一次C++作业

• 综合改错（老师发的题目排版可能有问题）：

#include <iostream>
#include<stdlib.h>
class CComplex
{
public:
	CComplex(double r = 0, double i = 0)
	{
		real = r;
		imag = i;
	}
	int operator int()
	{
		return (int)real;
	}
	void Display(void)
	{
		cout << "(" << real << "," << imag << ")" << endl;
	}
protected:
	double real;
	double imag;
};
class CVector
{
public:
	CVector(CComplex& obj1, CComplex& obj2, CComplex& obj3, CComplex& obj4)
	{
		objArray[0] = obj1;
		objArray[1] = obj2;
		objArray[2] = obj3;
		objArray[3] = obj4;
	}
	friend CComplex& operator[](CVector obj, int n);
private:
	CComplex objArray[4];
};
CComplex& operator[](CVector obj, int n)
{
	if (n < 0 || n>3)
	{
		cout << "Out of range!" << endl;
		exit(0);
	}
	return obj.objArray[n];
}

void main()
{
	CComplex c1(1.1, 1.1);
	CComplex c2(2.2, 2.2);
	CComplex c3(3.3, 3.3);
	CComplex c4(4.4, 4.4);

	CVector v(c1, c2, c3, c4);

	v[0].Display();
	v[1].Display();
	v[2].Display();
	v[3].Display();

	v[0] = 5.5;//1
	v[1] = CComplex(6.6);//2
	v[2] = int(CComplex(7.7));//3
	v[3] = int(CComplex(8.8, 9.9));//4

	v[0] = Display();
	v[1] = Display();
	v[2] = Display();
	v[3] = Display();

}

问题一：上述程序存在两大错误，在不修改主函数和程序原意的前提下，改正该程序中存在的错误。
改正后代码：

#include <iostream>
#include"stdlib.h"
using namespace std;//std流运算符
class CComplex
{
public:
	CComplex(double r = 0, double i = 0)
	{
		real = r;
		imag = i;
	}
	operator int()		//第一大错误：删除第一个int，operator用于类型转换函数时：类型转换函数由operator（前置）修饰，函数名称为目标类型名
	{
		return (int) real;
	}
	void Display(void)
	{
		cout << "(" << real << "," << imag << ")" << endl;
	}
protected:
	double real;
	double imag;
};

class CVector
{
public:
	CVector(CComplex& obj1, CComplex& obj2, CComplex& obj3, CComplex& obj4)
	{
		objArray[0] = obj1;
		objArray[1] = obj2;
		objArray[2] = obj3;
		objArray[3] = obj4;
	}
	//原，删去friend CComplex& operator[](CVector obj, int n);
	CComplex & operator [] (int n);//下标运算符[]是一个双目运算符，只能重载为成员函数，删去形参定义部分及friend关键字
private:
	CComplex objArray[4];
};
//原，删去CComplex & operator [](CVector obj, int n)
CComplex & CVector::operator[](int n)//第二大错误：下标运算符[]是一个双目运算符，只能重载为成员函数，对应的运算符重载函数形式为: type1 & operator[](type2)
									//其中，type1为数组类型，type2为下标类型。
									//C++预定义对type1没有限制，但要求type2必须是int型，数组需要先声明后使用，若type2是其它类型，就需要对下标运算符重载。
{
	if (n < 0 || n>3)
	{
		cout << "Out of range!" << endl;
		exit(0);
	}
	return objArray[n];//删除obj.
}

int main()//main的返回类型应为int而非void
{
	CComplex c1(1.1, 1.1);
	CComplex c2(2.2, 2.2);
	CComplex c3(3.3, 3.3);
	CComplex c4(4.4, 4.4);

	CVector v(c1, c2, c3, c4);

	v[0].Display();
	v[1].Display();
	v[2].Display();
	v[3].Display();

	v[0] = 5.5;
	v[1] = CComplex(6.6);
	v[2] = int(CComplex(7.7));
	v[3] = int(CComplex(8.8, 9.9));

	v[0] .Display();
	v[1] . Display();
	v[2] . Display();
	v[3] . Display();

}

问题二：①处的转换属于显式转换还是隐式转换，并解释该转换过程。
隐式转换…
问题三：②处的转换属于显式转换还是隐式转换，并解释该转换过程。
显式转换…
问题四：解释③处的转换过程。
问题五：解释④处的转换过程。

