C++习题 抽象基类

Problem G: C++习题 抽象基类

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 101  Solved: 81
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Description

编写一个程序，声明抽象基类Shape，由它派生出3个派生类： Circle(圆形)、Rectangle(矩形)、Triangle(三角形)，用一个函数printArea分别输出以上三者的面积（结果保留两位小数），3个图形的数据在定义对象时给定。

Input

圆的半径
矩形的边长
三角形的底与高

Output

圆的面积
矩形的面积
三角形的面积

Sample Input

12.64.5 8.44.5 8.4

Sample Output

area of circle = 498.76area of rectangle = 37.80area of triangle = 18.90

HINT

 主函数已给定如下，提交时不需要包含，会自动添加到程序尾部

/* C++代码 */

int main()

{

    float r,a,b,w,h;

    cout<<fixed<<setprecision(2);

    cin>>r;

    Circle circle(r);

    cout<<"area of circle = ";

    printArea(circle);

    cin>>a>>b;

    Rectangle rectangle(a,b);

    cout<<"area of rectangle = ";

    printArea(rectangle);

    cin>>w>>h;

    Triangle triangle(w,h);

    cout<<"area of triangle = ";

    printArea(triangle);

    return 0;

}

 

 

#include<iostream>#include<cstdio>using namespace std;class Shape{public:    virtual float printArea() const=0;};class Circle:public Shape{public:    Circle(float r):radius(r) {}    virtual float  printArea()const    {        return 3.141592*radius*radius;    }private:    float radius;};class Rectangle:public Shape{public:    Rectangle(float l,float w):length(l),width(w) {}    virtual float printArea()const    {        return length*width;    }private:    float length;    float width;};class Triangle:public Shape{public:    Triangle(float h,float w):hight(h),width(w) {}    virtual  float printArea()const    {        return 0.5*hight*width;    }private:    float hight;    float width;};void printArea(Circle&t){    cout<<t.printArea()<<endl;}void printArea(Rectangle&t){    cout<<t.printArea()<<endl;}void printArea(Triangle&t){    cout<<t.printArea()<<endl;}