找到行列之间的关系就行

#include<iostream>
using namespace std;
const int N = 12;
double a[N][N];
int main()
{
    char c;
    cin>>c;
    for(int i = 0;i<12;i++)
        for(int j = 0;j<12;j++)
            cin>>a[i][j];

    double sum = 0.0,cnt = 0,avg = 0.0;
    if(c=='S')
    {
        for(int i = 0;i<=4;i++)
        {
            for(int j = i+1;j<11-i;j++)
            {
                sum+=a[i][j];
            }
        }
        cout<<sum<<endl;
    }
    else
    {
        for(int i = 0;i<=4;i++)
        {
            for(int j = i+1;j<11-i;j++)
            {
                sum+=a[i][j];
                cnt++;
            }
        }
        avg = sum/cnt;
        cout<<avg<<endl;
    }

    return 0;
}