YTU-OJ-Problem C: C++习题 抽象基类

Problem C: C++习题 抽象基类

Time Limit: 1 Sec   Memory Limit: 128 MB
Submit: 717   Solved: 529
[ Submit][ Status][ Web Board]

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

12.6
4.5 8.4
4.5 8.4

Sample Output

area of circle = 498.76
area of rectangle = 37.80
area 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>
#include<iomanip>
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;
}
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;
}