~!.cpp

三角形面积的经典算法！ 里面有多种方法求解！

#include<iostream.h>
#include<math.h>
class CPoint
{
public:
	float x, y;
	void input()
	{
		cout<<"请输入坐标的横坐标：";
	    cin>>x;
		cout<<"请输入坐标的纵坐标：";
	    cin>>y;
	    cout<<endl;
	}
};

class tria
{
private:
	CPoint A, B, C;
	double a[4];
public:
    void set();
	void area();
};
void tria::set()
{
	
	A.input();
	B.input();
	C.input();
	cout<<"("<<A.x<<","<<A.y<<")"<<endl
		<<"("<<B.x<<","<<B.y<<")"<<endl
		<<"("<<C.x<<","<<C.y<<")"<<endl;
	if((A.x==B.x)&&(A.y==B.y)||(A.x==C.x)&&(A.y==C.y)||(C.x==B.x)&&(C.y==B.y))
	{cout<<"有重点!!!无法构成三角形!!!!!"<<endl;}
	else if((A.x/B.x==A.y/B.y)&&(A.x/C.x==A.y/C.y)&&(B.x/C.x==B.y/C.y))
	{cout<<"三个点在一条直线上!!!!!!!无法构成三角形!!!!!"<<endl;}
	else
	{
	 a[1]=sqrt((A.x-B.x)*(A.x-B.x)+(A.y-B.y)*(A.y-B.y));
	 a[2]=sqrt((B.x-C.x)*(B.x-C.x)+(B.y-C.y)*(B.y-C.y));
	 a[3]=sqrt((C.x-A.x)*(C.x-A.x)+(C.y-A.y)*(C.y-A.y)); 
	}
}
void tria::area()
{
	double s;
	s=(a[1]+a[2]+a[3])/2;
	cout<<"三角形面积:"<<sqrt(s*(s-a[1])*(s-a[2])*(s-a[3]))<<endl;
}

void main()
{
	tria s;
	s.set();
	s.area();
}