模板–判断两条线段是否相交–计算几何quequeheiya的博客-

模板–判断两条线段是否相交–计算几何；

1.两个结构体表示的是该条线段的A,B两个端点；

 const int maxa=1e2+10; const double pi=0.00000001; struct nodea{  int x,y; }a[maxa]; struct nodeb{  int x,y; }b[maxa]; bool check(nodea a,nodeb b,nodea c,nodeb d){     if(!(min(a.x,b.x)<=max(c.x,d.x)  &&min(c.y,d.y)<=max(a.y,b.y)  &&min(c.x,d.x)<=max(a.x,b.x)  &&min(a.y,b.y)<=max(c.y,d.y))) return false;      double u,v,w,z;     u=(c.x-a.x)*(b.y-a.y)-(b.x-a.x)*(c.y-a.y);     v=(d.x-a.x)*(b.y-a.y)-(b.x-a.x)*(d.y-a.y);     w=(a.x-c.x)*(d.y-c.y)-(d.x-c.x)*(a.y-c.y);     z=(b.x-c.x)*(d.y-c.y)-(d.x-c.x)*(b.y-c.y);     return (u*v<=pi&&w*z<=pi); }

2.一个结构体表示的是该条线段的A,B两个端点,用于判断线段A,B是否相交；

 const int maxa=1e2+10; const double pi=1e-8; const int inf=0x3f3f3f3f; int n; struct node{  int x1,y1;  int x2,y2; }a[maxa]; bool check(node &a,node &b){  if(!(min(a.x1,a.x2)<=max(b.x1,b.x2)  &&min(b.y1,b.y2)<=max(a.y1,a.y2)  &&min(b.x1,b.x2)<=max(a.x1,a.x2)  &&min(a.y1,a.y2)<=max(b.y1,b.y2))) return false;  double u,v,w,z;     u=(b.x1-a.x1)*(a.y2-a.y1)-(a.x2-a.x1)*(b.y1-a.y1);     v=(b.x2-a.x1)*(a.y2-a.y1)-(a.x2-a.x1)*(b.y2-a.y1);     w=(a.x1-b.x1)*(b.y2-b.y1)-(b.x2-b.x1)*(a.y1-b.y1);     z=(a.x2-b.x1)*(b.y2-b.y1)-(b.x2-b.x1)*(a.y2-b.y1);     return (u*v<=pi&&w*z<=pi); } 

题目链接：

传送门ZOJ–1648

传送门UVA–191