蒟蒻求助

40分代码

#include<bits/stdc++.h>
using namespace std;

int main(){
	double r, pi=3.1415926;
    cin >> r;
    cout << fixed << setprecision(4) << 2*r << " ";
	cout << fixed << setprecision(4) << 2*r*pi << " ";
	cout << fixed << setprecision(4) << pi*r*r << " " << endl;
	return 0;
}

100分代码

#include<bits/stdc++.h>
using namespace std;

int main(){
	double r, pi=3.14159;
    cin >> r;
    cout << fixed << setprecision(4) << 2*r << " ";
	cout << fixed << setprecision(4) << 2*r*pi << " ";
	cout << fixed << setprecision(4) << pi*r*r << " " << endl;
	return 0;
}