#include
#include
#include
#include
#define?NULL?0
#define?LEN?sizeof（struct?point）

struct?point
{
	char?ptname[8];
	float?x;	
	float?y;
	struct?point?*next;
};

struct?point*?creat（void）
{
	struct?point?*head;
	struct?point?*p1*p2;
	int?n=0;
	p1=p2=（struct?point*）malloc（LEN）;
	scanf（“%s“p1->ptname）;
	head=NULL;
	while（strcmp（p1->ptname“finish“）!=0）
	{
		printf（“請(qǐng)輸入該點(diǎn)X?Y坐標(biāo)\n“）;
		scanf（“%f%f“&p1->x&p1->y）;
		n=n+1;
		if（n==1）?
			head=p1;
		else
			p2->next=p1;
		p2=p1;
		p1=（struct?point*）malloc（LEN）;
		printf（“請(qǐng)輸入下一點(diǎn)點(diǎn)名\n“）;
		scanf（“%s“p1->ptname）;
	}
	p2->next=NULL;
	return（head）;
}

struct?point?*getlast（struct?point?*p）
{
	while（p->next!=NULL）
		p=p->next;
	return?p;
}

float?len（float?x1float?y1float?x2float?y2float?x3float?y3）
{
	float?abcsh;
	a=sqrt（（x3-x2）*（x3-x2）+（y3-y2）*（y3-y2））;
	b=sqrt（（x1-x2）*（x1-x2）+（y1-y2）*（y1-y2））;
	c=sqrt（（x3-x1）*（x3-x1）+（y3-y1）*（y3-y1））;
	s=0.5*（a+b+c）;
	h=（sqrt（s*（s-a）*（s-b）*（s-c）））*2/c;
	return?h;
}

void?doglas（struct?point?*headstruct?point?*lastfloat?si