> #include<stdio.h>
> #include<math.h>
> #define MAX 16
> #define PI 3.1415926535
> struct vector { float x,y,z; };
> void rotate(struct vector *x0,struct vector *y0,struct vector *z0,float a,int b) {
>  struct vector x,y,z;
>  float C=cos(PI*a/180);
>  float S=sin(PI*a/180);
>  if (b) {
>   x=*x0;
>   y.x=y0->x*C+z0->x*S;
>   y.y=y0->y*C+z0->y*S;
>   y.z=y0->z*C+z0->z*S;
>   z.x=z0->x*C-y0->x*S;
>   z.y=z0->y*C-y0->y*S;
>   z.z=z0->z*C-y0->z*S;
>   }
>  else {
>   y=*y0;
>   x.x=x0->x*C-z0->x*S;
>   x.y=x0->y*C-z0->y*S;
>   x.z=x0->z*C-z0->z*S;
>   z.x=z0->x*C+x0->x*S;
>   z.y=z0->y*C+x0->y*S;
>   z.z=z0->z*C+x0->z*S;
>   }
>  *x0=x; *y0=y; *z0=z;
>  }
> float sqr(float p) {
>  return p*p;
>  }
> float troj(struct vector *x,struct vector *y,struct vector *z) {
>  float S=0;
>  S+=sqr((z->x-x->x)*(z->y-y->y)-(z->x-y->x)*(z->y-x->y));
>  S+=sqr((z->z-x->z)*(z->y-y->y)-(z->z-y->z)*(z->y-x->y));
>  S+=sqr((z->x-x->x)*(z->z-y->z)-(z->x-y->x)*(z->z-x->z));
>  return S/2;
>  }
> #define skal(X2,X1,Z) ((X2->x-X1->x)*Z->x+(X2->y-X1->y)*Z->y+(X2->z-X1->z)*Z->z)
> int intersect(struct vector *x1,struct vector *x2,struct vector *y1,struct vector *y2) {
>  struct vector w;
>  float X,Y,W,A,B,C,D,E;
>  if ((fabs(x1->x-x2->x)<0.000001)&&(fabs(x1->y-x2->y)<0.000001)&&(fabs(x1->z-x2->z)<0.000001)) return 0;
>  if ((fabs(y1->x-y2->x)<0.000001)&&(fabs(y1->y-y2->y)<0.000001)&&(fabs(y1->z-y2->z)<0.000001)) return 0;
>  w.x=(x2->y-x1->y)*(y2->z-y2->z)-(x2->z-x1->z)*(y2->y-y2->y);
>  w.y=-(x2->x-x1->x)*(y2->z-y2->z)+(x2->z-x1->z)*(y2->x-y1->x);
>  w.z=(x2->x-x1->x)*(y2->y-y2->y)-(x2->y-x1->y)*(y2->x-y1->x);
>  W=sqrt(w.x*w.x+w.y*w.y+w.z*w.z);
>  if (W<0.000001) {
>   /* parallel */
>   W=troj(x1,x2,y1);
>   W=W*2/sqrt(sqr(x2->x-x1->x)+sqr(x2->y-x1->y)+sqr(x2->z-x1->z));
>   if (W>0.001) return 0; 
>   }
>  else {
>   if ((fabs(x2->x-y1->x)<0.000001)&&(fabs(x2->y-y1->y)<0.000001)&&(fabs(x2->z-y1->z)<0.000001)) return 0;
>   w.x/=W;
>   w.y/=W;
>   w.z/=W;
>   X=w.x*x1->x+w.y*x1->y+w.z*x1->z;
>   Y=w.x*y1->x+w.y*y1->y+w.z*y1->z;
>   if (fabs(Y-X)>0.001) return 0; 
>   }
>  A=skal(x2,x1,x1);
>  B=skal(x2,x1,x2);
>  C=skal(x2,x1,y1);
>  D=skal(x2,x1,y2);
>  if (A>B) { E=A; A=B; B=E; }
>  if (C>D) { E=C; C=D; D=E; }
>  if ((B<C+0.00001)||(D<A+0.00001)) return 0;
>  A=skal(y2,y1,x1);
>  B=skal(y2,y1,x2);
>  C=skal(y2,y1,y1);
>  D=skal(y2,y1,y2);
>  if (A>B) { E=A; A=B; B=E; }
>  if (C>D) { E=C; C=D; D=E; }
>  if ((B<C+0.00001)||(D<A+0.00001)) return 0;
>  return 1;
>  }
> float length[MAX];
> float angle[MAX];
> struct vector poloha[MAX];
> int m,n;
> int i,j;
> struct vector x,y,z;
> 
> int main() {
>  scanf("%d",&n);
>  for (m=1; n>0; m++) {
>   printf("Case %d: ",m);
>   for (i=0; i<n; i++) scanf("%f",&length[i]);
>   for (i=0; i<n; i++) scanf("%f",&angle[i]);
>   x.x=y.y=z.z=1;
>   x.y=x.z=y.x=y.z=z.x=z.y=0;
>   poloha[0].x=poloha[0].y=poloha[0].z=0;
>   for (i=0; i<n; i++) {
>    rotate(&x,&y,&z,angle[i],i&1);
>    poloha[i+1].x=poloha[i].x+z.x*length[i];
>    poloha[i+1].y=poloha[i].y+z.y*length[i];
>    poloha[i+1].z=poloha[i].z+z.z*length[i];
>    }
>   for (i=0; i<n; i++) {
>    if (poloha[i+1].z<0) {
>     printf("servo %d attempts to move arm below floor\n",i+1);
>     break;
>     }
>    for (j=0; j<i; j++)
>     if (intersect(&poloha[j],&poloha[j+1],&poloha[i],&poloha[i+1])) {
>      printf("servo %d causes link collision\n",i+1);
>      break;
>      }
>    if (j!=i) break;  
>    }
>   if (i==n) printf("robot's hand is at (%.3f,%.3f,%.3f)\n",poloha[n].x,poloha[n].y,poloha[n].z);
>   scanf("%d",&n);
>   }
>  return 0;
>  }
> 
> 
> 
> 
> 
> 
> 
>  w.x=(x2->y-x1->y)*(y2->z-y2->z)-(x2->z-x1->z)*(y2->y-y2->y);
>  w.y=-(x2->x-x1->x)*(y2->z-y2->z)+(x2->z-x1->z)*(y2->x-y1->x);
>  w.z=(x2->x-x1->x)*(y2->y-y2->y)-(x2->y-x1->y)*(y2->x-y1->x);
> 
> 这里y2->z-y2->z和 y2->y-y2->y明显是0  标程似乎把变量打错了 测了一组数据:
> X1(0.0 0.0 9.2) Y1(0 -20.398618 96.857837) X2(0.212132 -20.446698 97.064449) Y2(4.242641 -19.533178 93.138830)
> X1Y1与X2Y2是不相交的，标程判成了相交
> 
> 希望管理员能改一下数据
> 
顶，同觉得标称错，数据错！