,20

2.
输出：
55

六、编程题

1.设计一个点类Point，再设计一个矩形类，矩形类使用Point类的两个坐标点作为矩形的对角顶点。并可以输出4个坐标值和面积。使用测试程序验证程序。
```
#include < iostream.h >
using namespace std;
class Point	//点类
{
	private:
			int x, y;//私有成员变量，坐标
	public :
			Point()//无参数的构造方法，对xy初始化
			{
				x = 0;
				y = 0;
			}
			Point(int a, int b)//又参数的构造方法，对xy赋值
			{
				x = a;
				y = b;
			}
			void setXY(int a, int b)//设置坐标的函数
			{
				x = a;
				y = b;
			}
			int getX()//得到x的方法
			{
				return x;
			}
			int getY()//得到有的函数
			{
				return y;
			}

};
class Rectangle	//矩形类
{
	private:
			Point point1, point2, point3, point4;//私有成员变量，4个点的对象
	public :
			Rectangle();//类Point的无参构造函数已经对每个对象做初始化啦，这里不用对每个点多初始化了
			Rectangle(Point one, Point two)//用点对象做初始化的，构造函数，1和4为对角顶点
			{
				point1 = one;
				point4 = two;
				init();
			}
			Rectangle(int x1, int y1, int x2, int y2)//用两对坐标做初始化，构造函数，1和4为对角顶点
			{
				point1.setXY(x1, y1);
				point4.setXY(x2, y2);
				init();
			}
			void init()//给另外两个点做初始化的函数
			{
				point2.setXY(point4.getX(), point1.getY() );
				point3.setXY(point1.getX(), point4.getY() );
			}
			void printPoint()//打印四个点的函数
			{
				cout<<"A：("<< point1.getX() <<"，"<< point1.getY() <<")"<< endl;
				cout<<"B：("<< point2.getX() <<"，"<< point2.getY() <<")"<< endl;
				cout<<"C：("<< point3.getX() <<"，"<< point3.getY() <<")"<< endl;
				cout<<"D：("<< point4.getX() <<"，"<< point4.getY() <<")"<< endl;
			}
			int getArea()//计算面积的函数
			{
				int height, width, area;
				height = point1.getY() - point3.getY();
				width = point1.getX() - point2.getX();
				area = height * width;
				if(area > 0)
					return area;
				else
					return -area;
				
			}

};
void main()
{
	Point p1(-15, 56), p2(89, -10);//定义两个点
	Rectangle r1(p1, p2);//用两个点做参数，声明一个矩形对象r1
	Rectangle r2(1, 5, 5, 1);//用两队左边，声明一个矩形对象r2
	
	cout<<"矩形r1的4个定点坐标："<< endl;
	r1.printPoint();
	cout<<"矩形r1的面积："<< r1.getArea() << endl;

cout<<"\n矩形r2的4个定点坐标："<< endl;
	r2.printPoint();
	cout<<"矩形r2的面积："<< r2.getArea() << endl;
}

```
2.使用内联函数设计一个类，用来表示直角坐标系中的任意一条直线并输出它的属性。
```
#include < iostream.h >
#include < math.h >
class Line
{
	private:
			int x1, y1, x2, y2;
	public :
			Line();
			Line(int =0, int =0, int =0, int=0 );
			void printPoint();
			double getLength();
			
};
inline Line::Line(int a, int b, int c, int d)
{
	x1 = a;
	y1 = b;
	x2 = c;
	y2 = d;
}
inline void Line::printPoint()
{
	cout<<"A："<< x1 <<", "<< y1 << endl;
	cout<<"B："<< x2 <<", "<< y2 << endl;
}
inline double Line::getLength()
{
	double length;
	length = sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) );
	return length;
}
void main()
{
	Line line(10,80,-10,12);
	line.printPoint();
	cout<< line.getLength() << endl;

}

```