hdu_5734_Acperience

题目连接：hdu_5734_Acperience

多校的题我还是贴官方题解的好，方便快捷，省事！！

 #include<cstdio>
 #include<cmath>
 #define F(i,a,b) for(int i=a;i<=b;i++)
 typedef long long ll;

 ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}

 int main()
 {
     int t,n,tp;
     scanf("%d",&t);
     while(t--)
     {
         ll fsum=,sum=;
         scanf("%d",&n);
         F(i,,n)scanf("%d",&tp),sum+=tp>?tp:-tp,fsum+=tp*tp;
         sum*=sum,fsum*=n,fsum-=sum;
         ll gc=gcd(fsum,n);
         fsum/=gc,n/=gc;
         printf("%lld/%d\n",fsum,n);
     }
 }