数学专项counting：LA 5846

#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdio>
using namespace std;
#define M 1010
int n;
int a[M];
int main()
{
freopen("in.txt","r",stdin);
int T;
cin>>T;
while(T--)
{
memset(a,0,sizeof(a));
cin>>n;
int c;
for(int i=n;i>1;i--)
{
for(int j=1;j<i;j++)
{
cin>>c;
if(c)
{
a[n-i+1]++;
a[n-i+j+1]++;
}
}
}
int ans=0;
for(int i=1;i<=n;i++)
ans+=a[i]*(n-1-a[i]);
ans=n*(n-1)*(n-2)/6-ans/2;
cout<<ans<<endl;
}
return 0;
}