C - FSANF两行数据，执行计算，打印结果，fscanf接下来两行，在一个循环中?

Question

我正在使用这个for循环从纬度和经度坐标文件中引入数据，然后将坐标转换为十进制度，将度转换为弧度，然后计算分离角度，并返回两个城市之间的距离。 我需要比较文件中的前两行，计算距离，打印结果，然后执行接下来的两行。 我已经完全按照我想要的方式得到了它，但有五个相同的 for 循环，只是每次调整循环控制参数。 有没有办法只用一个循环来实现这一点？

for(i=0;i<=ndata-9;i++)
{     
printf("n%-15s     %3.0f %4.1f %c     %3.0f %4.1f %c",cities[i].location,
cities[i].latdeg,cities[i].latmin,cities[i].directone,
cities[i].longdeg,cities[i].longmin,cities[i].directtwo);
fprintf(surface,"n%-15s     %3.0f %4.1f %c     %3.0f %4.1f %c",
cities[i].location,cities[i].latdeg,cities[i].latmin,
cities[i].directone,cities[i].longdeg,cities[i].longmin,
cities[i].directtwo);       
if(cities[i-1].directone=='N')
{
polarone=(90.0-(cities[i-1].latdeg+(cities[i-1].latmin/60.0)))*(pi/180.0);
}
else
{
polarone=(90.0+(cities[i-1].latdeg+(cities[i-1].latmin/60.0)))*(pi/180.0);
}
if(cities[i].directone=='N')
{
polartwo=(90.0-(cities[i].latdeg+(cities[i].latmin/60.0)))*(pi/180.0);
}
else
{
polartwo=(90.0+(cities[i].latdeg+(cities[i].latmin/60.0)))*(pi/180.0);
}
if(cities[i-1].directtwo=='W')
{
azimuthone=(cities[i-1].longdeg+(cities[i-1].longmin/60.0))*(pi/180.0);
}
else
{
azimuthone=(360.0-(cities[i-1].longdeg+(cities[i-1].longmin/60.0)))*(pi/180.0);
}
if(cities[i].directtwo=='W')
{   
azimuthtwo=(cities[i].longdeg+(cities[i].longmin/60.0))*(pi/180.0);
}
else
{
azimuthtwo=(360.0-(cities[i].longdeg+(cities[i].longmin/60.0)))*(pi/180.0);
}
angle=acos(cos(polarone)*cos(polartwo)+sin(polarone)*sin(polartwo)*cos(azimuthtwo-azimuthone));
distance=angle*radius;
}
printf("nDistance between the two cities = %6.1f milesn",distance); 
fprintf(surface,"nDistance between the two cities = %6.1f milesn", distance);

Answer 1

分而治之

!!(以下内容仅用于演示目的。我假设一切都是双重的，城市有类型结构城市。如有必要，请更改类型。另外，我没有调试它。

const double deg_to_rad = pi/180, half_pi = pi/2, two_pi = pi*2;
inline double RadFromDeg(double degrees, double minutes) {
return (degrees+minutes/60)*deg_to_rad;
}
// not sure if we really need inline here
inline void ObtainPolarAzimuth(double* polar, double* azimuth, struct City* city) {
double temp = RadFromDeg(city->latdeg, city->latmin);
if (city->directone == 'N')
*polar = half_pi - temp;
else
*polar = half_pi + temp;
// ... blablabla longdeg blablabla longmin blablabla *azimuth
}

// ... 
ObtainPolarAzimuth(*polar1, *azimuth1, city[i-1]); 
ObtainPolarAzimuth(*polar2, *azimuth2, city[i]);
// ... blablabla angle blablabla cos blablabla sin

另外，恕我直言，最好写direct1和direct2而不是directone和directtwo.