• 编写一个程序计算三角形、正方形和圆形的面积，要求抽象出一个基类base，在其中说明一个虚函数，用来求面积，并利用单接口，多实现版本设计各图形面积的方法。

#include <iostream>
using namespace std;

class base
{
	virtual void area() = 0;//虚函数
};
class triangle :public base
{
public:
	triangle()
	{
		cout << "请输入三角形的底" << endl;
		cin >> hemline;
		cout << "请输入三角形的高" << endl;
		cin >> height;
	}
	void area()
	{
		cout << "三角形的面积是" << hemline * height / 2 << endl;
	}
private:
	double hemline;
	double height;
};
class square :public base
{
public:
	square()
	{
		cout << "请输入正方形的边长" << endl;
		cin >> length;
	}
	void area()
	{
		cout << "正方形的面积是" << length * length / 2 << endl;
	}
private:
	double length;
};
class circular:public base
{
public:
	circular()
	{
		cout << "请输入圆形的半径"<<endl;
		cin >> radius;
		cout << "请输入pi的值" << endl;
		cin >> pi;
	}
	void area()
	{
		cout << "圆形的面积是" << radius * radius * pi;
	}
private:
	double radius;
	double pi;
};

int main()
{
	triangle tri;
	tri.area();
	square squ;
	squ.area();
	circular cir;
	cir.area();

}

• 设计一个汽车类Motor，该类具有可载人数、轮胎数、马力数、生产厂家和车主五个数据成员，根据Motor类派生出Car类、Bus类和Truck类。其中Bus类除继承基类的数据成员外，还具有表示车厢节数的数据成员Number；Truck类除继承基类的数据成员之外，还具有表示载重量的数据成员Weight。每个类都具有成员函数Display，用于输出各类对象的相关信息。要求设计一个统一的显示相关信息的全局函数ShowInfo在主函数中调用，主函数中不直接调用类里面的Display函数。

#include<iostream>
#include<string>
using namespace std;
class Motor
{
public:
	Motor(int pas , int wheel , int push1 , string madeby1, string owner1) { passengers = pas, wheels = wheel, pushs = push1, madeby = madeby1, owner = owner1; }
	virtual void Display()//void Display()
	{
		cout << "可载人数是" << passengers << "人" << endl;
		cout << "轮胎数是" << wheels << "个" << endl;
		cout << "马力数是" << pushs << endl;
		cout << "生产厂家是" << madeby << endl;
		cout << "车主是" << owner << endl;
		cout << endl;
	}
protected:
	int passengers;
	int wheels;
	int pushs;
	string madeby;
	string owner;
};

class Car :public Motor
{
public:

	Car(int pas, int wheel, int push1, string madeby1, string owner1) :Motor(pas, wheel, push1, madeby1, owner1)
	{
		passengers = pas, wheels = wheel, pushs = push1, madeby = madeby1, owner = owner1;
	}
	void Display()
	{
		Motor::Display();
		cout << endl;
	}
private:
	int passengers;
	int wheels;
	int pushs;
	string madeby;
	string owner;
};

class Bus :public Motor
{
public:
	Bus(int pas, int wheel, int push1, string madeby1, string owner1,int num) :Motor(pas, wheel, push1, madeby1, owner1)
	{
		Number = num;
	}
	void Display()
	{
		cout << "Bus的车厢节数是" << Number << endl;
		Motor::Display();
	}
private:
	int Number;
};

class Truck :public Motor
{
public:
	Truck(int pas, int wheel, int push1, string madeby1, string owner1, double wei) : Motor(pas, wheel, push1, madeby1, owner1)
	{
		Weight = wei;
	}
	void Display()
	{
		cout << "Truck的载重量是" << Weight << endl;
		Motor::Display();
	}
private:
	double Weight;
};
/*int main()
{
	Motor motor1(50, 30, 20, "afib", "sfbisbug");
	motor1.Display();
	Car car1(50, 30, 20, "afib", "sfbisbug");
	car1.Display();

	Bus bus1(40, 20, 10, "afiubf", "abfb", 50);
	bus1.Display();
	Truck truck1(10, 20, 30, "afigf", "afnkb", 20.0);
	truck1.Display();
}*/
void ShowInfo(Motor* a) {
	a->Display();
}
void main()
{
	Car car1(5, 4, 1000, "TK", "TK_DS");
	Bus bus1(34, 6, 8000, "TK", "TK_DS",3);
	Truck truck1(2, 12, 11000, "TK", "TK_DS",8);
	Motor* pr = &car1;
	ShowInfo(pr);
	pr = &bus1;
	ShowInfo(pr);
	pr = &truck1;
	ShowInfo(pr);
}