内容提要
对于类MyString,要求重载‘+’运算符后可以计算表达式:a=b+c;表示两个字符串连接。其中a,b,c都是类MyString的对象。使用虚函数编写程序求球体和圆柱体的体积及表面积。由于球体和圆柱体都可以看作由圆继承而来，所以可以定义圆类Circle作为基类。在Circle类中定义一个数据成员radius和两个虚函数area()和volume()。由Circle类派生Sphere类和Column类。在派生类中对虚函数area()和volume()重新定义，分别求球体和圆柱体的体积及表面积。基本要求重载相应的运算符并编写程序，能运用虚函数编写程序测试并提交程序。
运算符重载:
#pragma warning(disable:4996)
#include <iostream>
#include <cstring>
#define N 32
using namespace std;
class MyString
{
char *data;
int len;
public:
MyString() { data = new char[N]; len = 0; }
MyString(const char* a);
MyString& operator + (MyString & a);
MyString& operator + (char * a);
MyString& operator + (const char *a);
MyString& operator = (MyString & a);
MyString& operator = (char * a);
MyString& operator = (const char *a);
int strLen(void) { return len; }
char * Data(void) { return data; }
friend ostream & operator << (ostream &os, MyString &a);
//friend istream & operator >> (istream &is, MyString &a);
};
MyString::MyString(const char *a)
{
data = new char[strlen(a) + 1];
strcpy(data, a);
len = strlen(a);
}
MyString& MyString::operator + (MyString & a)
{
if (len + a.strLen() > (N - 1))
{
//分配一段新的控件并将两个字符串拼接起来
char *tmp = new char[len + a.strLen() + 1];
strcpy(tmp, data);
strcat(tmp, a.Data());
data = tmp;
}
else
{
strcat(data, a.Data());
}
len += a.strLen();
return *this;
}
MyString& MyString::operator + (char * a)
{
if (len + strlen(a) > (N - 1))
{
char *tmp = new char[len + strlen(a) + 1];
strcpy(tmp, data);
strcat(tmp, a);
data = tmp;
}
else
{
strcat(data, a);
}
len += strlen(a);
return *this;
}
MyString& MyString::operator + (const char *a)
{
if (len + strlen(a) > (N - 1))
{
char *tmp = new char[len + strlen(a) + 1];
strcpy(tmp, data);
strcat(tmp, a);
data = tmp;
}
else
{
strcat(data, a);
}
len += strlen(a);
return *this;
}
MyString& MyString::operator = (MyString & a)
{
if (&a != this && len > 0 && len < a.strLen())
{
delete[] data;
data = new char[a.strLen() + 1];
}
strcpy(data, a.Data());
len = a.strLen();
return *this;
}
MyString& MyString::operator = (char * a)
{
if (data != nullptr && len < strlen(a))
{
delete[] data;
data = new char[strlen(a) + 1];
}
strcpy(data, a);
len = strlen(a);
return *this;
}
MyString& MyString::operator = (const char *a)
{
if (data != nullptr && len < strlen(a))
{
delete[] data;
data = new char[strlen(a) + 1];
}
strcpy(data, a);
len = strlen(a);
return *this;
}
ostream & operator << (ostream &os, MyString &a)
{
os << a.Data();
return os;
}
int main(void)
{
MyString str("清风朗月 ");
str = str + "辙思玄度";
cout << str << endl;
str = str + ".我与春风皆过客,谁共明月赴长生.";
cout << str << endl;
str = "你只见草木皆兵,我却看浩瀚苍穹";
cout << str << endl;
char tmp[] = "星河滚烫,你是人间理想;";
str = tmp;
cout << str << endl;
system("pause");
return 0;
}
虚函数的代码:
#include <iostream>
#define PIE 3.1415
using namespace std;
//圆，接口类
class Circle
{
protected:
double radius;
public:
//表面积
virtual double area(void) = 0;
//体积
virtual double volume(void) = 0;
};
//球
class Sphere :public Circle
{
public:
Sphere(double r = 0) { radius = r; }
//表面积
virtual double area(void)
{
return 4.0 * PIE * radius * radius;
}
//体积
virtual double volume(void)
{
return (4.0 / 3.0) * PIE * radius * radius * radius;
}
};
//圆柱
class Column :public Circle
{
private:
double height;
public:
Column(double r = 0, double h = 0) { radius = r; height = h; }
//表面积
virtual double area(void)
{
if (0 == height)
{
//底面积
return PIE * radius * radius;
}
return 2.0* PIE * radius * radius + PIE * 2.0 * radius * height;
}
//体积
virtual double volume(void)
{
if (0 == height)
{
return 0;
}
return PIE * radius * radius * height;
}
};
int main(void)
{
double rS, rC, h;
while (true)
{
cout << "请输入球体的半径：";
cin >> rS;
if (rS <= 0)
{
cout << "请输入大于0的数据！\n\n";
}
else
break;
}
while (true)
{
cout << "请输入圆柱体的半径：";
cin >> rC;
if (rC <= 0)
{
cout << "请输入大于0的数据！\n\n";
}
else
break;
}
while (true)
{
cout << "请输入圆柱体的高：";
cin >> h;
if (h <= 0)
{
cout << "请输入大于0的数据！\n\n";
}
else
break;
}
Sphere sphere(rS);
Column column(rC, h);
cout << "球体的半径为：" << rS << endl
<< "球体的表面积为：" << sphere.area() << endl
<< "球体的体积为：" << sphere.volume() << endl << endl;
cout << "圆柱体的半径为：" << rC << endl
<< "圆柱体的表面积为：" << column.area() << endl
<< "圆柱体的体积为：" << column.volume() << endl << endl;
system("pause");
return 0;
}
