poj 1269 Intersecting Lines

#include <cstdio>
#include <cstring>

struct Point
{
int x,y;
};

struct Line
{
Point s,e;
};
Line line1,line2;

int det(int x1, int y1, int x2, int y2)
{
return x1*y2 - x2*y1;
}
/****求ab和ac叉积****/
int cross(Point a, Point b, Point c)
{
return det(b.x-a.x,b.y-a.y,c.x-a.x,c.y-a.y);
}

int area(Point a, Point b, Point c)
{
return cross(a,b,c);
}

int main()
{
int n;
while(scanf("%d",&n) != EOF)
{
printf("INTERSECTING LINES OUTPUT\n");
for(int i = 0; i < n; ++i)
{
scanf("%d %d %d %d %d %d %d %d",&line1.s.x,&line1.s.y,&line1.e.x,&line1.e.y,&line2.s.x,&line2.s.y,&line2.e.x,&line2.e.y);
//            line1.e.x-line1.s.x,line1.e.y-line1.s.y------>x1,y1
//            line2.e.x-line2.s.x,line2.e.y-line2.s.y------>x2,y2
if((line1.e.x-line1.s.x)*(line2.e.y-line2.s.y) - (line1.e.y-line1.s.y)*(line2.e.x-line2.s.x) == 0)//共线，然后判断平行还是重合
{
if(cross(line1.s,line1.e,line2.s) == 0)
printf("LINE\n");
else
printf("NONE\n");
}
//肯定就有交点了
else
{
float s1 = area(line1.s,line1.e,line2.s)/2.0;
float s2 = area(line1.s,line1.e,line2.e)/2.0;
printf("POINT %.2f %.2f\n",(s1*line2.e.x-s2*line2.s.x)/(s1-s2),(s1*line2.e.y-s2*line2.s.y)/(s1-s2));
}

}
printf("END OF OUTPUT\n");
}
return 0;
}