C++实训（3.1）

多态的实现

源程序：

#include <iostream>
#include <cmath>
using namespace std;
class CShape
{
protected:
double acreage;
public:
CShape()
{
//cout<<"基类构造函数"<<endl;
};
virtual ~CShape()
{
//cout<<"基类析构函数"<<endl;
}
virtual double CalAcr()
{
return 0;
};
virtual void setAcreage(double acre) {};
virtual void PrintInfo() {};
};
class CRectangle :public CShape
{
double width, high;
public:
CRectangle(double w, double h)
{
//cout<<"矩形带参构造函数"<<endl;
width = w;
high = h;
};
CRectangle()
{
//cout<<"矩形无参构造函数"<<endl;
width = 0;
high = 0;
};
~CRectangle()
{
//cout<<"矩形析构函数"<<endl;
}
double CalAcr(); //前面加不加virtual，它都是虚函数，下面两个也同样
void PrintInfo();
void setAcreage(double);
};
class CCircle :public CShape
{
double radius;
public:
CCircle(double r)
{
//cout<<"圆形带参构造函数"<<endl;
radius = r;
};
CCircle()
{
//cout<<"圆形无参构造函数"<<endl;
radius = 0;
};
~CCircle()
{
//cout<<"圆形析构函数"<<endl;
}
virtual double CalAcr();
virtual void PrintInfo();
virtual void setAcreage(double);
};
class CTriangle :public CShape
{
double a, b, c;
public:
CTriangle(double a, double b, double c)
{
//cout<<"三角形带参构造函数"<<endl;
this->a = a;
this->b = b;
this->c = c;
};
CTriangle()
{
//cout<<"三角形无参构造函数"<<endl;
a = 0;
b = 0;
c = 0;
};
~CTriangle()
{
//cout<<"三角形析构函数"<<endl;
};
virtual double CalAcr();
virtual void PrintInfo();
virtual void setAcreage(double);
};
double CRectangle::CalAcr()
{
return width * high;
}
void CRectangle::PrintInfo()
{
cout << "矩形. 宽度=" << this->width << ",高度 =" << this->high << ", 面积" << this->acreage << endl;
}
void CRectangle::setAcreage(double acre)
{
acreage = acre;
}
double CCircle::CalAcr()
{
return 3.14 * radius * radius;
}
void CCircle::PrintInfo()
{
cout << "圆. 半径=" << this->radius << ",面积" << this->acreage << endl;
}
void CCircle::setAcreage(double acre)
{
acreage = acre;
}
double CTriangle::CalAcr()
{
double p = (a + b + c) / 2.0;
return sqrt(p * (p - a) * (p - b) * (p - c));
}
void CTriangle::PrintInfo()
{
cout << "三角形.三条边分别是: " << this->a << "," << this->b << "," << this->c << ",面积=" << this->acreage << endl;
}
void CTriangle::setAcreage(double acre)
{
acreage = acre;
}
CShape* pShapes[100];
int main()
{
int i, n;
double temp1, temp2, temp3;
CRectangle* pr; CCircle* pc; CTriangle* pt;
cin >> n;
for (i = 0; i < n; ++i)
{
char c;
cin >> c;
switch (c)
{
case'R':case'r':
cin >> temp1 >> temp2;
pr = new CRectangle(temp1, temp2);
pr->setAcreage(pr->CalAcr());
pShapes[i] = pr;
break;
case'C':case'c':
cin >> temp1;
pc = new CCircle(temp1);
pc->setAcreage(pc->CalAcr());
pShapes[i] = pc;
break;
case'T':case't':
cin >> temp1 >> temp2 >> temp3;
pt = new CTriangle(temp1, temp2, temp3);
pt->setAcreage(pt->CalAcr());
pShapes[i] = pt;
break;
}
}
if (n == 1)
cout << "共有 " << n << "种图形，它是" << endl;
else
cout << "共有 " << n << "种图形，分别是" << endl;
for (i = 0; i < n; ++i)
{
//cout<<"1"<<endl;
pShapes[i]->PrintInfo();
delete pShapes[i];
}
system("pause");
return 0;
}

//c++删除空白行    用空格替换 ^s*  

运行结果：