多态应用实例一：几何形体程序

本文主要是介绍多态应用实例一：几何形体程序，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

用基类指针数组存放派生类对象的指针地址，是多态的常用应用，遍历该指针数组就能对各个派生类对象做各种操作。

problem

输入不同几何形体及其参数，要求按照面积大小顺序输出其对应的面积，以及集合形体形状。

code

#include <iostream>
#include <math.h>
#include<stdlib.h>
using namespace std;class CShape{public:virtual double Area() = 0;//纯虚函数virtual void PrintInfo() = 0;
};class CRectangle: public CShape{public:double l,w;double Area(){return l*w;}void PrintInfo(){cout<<"Rectangle: "<<Area()<<endl;}
};class CTriangle: public CShape{public:double a,b,c;double Area(){double p = (a+b+c)/2.0;return sqrt(p*(p-a)*(p-b)*(p-c));}void PrintInfo(){cout<<"Triangle: "<<Area()<<endl;}
};class CCircle: public CShape{public:double r;double Area(){return 3.14159*r*r;}void PrintInfo(){cout<<"Circle: "<<Area()<<endl;}
};
int comp(const void *s1,const void *s2){CShape **p1;CShape **p2;p1 = (CShape **)s1;p2 = (CShape **)s2;double d1,d2;d1 =  (*p1)->Area();d2 =  (*p2)->Area();return d1>d2?1:-1; 
}
int main(){CShape *pShapes[100];int n;cin>>n;char c;CRectangle *pr; CTriangle *pt; CCircle *pc;for(int i=0;i<n;i++){cin>>c;switch(c){case'R':pr = new CRectangle();cin>>pr->l>>pr->w;pShapes[i] = pr;break;case'T':pt = new CTriangle();cin>>pt->a>>pt->b>>pt->c;pShapes[i] = pt;break;case'C':pc = new CCircle();cin>>pc->r;pShapes[i] = pc;break;default: break;}}qsort(pShapes,n,sizeof(CShape *),comp);for(int i=0;i<n;i++){pShapes[i]->PrintInfo();}return 0;
}