uva 11817 - Tunnelling the Earth(几何)

题目链接：uva 11817 - Tunnelling the Earth

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;const double R = 6371009;const double pi = 4 * atan(1.0);struct Point {double x, y, z;}p[2];Point getPoint(double a, double b) {double z = R * sin(a);double t = R * cos(a);double x = t * cos(b);double y = t * sin(b);return (Point){x, y, z};}double distant(Point a, Point b) {double x = a.x - b.x;double y = a.y - b.y;double z = a.z - b.z;return sqrt(x * x + y * y + z * z);}int main () {int cas;scanf("%d", &cas);while (cas--) {double a, b;for (int i = 0; i < 2; i++) {scanf("%lf%lf", &a, &b);p[i] = getPoint(a / 180 * pi, b / 180 * pi);}double D = distant(p[0], p[1]);double tha = 2 * asin(D / (2 * R));double L = R * tha;printf("%.0lf\n", L - D);}return 0;}