面向对象程序设计——C++

• 编程专栏
• • C++风格简单题
  • • 百钱问题（1元兑换成1,2,5,分的种类）
    • 引用的例子——排序(从小到大)
  • 类和对象题
  • • 简单的成员函数题
    • 对象数组题
  • 继承与派生类题
  • • 面积题
    • 学生和教师
  • 虚函数题

编程专栏

C++风格简单题

百钱问题（1元兑换成1,2,5,分的种类）

#include <iostream>
using namespace std;
int main()
{
	int i, j, sum = 0;
	for (i = 0; i <= 20; i++)
	{
		for (j = 0; j <= 50; j++)
		{
			if (100 - 5 * i - 2 * j >= 0) {
				sum++;
				cout << "1分：" << (100 - 5 * i - 2 * j) << "\t2分：";
				cout << j << "\t5分：" << i << endl;
			}				
		}
	}
	cout << "sum is "<< sum << endl;
	return 0;
}

引用的例子——排序(从小到大)

#include<iostream>
using namespace std;
int main()
{
	void change(int &, int &);
	int a, b;
	cin >> a >> b;
	if (a > b) change(a, b);
	cout << a <<"  "<< b << endl;
	return 0;
}

void change(int &a1, int &b1)
{
	int t;
	t = a1;
	a1 = b1;
	b1 = t;
}

类和对象题

简单的成员函数题

用类外定义类内成员函数，实现年月日显示。

#include<iostream>
using namespace std;
class Date {
public :
	void print();
	void setday(int d);
	void setmonth(int m);
	void setyear(int y);
private:
	int day, month, year;
};

void Date::print()
{
	cout << "日期为" << year << "年";
	cout << month << "月" << day<<"日"<< endl;
}

void Date::setday(int d)
{
	day = d;
}
void Date::setmonth(int m) {
	month = m;
}
void Date::setyear(int y)
{
	year = y;
}

int main()
{
	Date thisday;
	thisday.setday(3);
	thisday.setmonth(6);
	thisday.setyear(2021);
	thisday.print();
	return 0;
}

对象数组题

构建一个类book,其中含有两个私有数据成员qu和price，将qu初始化为1~5，将price初始化为qu的10倍，建立一个有5个元素的数组元素，显示每个对象数组元素的qu*price值。

#include <iostream>
using namespace std;
class book {
private:
	int qu, price;
public:
	book(int a, int b) {
		qu = a;
		price = b;
	}

	void  show_money()
	{
		cout << qu * price << endl;
	}
};

int main()
{
	book ob[5] = {
		book(1,10),
		book(2,20),
		book(3,30),
		book(4,40),
		book(5,50)
	};
	for (int i = 0; i < 5; i++)
		 ob[i].show_money() ; 
	return 0;
}

继承与派生类题

面积题

建立基类area_cl的两个派生类rectangle与iosceles 让每一个派生类都包含一个函数area ()分别用来返回与三角形的面积。用构造函数对height与width进行初始化。
写出主程序，矩形高10.0 宽5.0，三角形宽长6.0 高4.0;
通过基类访问虚函数的方法即运行时的多态分别求面积

#include<iostream>
using namespace std;
class area_c1{
protected:
	double height;
	double width;
public :
	area_c1(double r, double s)
	{
		area_c1::height = r;
		area_c1::width = s;
	}
	virtual double area() = 0;
};

class rectangle :public area_c1{
public :
	rectangle(double r, double s):area_c1(r, s)
	{}
	double area(){
		return  height * width;
	}
};

class isosceles : public area_c1 {
public :
	isosceles (double r, double s) :area_c1(r, s)
	{}
	double area(){
		return  height * width/2;
	}
};
int main() {
	area_c1 *ob;
	rectangle ob1(10.0, 5.0);
	isosceles ob2(4.0, 6.0);
	ob = &ob1;
	cout<< "矩形面积" << ob->area() << endl;
	ob = &ob2;
	cout << "三角形面积" << ob->area() << endl;
}

