给大家发个精简版，在这段代码中，我使用了 cmath 库中的 M_PI 常量和 ceil() 函数~

#include <iostream>
#include <cmath>
using namespace std;
int main()
{
    int h, r;
    cin >> h >> r;
    double v = M_PI * r * r * h; // 求小圆桶的体积
    int n = ceil(20000.0 / v);  // 上取整求需要的桶数
    cout << n << endl;
    return 0;
}

经典数学问题不必多说了吧……^_^

#include <iostream>
using namespace std;
int main(){
    int h,r;
    cin>>h>>r;
    cout<<(int)(20*1000/(3.141592653589793238462643*r*r*h)+1);
}

#include <stdio.h>
int main()
{
	int h, r, x, v;
	double PI = 3.14159;
	scanf("%d %d",&h,&r);
	v = PI * r * r * h;
	x = 20000 / v;
	printf("%d",(int)(x)+1);
	return 0;
}

#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
    int h,r;
    cin >> h >> r;
    int c;
    c =  3.14159 * r * r * h ;
    int d;
    d = 20 * 1000 / c;
    cout << d + 1 << endl;
    
}

这里的PI我用了前80位的

# include <bits/stdc++.h>

using namespace std;
const double PI=3.141592653589793238462643383279502884197169399375105820979230781640628620899;
int main(){
	int h,r,d,ans;
	cin>>h>>r;
	d=r*r*PI*h;
	ans=20*1000/d;
	cout<<ans+1<<endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a,b;
    cin>>a>>b;
    double v=3.14159*b*b*a;
    cout<<ceil(20.0*1000/v)<<endl;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a,b;
    cin>>a>>b;
    double v=3.14159*b*b*a;
    cout<<ceil(20.0*1000/v)<<endl;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a,b;
    cin>>a>>b;
    double v=3.14159*b*b*a;
    cout<<ceil(20.0*1000/v)<<endl;
    return 0;
}