Question

Description

There are 4 classes, Figure is the base class，both Triangle, Rectangle and Circle are all inherited from it. Figure class is like following:

class FIGURE {
public:
    void set_size(double x, double y = 0);
    virtual double get_area() = 0;  
protected:
    double x_size, y_size;
};

You should implement Figure, Triangle, Rectange, Circle class.

Output

Area of triangle is 60
Area of rectangle is 120
Area of circle is 706.858

//Figure.h

#ifndef FIGURE_H
#define FIGURE_H
const double PI = 3.14159;

class FIGURE
{
public:
void set_size(double x, double y = 0);
virtual double get_area() = 0;
protected:
double x_size, y_size;
};

#endif

//main.cpp

#include "Figure.h"
#include "Triangle.h"
#include "Rectangel.h"
#include "Circle.h"
#include <iostream>
using namespace std;

int main()
{
TRIANGLE triangle;     
RECTANGLE rectangle;      
CIRCLE circle;          

// 处理三角形
triangle.set_size(15, 8);   // 设置三角形的底和高
cout << "Area of triangle is " << triangle.get_area() << "\n";
  
// 处理矩形
rectangle.set_size(15, 8);   // 设置矩形的长和宽
cout << "Area of rectangle is " << rectangle.get_area() << "\n";
  
// 处理圆
circle.set_size(15);       // 设置圆的半径
cout << "Area of circle is " << circle.get_area() << "\n";
  
return 0;
}

Need to write: Figure.cpp, Triangle.h, Rectangle.h, Circle.h files

Above code can't be changed

Answer 1

Figure.cpp

#include<iostream>
using namespace std;

// parent class figure
class FIGURE {
public:
void set_size(double x, double y = 0);
virtual double get_area() = 0;
protected:
double x_size, y_size; // data members
};

// child class inherited from class Figure
class TRIANGLE:public FIGURE
{
   public:
   void set_size(double x, double y = 0)
   {
       x_size=x;
       y_size=y;
   }
   double get_area()
   {
       return x_size*y_size/2;
   }
};

// child class inherited from class Figure
class RECTANGLE:public FIGURE
{
   public:
   void set_size(double x, double y = 0)
   {
       x_size=x;
       y_size=y;
   }
   double get_area()
   {
       return x_size*y_size;
   }
};

// child class inherited from class Figure
class CIRCLE:public FIGURE
{
   public:
   void set_size(double x, double y = 0)
   {
       x_size=x;
   }
   double get_area()
   {
       return 3.14*x_size*x_size;
   }
};

int main()
{
   // creating object of TRIANGLE class
   TRIANGLE triangle;
   // creating object of RECTANGLE class
   RECTANGLE rectangle;   
   // creating object of CIRCLE class   
   CIRCLE circle;   
     
   triangle.set_size(15, 8); // 60
   cout << "Area of triangle is " << triangle.get_area() << "\n";
   rectangle.set_size(15, 8); // 120
   cout << "Area of rectangle is " << rectangle.get_area() << "\n";
   circle.set_size(15); // 706.5
   cout << "Area of circle is " << circle.get_area() << "\n";
  
   return 0;
}

Output