学生和教师

编写一个学生和教师数据输入和显示数据程序，学生数据有编号，姓名，班号，成绩，教师有编号，姓名，职称，和部门。要求将编号，姓名输入和显示设计成一个类person ，并作为学生数据操作类 student 和教师数据操作类teacher的基类。

#include <iostream>
using namespace std;
class person {
private:
	int no;
	char name[10];
public :
	
	void shuru()
	{
		cout << "编号"; cin >> no;
		cout << "姓名"; cin >> name;
	}
	void print()
	{
		cout << "编号" << no << endl;
		cout << "姓名" << name << endl;
	}
};

class student : public person {
private:
	int banhao;
	int score;
	
public:	
	void shuru()
	{
		person::shuru();
		cout << "班号"; cin >> banhao;
		cout << "分数"; cin >> score;

	}
	void print()
	{
		person::print();
			cout << "班号" << banhao << endl;
			cout << "分数" << score <<endl;
	}
};

class teacher :public person {
private:
	char zhicheng[10];
	char apart[10];
public :
	void shuru() {
		person::shuru();
		cout << "职称"; cin >> zhicheng;
		cout << "部门"; cin >> apart;
	}

	void print()
	{
		person::print();
		cout << "职称" << zhicheng<< endl;
		cout << "部门" << apart << endl;
	}

};
int main()
{
	student s1;
	teacher t1;
	cout << "输入学生数据" << endl;
	s1.shuru();
	cout << "\n输入老师数据" << endl;
	t1.shuru();
	cout << "\n显示学生数据" << endl;
	s1.print();
	cout << "\n显示老师数据" << endl;
	t1.print();
	return 0;
}

虚函数题

写一个程序，定义抽象基类Container，由它派生出三个派生类：Spere(球体)，Cylinder（圆柱体），Cude (正方体)，用虚函数分别计算几种图形的表面积和体积。

#include <iostream>
using namespace std;
class Container {
protected :
	double radiux;
	double height;

public :
	Container(double ra) {
		Container::radiux = ra;
	}

	double print_ra() {
		return radiux;

	}
	double print_he() {
		return height;
	}
	virtual double s_area() = 0;
	virtual double volume() = 0;
};

class sphere :public Container{
public:
	sphere(double ra) : Container(ra)
	{ }
	double s_area() 
	{
		return 4 * 3.14*radiux* radiux;
	}
	double volume()
	{
		return 3.14*radiux* radiux*radiux*4/3;
	}

};

class cylinder :public Container {
public:
	cylinder(double ra,double he) : Container(ra)
	{
		height = he;
	}
	double s_area()
	{
		return 2 * 3.14*radiux* (radiux+height);
	}
	double volume()
	{
		return  3.14*radiux* radiux*height;
	}

};

class cube :public Container {
public:
   cube(double ra) : Container(ra)
	{ }
	double s_area()
	{
		return 6*radiux* radiux;
	}
	double volume()
	{
		return radiux* radiux*radiux;
	}

};


int main()
{
	Container *ptr;
	sphere obj1(8);
	cylinder obj2(3,5);
	cube obj3(5);
	ptr = &obj1;
	cout << "球的半径为" << ptr->print_ra ()<< endl;
	cout << "球的表面积为" << ptr->s_area ()<< endl;
	cout << "球的体积为" << ptr->volume ()<< endl;
	ptr = &obj2;
	cout << "圆柱的半径为" << ptr->print_ra() << endl;
	cout << "圆柱的高为" << ptr->print_he ()<< endl;
	cout << "圆柱的表面积为" << ptr->s_area() << endl;
	cout << "圆柱的体积为" << ptr->volume() << endl;
	ptr = &obj3;
	cout << "正方体的半径为" << ptr->print_ra() << endl;
	cout << "正方体的表面积为" << ptr->s_area() << endl;
	cout << "正方体的体积为" << ptr->volume() << endl;                    
	return 0;

}