周一（PTA简单题）例

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{   int N,i,sex,b=0,g=0;float score,aver1,aver2,aver3,b1=0.0,g1=0.0;
    cin>>N;
    for(i=0;i<N;i++)
    {cin>>sex;cin>>score;
    if(sex==1){b+=1;b1+=score;}
     else{g+=1;g1+=score;}
    }
 aver1=(b1+g1)/N;
 if(b!=0&&g!=0)
 {
 aver2=b1/b;
 aver3=g1/g;
     cout<<setiosflags(ios::fixed)<<setprecision(1)<<aver1<<" "<<setiosflags(ios::fixed)<<setprecision(1)<<aver2<<" "<<setiosflags(ios::fixed)<<setprecision(1)<<aver3;
 }
 if(b==0&&g!=0)
 {
     aver3=g1/g;
     cout<<setiosflags(ios::fixed)<<setprecision(1)<<aver1<<" "<<"X"<<" "<<setiosflags(ios::fixed)<<setprecision(1)<<aver3;
 }
 if(b!=0&&g==0)
 { aver2=b1/b;
 cout<<setiosflags(ios::fixed)<<setprecision(1)<<aver1<<" "<<setiosflags(ios::fixed)<<setprecision(1)<<aver2<<" "<<"X";}
 return 0;
}