这才是正确的题解

#include <bits/stdc++.h>
using namespace std;
int main(){
double r;
cin>>r;
printf("%.4f",r2);//直径
cout<<" ";
printf("%.4f",23.14159r);//周长
cout<<" ";
printf("%.4f",rr*3.14159);//面积
return 0;
}