hdu 3668 几何题

就是考数学，考空间想象力，唉，数学还是不行啊，弄了两三个小时才勉强做出来……

/*
 * hdu3668/win.c
 * Created on: 2011-8-24
 * Author    : ben
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#define PI 3.1415926535

/**计算图形中那个特殊形体的体积的公式*/
double formular(double r, double t) {
    return r * r * t - t * t * t / 3;
}

void work() {
    int H, R;
    double ans, temp;
    while(scanf("%d%d", &R, &H) == 2) {
        ans = 2.0 * PI * R * R * H;
        if(2 * R <= H) {
            ans = ans - 8 * (formular(R, R) - formular(R, 0));
        }else {
            temp = sqrt(R * R - H * H / 4.0);
            ans = ans - 8 * (formular(R, R) - formular(R, temp)) - 2.0 * H * H * temp;
        }
        printf("%.4lf\n", ans);
    }
}

int main() {
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    work();
    return 0;
}