lib/Documentation/docs-sonyckson/1075.cpp

   1 // THREAD IN THE SPACE....
   2
   3 #include <cstdio>
   4 #include <cmath>
   5 #include <cstdlib>
   6 typedef struct{
   7         double x, y , z;
   8 }point;
   9 void read(point & A){
  10         scanf("%lf %lf %lf", &(A.x), &(A.y), &(A.z));
  11 }
  12 double dist(point p1, point p2){
  13         return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y) + (p1.z-p2.z)*(p1.z-p2.z));
  14 }
  15 double Pi;
  16 double acos1(double x){
  17         if( x > 1 ) x = 1;
  18         if( x < -1 ) x = -1;
  19         double res = acos(x);
  20         while( res < 0.0 ) res += 2.0*Pi;
  21         if( res >= Pi ) res = 2.0*Pi - res;
  22         return res;
  23 }
  24
  25
  26 int main(){
  27         int i,j ,k;
  28         Pi = acos(-1.0);
  29         point A, B, C;
  30         read(A), read(B), read(C);
  31         if( A.x == B.x && A.y == B.y && A.z == B.z ){
  32                 printf("0.00\n");
  33                 return 0;
  34         }
  35         double R;
  36         scanf("%lf", &R);
  37         double dab, dbc, dac;
  38         dab = dist(A, B);
  39         dbc = dist(B, C);
  40         dac = dist(A, C);
  41         double s = (dab+dbc+dac)/2.0;
  42         double area = sqrt(s*(s-dac)*(s-dbc)*(s-dab));
  43         double alt = (area*2.0)/dab;
  44         if( fabs(alt-R) < 1e-7 || alt > R ){
  45                 printf("%.2lf\n", dab);
  46                 return 0;
  47         }
  48         if (((dac*dac + 1e-7) >= (dab *dab+ dbc*dbc)) || ((dbc*dbc+1e-7) >= dab*dab+ dac*dac)){
  49
  50                 printf("%.2lf\n", dab);
  51                 return 0;
  52         }
  53         double l1, l2;
  54         l1 = sqrt(dac*dac - R * R);
  55         l2 = sqrt(dbc*dbc - R * R);
  56         double angleacb, anglel1ca, anglel2cb;
  57         double a, b, c;
  58         c = dab;
  59         b = dbc, a = dac;
  60         angleacb = acos1((c*c-a*a-b*b)/(-2.0*a*b));
  61
  62         c = l1, b = R, a = dac;
  63         anglel1ca = acos1((c*c-a*a-b*b)/(-2.0*a*b));
  64
  65         c = l2; a = dbc;
  66         anglel2cb =  acos1((c*c-a*a-b*b)/(-2.0*a*b));
  67
  68         double alfa = angleacb - anglel1ca - anglel2cb;
  69
  70         double di = (Pi*(R+R)) * alfa / (2.*Pi);
  71
  72         printf("%.2lf\n",( di + l1 + l2 ));
  73         return 0;
  74 }