POJ - 2653 - Pick-up sticks 线段与线段相交

判断线段与线段相交

莫名其妙的数据量

 #include <iostream>
 #include <cstdio>
 #include <vector>
 #include <cmath>
 #include <cstring>
 using namespace std;
 const double eps = 1e-;
 int dcmp(double x)
 {
     return fabs(x) < eps ?  : (x <  ? - : );
 }
 struct Point
 {
     double x,y;
     Point(double a = , double b = ) : x(a), y(b) {}
 };
 Point operator - (Point a, Point b)
 {
     return Point(a.x-b.x, a.y-b.y);
 }
 double Det(Point a, Point b)
 {
     return a.x * b.y - a.y * b.x;
 }
 double Dot(Point a, Point b)
 {
     return a.x*b.x + a.y*b.y;
 }
 bool OnSegment(Point p, Point a1, Point a2)
 {
     return dcmp(Det(a1 - p, a2 - p)) ==  && dcmp(Dot(a1 - p, a2 - p)) <= ;
 }
 bool SegCross(Point a1, Point a2, Point b1, Point b2)
 {
     double c1 = Det(a2 - a1, b1 - a1);
     double c2 = Det(a2 - a1, b2 - a1);
     double c3 = Det(b2 - b1, a1 - b1);
     double c4 = Det(b2 - b1, a2 - b1);
     if (dcmp(c1) * dcmp(c2) <  && dcmp(c3) * dcmp(c4) < ) return ;
     else if (OnSegment(b1, a1, a2) ) return ;
     else if (OnSegment(b2, a1, a2) ) return ;
     else if (OnSegment(a1, b1, b2) ) return ;
     else if (OnSegment(a2, b1, b2) ) return ;
     else return ;
 }

 struct Line
 {
     Point s,e;
     Line() {}
     Line(Point a,Point b) : s(a), e(b) {}
 }l[];
 int res[];
 int main()
 {
     int n;
     while (~scanf("%d", &n) && n)
     {
         for (int i = ; i <= n; i++){
             scanf("%lf%lf%lf%lf", &l[i].e.x, &l[i].e.y, &l[i].s.x, &l[i].s.y);
         }
         int cnt = ;
         for(int i = ; i <= n; i++)
         {
             bool flag = ;
             for (int j = i+; j <= n; j++)
             {
                 if(SegCross(l[i].e, l[i].s, l[j].e, l[j].s)){
                     flag = ; break;
                 }
             }
             if(flag) res[cnt++] = i;
         }

         printf("Top sticks: ");
         for (int i = ; i < cnt-; i++)
             printf("%d, ", res[i]);
         printf("%d.\n", res[cnt-]);
     }
 }