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一、你是個物件導向程式設計師，你首先寫了兩個 C++ 的類別，其程式碼如下：

Class Rectangle {

private:

float width;

float height;

public:

Rectangle(float width, float height) : width(width), height(height) { }

float getArea( ) const { return width * height; }

};

Class Circle {

private:

float radius;

public:

Circle(float radius): radius(radius) { }

float getArea( ) const { return 3.14159f * radius * radius; }

};

然後你繼續寫一個 main( ) 來完成你的實作。你的同事會幫你完成一個generateData( ) 的副程式，它會負責產生一堆 Rectangle 或 Circle 裝在一個 vector container，然後回傳。你的目標是將 vector container 裡面的每一個物件的面積通通加總。

int main( ) {

...

... = generateData( );

...

}

你想要用多形 (polymorphism) 來完成這件事情。請撰寫未完成的 main( )以及你需要對 Rectangle, Circle 兩個 class 的原始程式碼做任何的修改。（25分）

#include <iostream>

#include <vector>

using namespace std;

class Shape {

public:

virtual float getArea( ) const {return 0;};

};

class Rectangle:virtual public Shape {

private:

float width;

float height;

public:

Rectangle(float width, float height) : width(width), height(height) { }

float getArea( ) const { return width * height; }

};

class Circle:virtual public Shape {

private:

float radius;

public:

Circle(float radius): radius(radius) { }

float getArea( ) const { return 3.14159f * radius * radius; }

};

vector <Shape *> generateData( ) {

vector<Shape *> v1;

v1.push_back(new Rectangle(5.5f, 8.7f));

v1.push_back(new Circle(2));

v1.push_back(new Circle(8));

v1.push_back(new Rectangle(3.0f, 5.1f));

return v1;

}

int main(void) {

vector<Shape *> v1;

v1 = generateData( );

vector <Shape *>::iterator Iter;

float sum = 0;

for(Iter = v1.begin( ); Iter != v1.end( ) ; Iter++) {

// cout << (*Iter)->getArea() << endl;

sum = sum+(*Iter)->getArea( );

}

cout << "加總面積 = " << sum << endl;

return 0;

}