https://ac.nowcoder.com/acm/contest/373/E

题解：

参考文章：https://blog.csdn.net/luyehao1/article/details/86583384

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
double t,n,m,k,q,x,y,z,r,x2,y2,z2,r2;
double ans,cnt,flag,temp;
int a[N];
char str;
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&x,&y,&z,&r,&x2,&y2,&z2,&r2);
    double d=sqrt((x-x2)*(x-x2)+(y-y2)*(y-y2)+(z-z2)*(z-z2));
    if(r>r2){
        swap(r,r2);
        swap(x,x2);
        swap(y,y2);
        swap(z,z2);
    }
    if (d >= r + r2) {
        ans=(4.0 / 3)*PI*(r*r*r+r2*r2*r2);
    }else if (d + r <= r2) {
        ans = (4.0 / 3)*PI*r2*r2*r2;
    }else {
        double co = (r2*r2 + d * d - r*r) / (2.0*d*r2);
        double h = r2*(1 - co);
        ans += (1.0 / 3)*PI*(3.0*r2 - h)*h*h;
        co = (r*r + d * d - r2*r2) / (2.0*d*r);
        h = r*(1 - co);
        ans += (1.0 / 3)*PI*(3.0*r - h)*h*h;
        ans=(4.0 / 3)*PI*(r*r*r+r2*r2*r2)-ans;
    }
    printf("%.7lf\n",  ans);
    //cout << "Hello world!" << endl;
    return 0;
}