UVa11817

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=2917

模版，测地线距离和直线距离之差

精度问题令人头疼！

 

#include<cstdio>

#include<cmath>

using namespace std;

const double R = 6371009;



double torad(double deg) {

  return deg/180 * M_PI;

}



void get_coord(double lat, double lng, double& x, double& y, double& z) {

  lat = torad(lat);

  lng = torad(lng);

  x = R*cos(lat)*cos(lng);

  y = R*cos(lat)*sin(lng);

  z = R*sin(lat);

}



double sqr(double x) { return x*x; }



double dist(double x1, double y1, double z1, double x2, double y2, double z2) {

  return sqrt(sqr(x1-x2)+sqr(y1-y2)+sqr(z1-z2));

}



int main() {

  int T;

  double lat1, lng1, lat2, lng2;

  double x1, y1, z1, x2, y2, z2;

  scanf("%d", &T);

  while(T--) {

    scanf("%lf%lf%lf%lf", &lat1, &lng1, &lat2, &lng2);

    get_coord(lat1, lng1, x1, y1, z1);

    get_coord(lat2, lng2, x2, y2, z2);

    double d = dist(x1, y1, z1, x2, y2, z2);

    double d2 = 2*asin(d/(2*R))*R;

    printf("%.0lf\n", d2-d);

  }

  return 0;

}