14.2-平面面积OJ版

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/**Copyright (c) 2013 ,烟台大学计算机学院*All rights reserved.*作者：张凤宁*完成日期：2014年6月4*版本号：v1.0*问题描述：*样例输入：*样例输出：*问题分析：用简单的方法，学会活学活用*/#include <iostream>#include <cmath>#include <iomanip>using namespace std;class Shape{public:    virtual float area()const    {        return 0.0;    };};//圆形class Circle:public Shape{public:    Circle(float r):radius(r) {};    virtual float area() const;private:    float radius;};float Circle::area() const{    return 3.14159*radius*radius;}//正方形class Square:public Shape{public:    Square(float m):a(m) {};    virtual float area()const;private:    float a;};float Square::area()const{    return a*a;}//矩形class Rectangle:public Shape{public:    Rectangle(float l,float w):a(l),b(w) {};    virtual float area() const;private:    float a;    float b;};float Rectangle::area()const{    return a*b;}//梯形class Trapezoid:public Shape{public:    Trapezoid(float a1,float a2,float h1):w1(a1),w2(a2),h(h1) {};    virtual float area()const;private:    float w1;    float w2;    float h;};float Trapezoid::area()const{    return ((w1+w2)*h)/2;}//三角形class Triangle:public Shape{public:    Triangle(float x,float n):w(x),h(n) {};    virtual float area()const;private:    float w;    float h;};float Triangle::area()const{    return (w*h)/2;}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}; //定义基类指针数组pt，使它每一个元素指向一个派生类对象    double areas=0.0; //areas为总面积    for(int i=0; i<5; i++)    {        areas=areas + pt[i]->area();    }    cout<<"totol of all areas="<<areas<<endl;   //输出总面积    return 0;}
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