hdu1086

#include <iostream> #include <stdio.h> #include <string.h> #include <stack> #include <queue> #include <map> #include <set> #include <vector> #include <math.h> #include <algorithm> using namespace std; const double pi = acos(-1.0); const int INF = 0x3f3f3f3f;

struct Line { double x1,y1,x2,y2; }node[105];

bool solve(Line a, Line b)//叉积判断两线段是否相交 { if (((a.x1-b.x1)*(a.y2-b.y1)-(a.x2-b.x1)*(a.y1-b.y1))*((a.x1-b.x2)*(a.y2-b.y2)-(a.x2-b.x2)*(a.y1-b.y2))>0) return false; if (((b.x1-a.x1)*(b.y2-a.y1)-(b.x2-a.x1)*(b.y1-a.y1))*((b.x1-a.x2)*(b.y2-a.y2)-(b.x2-a.x2)*(b.y1-a.y2))>0) return false; return true; }

int main () { int n; while (scanf ("%d",&n),n) { for (int i=0; i<n; i++) scanf ("%lf%lf%lf%lf",&node[i].x1,&node[i].y1,&node[i].x2,&node[i].y2); int cnt = 0; for (int i=0; i<n; i++) { for (int j=i+1; j<n; j++) { if (solve(node[i], node[j])) cnt++; } } printf ("%d\n",cnt); } return 0; }