怎么把程序代码补充完整

Question

#include<iostream>
using namespace std;
const double pi=3.14;
class Circle{    
public:    
double area(){return x*x*pi}    
Circle(double a):x(a){}    
private:double x;
};
class Rectangel{    
public:    
(                       )//写出矩形类的构造函数    
(                       )//写出计算矩形面积的函数    
private:
double len,wid;
};
class Square{    
public:    
(                       )//写出正方形类的构造函数    
(                       )//写出计算正方形面积的函数    
private:double len;
};
int main()   {    
cout<<" Input shape" <<endl;    
cout<<" If circle,input c,if rectangle input r;
if square input s" <<endl;    
char shape;;
cin>>shape;
switch(shape)
{case 'c':{double r;            
cout<<" input radius" <<endl;            
cin>>r;            
Circle r1(r);            
cout<<" circle area=" <<r1.area()<<endl;            
break;            
}
case  'r':{double len,wid;            
cout<<" input length and width" <<endl;            
cin>>len>>wid;            
(                       )//构造矩形对象，宽为：wid,高为len            
(                       )//输出矩形的面积            
break;            
}
case  's':{double len;            
cout<<" input length" <<endl;            
cin>>len;            
(                       )//构造正方形对象，边长为len            
(                       )//输出正方形的面积            
break;            
}    
 default:cout<<" input error! " <<endl;      
break;  
}    
return 0;
}

Answer 1

class Circle里有例子，参考下来就行了。

#include <iostream>
using namespace std;
const double pi = 3.14;
class Circle
{
public:
    double area() { return x * x * pi; }
    Circle(double a) : x(a) {}

private:
    double x;
};
class Rectangel
{
public:
    //(                       )//写出矩形类的构造函数
    Rectangel() { len = wid = 0; }
    Rectangel(double l, double w) : len(l), wid(w) {}
    //(                       )//写出计算矩形面积的函数
    double area() { return len * wid; }

private:
    double len, wid;
};
class Square
{
public:
    //(                       )//写出正方形类的构造函数
    Square(double l) : len(l) {}
    //(                       )//写出计算正方形面积的函数
    double area() { return len * len; }

private:
    double len;
};
int main()
{
    cout << " Input shape" << endl;
    cout << " If circle,input c,if rectangle input r; if square input s " << endl;
    char shape;
    cin >> shape;
    switch (shape)
    {
    case 'c':
    {
        double r;
        cout << " input radius" << endl;
        cin >> r;
        Circle r1(r);
        cout << " circle area=" << r1.area() << endl;
        break;
    }
    case 'r':
    {
        double len, wid;
        cout << " input length and width" << endl;
        cin >> len >> wid;
        //(                       )//构造矩形对象，宽为：wid,高为len
        Rectangel rect(len, wid);
        //(                       )//输出矩形的面积
        cout << rect.area() << endl;
        break;
    }
    case 's':
    {
        double len;
        cout << " input length" << endl;
        cin >> len;
        //(                       )//构造正方形对象，边长为len
        Square s(len);
        //(                       )//输出正方形的面积
        cout << s.area() << endl;
        break;
    }
    default:
        cout << " input error! " << endl;
        break;
    }
    return 0;
}