C++习题 虚函数-计算图形面积
Time Limit: 1 Sec Memory Limit: 128 MBSubmit: 122 Solved: 86
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Description
编写一个程序，定义抽象基类Shape，由它派生出5个派生类： Circle(圆形)、Square(正方形)、Rectangle(矩形)、Trapezoid(梯形)、Triangle(三角形)。
用虚函数分别计算几种图形面积，并求它们之和。
要求用基类指针数组，使它每个元素指向一个派生类对象。
Input
圆的半径
正方形的边长
矩形的边长
梯形的上底和下底，高
三角形的底与高
Output
全部图形面积之和（结果保留两位小数）
Sample Input
12.63.54.5 8.42.0 4.5 3.24.5 8.4
Sample Output
total of all areas=574.11
#include <iostream>
#include<iomanip>
using namespace std;
class Shape
{public:virtual float area()=0;private:};
class Circle:public Shape
{
public:Circle(float s){r=s;}
float area(){return (3.1415926*r*r);}private:float r;};class Square:public Shape
{
public:Square (float s){a=s;}float area() { return (a*a); }
private:float a;
};
class Rectangle :public Shape
{
public:Rectangle (float s,float d){a=s;b=d;}float area() { return (a*b);}
private:float a,b;
};
class Trapezoid:public Shape
{
public:Trapezoid (float s,float d,float ss){w1=s;w2=d;h=ss;}float area() { return ((w1+w2)*h/2); }
private:float w1,w2,h;
};
class Triangle:public Shape
{
public:Triangle (float s,float d){w=s;h=d;}float area() { return (w*h/2); }
private:float w,h;
};int main(){float r,a,b,w1,w2,w,h;cout<<fixed<<setprecision(2);cin>>r;Circle circle(r);cin>>a;Square square(a);cin>>a>>b;Rectangle rectangle(a,b);cin>>w1>>w2>>h;Trapezoid trapezoid(w1,w1,h);cin>>w>>h;Triangle triangle(w,h);Shape *pt[5]= {&circle,&square,&rectangle,&trapezoid,&triangle};double areas=0.0;for(int i=0; i<5; i++)areas=areas+pt[i]->area();cout<<"total of all areas="<<areas<<endl;return 0;}
)
)
