C++ 代码
#include<cstdio>
const int n = 12;
int main(){
int counter = 0;
char f;
double sum = 0, m[n][n];
scanf("%c", &f);
for(int i = 0; i < n; i++){
for (int j = 0; j < n; j++) scanf("%lf", &m[i][j]);
}
for(int i = 0; i < n; i++){
for (int j = i+1; j <= n-2-i; j++) sum += m[i][j], counter++;
}
if(f == 'S') printf("%.1lf", sum);
else if (f == 'M') printf("%.1lf", sum / counter);
return 0;
}