10897 - Travelling Distance/10897.2.cpp

   1 /*
   2   Accepted
   3
   4   This is a cleaner version of 10897.cpp
   5  */
   6 using namespace std;
   7 #include <iostream>
   8 #include <cmath>
   9
  10 const long double rho = 6371.01;//km
  11 const long double pi = 2*acos(0.0);
  12
  13 struct Vector{
  14   //A geometrical vector
  15   long double x, y, z;
  16   long double dot(const Vector &t) const{
  17     return x*t.x + y*t.y + z*t.z;
  18   }
  19   long double mag() const{
  20     return sqrt(x*x + y*y + z*z);
  21   }
  22 };
  23
  24 struct point{
  25   //A point in spherical coordinates
  26   //assuming rho = 1
  27   long double phi, theta;
  28   Vector toVector() const{
  29     Vector v;
  30     v.x = sin(phi)*cos(theta);
  31     v.y = sin(phi)*sin(theta);
  32     v.z = cos(phi);
  33     return v;
  34   }
  35 };
  36
  37 istream& operator >> (istream &in, point &p){
  38   long double a, b, c, d, e, f;
  39   char X, Y;
  40   in >> a >> b >> c >> X >> d >> e >> f >> Y;
  41
  42   long double latitude, longitude;
  43   latitude = (a + b/60.0 + c/3600.0);
  44   longitude = (d + e/60.0 + f/3600.0);
  45
  46   p.phi = 90 + latitude * (X == 'N' ? -1.0 : 1.0);
  47   p.theta = longitude * (Y == 'E' ? -1.0 : 1.0);
  48
  49   p.phi *= pi/180.0, p.theta *= pi/180.0; //"radianize"
  50   return in;
  51 }
  52
  53 long double dist(point &a, point &b){
  54   //Convert shperical coordinates to rectangular coordinates...
  55   Vector va = a.toVector(), vb = b.toVector();
  56   //find angle between the two vectors...
  57   long double angle = acos(va.dot(vb) / (va.mag()*vb.mag()) );
  58   //calculate length of circle arc... (rho is the radius)
  59   return rho * angle;
  60 }
  61
  62 int main(){
  63   int n;
  64   for (scanf("%d", &n); n--; ){
  65     point a, b;
  66     cin >> a >> b;
  67     cout.precision(2);
  68     cout << fixed << dist(a, b) << endl;
  69   }
  70   return 0;
  71 }