HDU 1086 计算几何 求线段交点（吉大模板）

模板直接解决。。

#include
#include 
#include 
using namespace std;
const double eps=1e-10;

struct point { double x, y; };
double min(double a, double b) { return a < b ? a : b; }
double max(double a, double b) { return a > b ? a : b; }
bool inter(point a, point b, point c, point d){
	if ( min(a.x, b.x) > max(c.x, d.x) ||
		min(a.y, b.y) > max(c.y, d.y) ||
		min(c.x, d.x) > max(a.x, b.x) ||
		min(c.y, d.y) > max(a.y, b.y) ) return 0;
	double h, i, j, k;
	h = (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
	i = (b.x - a.x) * (d.y - a.y) - (b.y - a.y) * (d.x - a.x);
	j = (d.x - c.x) * (a.y - c.y) - (d.y - c.y) * (a.x - c.x);
	k = (d.x - c.x) * (b.y - c.y) - (d.y - c.y) * (b.x - c.x);
	return h * i <= eps && j * k <= eps;
}

int main()
{
	int n;
	point p[105][2];
	while(cin >> n, n)
	{
		for(int i = 0; i < n; i++)
			scanf("%lf%lf%lf%lf", &p[i][0].x, &p[i][0].y, &p[i][1].x, &p[i][1].y);

		int sum = 0;
		for(int i = 0; i < n; i++)
		{
			for(int j = i+1; j < n; j++)
			{
				if(inter(p[i][0], p[i][1], p[j][0], p[j][1]))
					sum += 1;
			}
		}
		cout << sum << endl;
	}
}