阅读以下说明和C++程序，将应填入(n)处的字句写在对应栏内。
【说明】
以下程序的功能是计算三角形、矩形和正方形的周长并输出。
程序由4个类组成：类Triangle、Rectangle和Square分别表示三角形、矩形和正方形；抽象类 Figure提供了一个纯虚拟函数getGirth()，作为计算上述3种图形周长的通用接口。
【C++程序】
# include ＜ iostream. h ＞
# include ＜ math. h ＞
class Figure {
public:
virtual double getGirth() =0; //纯虚拟函数 };
class Rectangle: (1) {
protected:
double height;
double width;
public:
Rectangle(){};
Rectangle( double height, double width) {
this→height = height;
this→width = width;
}
double getGirth ( ) {
return (2) ;
}
}；
class Square: (3) {
public:
Square( double width) {
(4) ;
} }；
class Triangle: (5) {
double la;
double lb;
double lc;
public:
Triangle( double la,double lb,double lc){
this→la = la; this→Lb = lb; this→lc = lc;
}
double getGirth ( ) {
}
return la + lb + lc;
}
};
void main( ) {
Figure * figures[ 3 ] = {
new Triangle ( 2,3,3 ),new Rectangle (5,8) , new Square (5) };
for (inti =0;i＜3;i++){
cout ＜ ＜ "figures [" ＜ ＜ i ＜ ＜" ] girth =" ＜ ＜ ( figures [ i ] ) →getGirth ( ) ＜ ＜ end1;
}
}
