#include <bits/stdc++.h>
using namespace std;
int main()
{
    int x;
    double sum=0,num=0;
    for(int i=1;i<=9999999;i++)
    {
        cin >> x;
        if(x==0)
        {
            break;
        }
        sum+=x;
        num++;
    }
    cout << fixed << setprecision(1);
    cout << sum/num << " ";
    sum=0;
    num=0;
    for(int i=1;i<=9999999;i++)
    {
        cin >> x;
        if(x==0)
        {
            break;
        }
        sum+=x;
        num++;
    }
    cout << fixed << setprecision(1);
    cout << sum/num;
}

很简单，只需要逐个输入累加求和，用ans1记录男生人数，ans2记录女生人数，在计算平均成绩，输出即可，至于代码嘛，凑合着看吧！

$Ac$ $Code$

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int x, ans1 = 0,ans2 = 0;
    double avg1 = 0,avg2 = 0;
    while(cin>>x)
    {
        if(x==0)
            break;
        ans1++;
        avg1+=x;
    }
    cout<<fixed<<setprecision(1)<<avg1 / (ans1*1.0)<<" ";
    while(cin>>x)
    {
        if(x==0)
            break;
        ans2++;
        avg2+=x;
    }
    cout<<fixed<<setprecision(1)<<avg2 / (ans2*1.0);
    return 0;
}