计算不同形状的面积

#include<iostream.h>
#include<math.h>
#define pi 3.14
class cshape
{
	int x,y;
public:
	cshape(int x1,int y1)
	{
		x=x1;
		y=y1;
	}
	virtual float getarea(){return 0;};
};
class trial:public cshape
{
	int i,j,k;
public:
	trial(int i1,int j1,int k1,int x1,int y1):cshape(x1,y1)
	{
		i=i1;
		j=j1;
		k=k1;
	}
	float p;
	float getarea()
	{
       p=(float)(i+j+k)/2;
	   return (float)sqrt(p*(p-i)*(p-j)*(p-k));                              
	}
};
class squrt:public cshape
{
	int a;
public:
	squrt(int a1,int x1,int y1):cshape(x1,y1)
	{                                                                                     		a=a1;
	}
	float getarea()
	{
		return (float)a*a;
	}
};
class circle:public cshape
{
	int r;
public:
	circle(int r1,int x1,int y1):cshape(x1,y1)
	{
		r=r1;
	}
	float getarea()
	{
		return (float)pi*r*r;
	}
};
void getarea1(cshape &l)
{
   cout<<l.getarea()<<endl;
}
void main()
{
	int i1,j1,k1,a1,r1,m,x1=0,y1=0;
	cout<<"************(1)三角形****************"<<endl;
	cout<<"************(2)正方形****************"<<endl;
	cout<<"************(3)圆********************"<<endl;
	cout<<"请输入你要计算面积的图形的序号"<<endl;
	cin>>m;
	if(m==1)
	{
		cout<<"请输入三边的长度"<<endl;
	    cin>>i1>>j1>>k1;
		int n;
		n=(i1+j1+k1)/2;
		if(n*(n-i1)*(n-j1)*(n-k1)<=0)
			cout<<"无法组成三角形"<<endl;
		else
		{
			trial tri(i1,j1,k1,x1,y1);
		    getarea1(tri);
		}
	}
	else if(m==2)
	{
		cout<<"请输入正方形的边长"<<endl;
		cin>>a1;
		squrt squ(a1,x1,y1);
		getarea1(squ);
	}
	    else
		{
			cout<<"请输入圆的半径"<<endl;
			cin>>r1;
			circle cir(r1,x1,y1);
			getarea1(cir);
		}
}