POJ 1269

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#include<string.h>
#include<algorithm>
#define eps 1e-8
using namespace std;

struct node
{
    int x1,y1;
    int x2,y2;
}L[10];
double x,y;

int max(int a,int b) {if(a>b) return a;return b;}
int min(int a,int b) {if(a<b) return a;return b; }

double multiply1(node a,node b) 
{
    return (a.x1-a.x2)*(b.y1-a.y1)-(a.y1-a.y2)*(b.x1-a.x1);
}
double multiply2(node a,node b)
{
    return (a.x1-a.x2)*(b.y2-a.y1)-(a.y1-a.y2)*(b.x2-a.x1);
}
bool inter(node a,node b)
{
      if(max(a.x1,a.x2)>=min(b.x1,b.x2)&&
      max(b.x1,b.x2)>=min(a.x1,a.x2)&&
      max(a.y1,a.y2)>=min(b.y1,b.y2)&&
      max(b.y1,b.y2)>=min(a.y1,a.y2)&&
      multiply1(a,b)*multiply2(a,b)<=0&&//判断线段b的两个端点是否在线段a的两侧
      multiply1(b,a)*multiply2(b,a)<=0)//判断线段a的两个端点是否在线段b的两侧 
      return true;
      else return false;
}

void  GetInter(node a,node b)
{
	int A1=a.y1-a.y2;
	int B1=a.x2-a.x1;
	int C1=A1*a.x1+B1*a.y1;
	int A2=b.y1-b.y2;
	int B2=b.x2-b.x1;
	int C2=A2*b.x1+B2*b.y1;
	y=(A2*C1-A1*C2)*1.0/(A2*B1-A1*B2);
	x=(B2*C1-B1*C2)*1.0/(A1*B2-A2*B1);
}

bool Judge(node a,node b)
{
	double p1=a.x1-a.x2;
	double q1=a.y1-a.y2;
	double p2=b.x1-b.x2;
	double q2=b.y1-b.y2;
	if(fabs(p1-0)<=eps && fabs(p2-0)<=eps)
		return true;
	if(fabs(p1-0)<=eps && fabs(p2-0)>=eps || fabs(p1-0)>=eps && fabs(p2-0)<=eps)
		return false;
	double k1=q1*1.0/p1;
	double k2=q2*1.0/p2;
	if(fabs(k1-k2)<=eps)
		return true;
	return false;
}

int main()
{
	int n;
	int i;
	scanf("%d",&n);
	printf("INTERSECTING LINES OUTPUT\n");
	while(n--)
	{
		for(i=0;i<2;i++)
			scanf("%d%d%d%d",&L[i].x1,&L[i].y1,&L[i].x2,&L[i].y2);
		
		if(inter(L[0],L[1]) )
		{
			if(Judge(L[0],L[1]))
				printf("LINE\n");
			else
			{
				GetInter(L[0],L[1]);
				printf("POINT %.2lf %.2lf\n",x,y);
			}
		}
		else if(Judge(L[0],L[1]))
		{
			if(fabs(multiply1(L[0],L[1])-0)<eps)
				printf("LINE\n");
			else printf("NONE\n");
		}
		else
		{
			GetInter(L[0],L[1]);
				printf("POINT %.2lf %.2lf\n",x,y);
		}
	}
	printf("END OF OUTPUT\n");
	return 0;
}