C++习题 虚函数-计算图形面积

C++习题 虚函数-计算图形面积

时间: 1ms        内存:128M

描述:

编写一个程序,定义抽象基类Shape,由它派生出5个派生类: Circle(圆形)、Square(正方形)、Rectangle(矩形)、Trapezoid(梯形)、Triangle(三角形)。
用虚函数分别计算几种图形面积,并求它们之和。
要求用基类指针数组,使它每一个元素指向一个派生类对象。 

输入:

圆的半径
正方形的边长
矩形的边长
梯形的上底和下底,高
三角形的底与高

输出:

所有图形面积之和(结果保留两位小数)

示例输入:

12.6
3.5
4.5 8.4
2.0 4.5 3.2
4.5 8.4

示例输出:

total of all areas=574.11

提示:

参考答案(内存最优[1268]):

#include <iostream>
#include <iomanip>
using namespace std;
//定义抽象基类Shape
class Shape
{
public:
    virtual double area() const =0;     //纯虚函数
};

//定义Circle(圆形)类
class Circle:public Shape
{
public:
    Circle(double r):radius(r) {}      //结构函数
    virtual double area() const
    {
        return 3.14159*radius*radius;
    };   //定义虚函数
protected:
    double radius;                    //半径
};

//定义Square(正方形)类
class Square:public Shape
{
public:
    Square(double s):side(s) {}         //结构函数
    virtual double area() const
    {
        return side*side;   //定义虚函数
    }
protected:
    double side;
};

//定义Rectangle(矩形)类
class Rectangle:public Shape
{
public:
    Rectangle(double w,double h):width(w),height(h) {}    //结构函数
    virtual double area() const
    {
        return width*height;   //定义虚函数
    }
protected:
    double width,height;    //宽与高
};

//定义Trapezoid(梯形)类
class Trapezoid:public Shape
{
public:
    Trapezoid(double t,double b,double h):top(t),bottom(t),height(h) {} //结构函数
    virtual double area() const
    {
        return 0.5*(top+bottom)*height;   //定义虚函数
    }
protected:
    double top,bottom,height;        //上底、下底与高
};

//定义Triangle(三角形)类
class Triangle:public Shape
{
public:
    Triangle(double w,double h):width(w),height(h) {}               //结构函数
    virtual double area() const
    {
        return 0.5*width*height;   //定义虚函数
    }
protected:
    double width,height;                                            //宽与高
};

int main()
{
    float r,a,b,w1,w2,w,h;
    cout<<fixed<<setprecision(2);
    cin>>r;
    Circle circle(r);
    cin>>a;
    Square square(a);
    cin>>a>>b;
    Rectangle rectangle(a,b);
    cin>>w1>>w2>>h;
    Trapezoid trapezoid(w1,w1,h);
    cin>>w>>h;
    Triangle triangle(w,h);
    Shape *pt[5]= {&circle,&square,&rectangle,&trapezoid,&triangle};
    double areas=0.0;
    for(int i=0; i<5; i++)
        areas=areas+pt[i]->area();
    cout<<"total of all areas="<<areas<<endl;
    return 0;
}

参考答案(时间最优[0]):

#include <iostream>
#include <iomanip>
using namespace std;
//定义抽象基类Shape
class Shape
{
public:
    virtual double area() const =0;     //纯虚函数
};

//定义Circle(圆形)类
class Circle:public Shape
{
public:
    Circle(double r):radius(r) {}      //结构函数
    virtual double area() const
    {
        return 3.14159*radius*radius;
    };   //定义虚函数
protected:
    double radius;                    //半径
};

//定义Square(正方形)类
class Square:public Shape
{
public:
    Square(double s):side(s) {}         //结构函数
    virtual double area() const
    {
        return side*side;   //定义虚函数
    }
protected:
    double side;
};

//定义Rectangle(矩形)类
class Rectangle:public Shape
{
public:
    Rectangle(double w,double h):width(w),height(h) {}    //结构函数
    virtual double area() const
    {
        return width*height;   //定义虚函数
    }
protected:
    double width,height;    //宽与高
};

//定义Trapezoid(梯形)类
class Trapezoid:public Shape
{
public:
    Trapezoid(double t,double b,double h):top(t),bottom(t),height(h) {} //结构函数
    virtual double area() const
    {
        return 0.5*(top+bottom)*height;   //定义虚函数
    }
protected:
    double top,bottom,height;        //上底、下底与高
};

//定义Triangle(三角形)类
class Triangle:public Shape
{
public:
    Triangle(double w,double h):width(w),height(h) {}               //结构函数
    virtual double area() const
    {
        return 0.5*width*height;   //定义虚函数
    }
protected:
    double width,height;                                            //宽与高
};

int main()
{
    float r,a,b,w1,w2,w,h;
    cout<<fixed<<setprecision(2);
    cin>>r;
    Circle circle(r);
    cin>>a;
    Square square(a);
    cin>>a>>b;
    Rectangle rectangle(a,b);
    cin>>w1>>w2>>h;
    Trapezoid trapezoid(w1,w1,h);
    cin>>w>>h;
    Triangle triangle(w,h);
    Shape *pt[5]= {&circle,&square,&rectangle,&trapezoid,&triangle};
    double areas=0.0;
    for(int i=0; i<5; i++)
        areas=areas+pt[i]->area();
    cout<<"total of all areas="<<areas<<endl;
    return 0;
}

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