UVa 10897 - Travelling Distance

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题目：给你地球上两点的经度和纬度，计算球面最近距离。

分析：计算几何、大地坐标系。利用公式计算连点间距离，再转化成弧长即可。

d = r*sqrt(2-2*(cos(lat1)*cos(lat2)*cos(lon1-lon2)+sin(lat1)*sin(lat2))) （推导见11817）

弧长：s = 2*asin(d/(2*r))*r

#include <stdio.h>#include <stdlib.h>#include <math.h>int main(){double r = 6371.01;double p = acos(-1.0);int    n;char   ch;double a,b,c,A1,B1,A2,B2;while ( scanf("%d",&n) != EOF )while ( n -- ) {scanf("%lf%lf%lf %c",&a,&b,&c,&ch);A1 = a+b/60.0+c/3600.0;if ( ch == 'S' ) A1 *= -1;A1 *= p/180.0;scanf("%lf%lf%lf %c",&a,&b,&c,&ch);B1 = a+b/60.0+c/3600.0;if ( ch == 'W' ) B1 *= -1;B1 *= p/180.0;scanf("%lf%lf%lf %c",&a,&b,&c,&ch);A2 = a+b/60.0+c/3600.0;if ( ch == 'S' ) A2 *= -1;A2 *= p/180.0;scanf("%lf%lf%lf %c",&a,&b,&c,&ch);B2 = a+b/60.0+c/3600.0;if ( ch == 'W' ) B2 *= -1;B2 *= p/180.0;double d = r*sqrt(2-2*(cos(A1)*cos(A2)*cos(B1-B2)+sin(A1)*sin(A2)));printf("%.2lf\n",2*asin(d/(2*r))*r);}return 0;}