YTU-OJ-Problem C: C++習題 抽象基類

kewlgrl發表於2015-07-21
C++抽象

Problem C: C++習題 抽象基類

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

Description

編寫一個程式，宣告抽象基類Shape，由它派生出3個派生類： Circle(圓形)、Rectangle(矩形)、Triangle(三角形)，用一個函式printArea分別輸出以上三者的面積（結果保留兩位小數），3個圖形的資料在定義物件時給定。

Input

圓的半徑
矩形的邊長
三角形的底與高

Output

圓的面積
矩形的面積
三角形的面積

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

 主函式已給定如下，提交時不需要包含，會自動新增到程式尾部


/* C++程式碼 */


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;
}


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