hdu_5734_Acperience

多校的题我还是贴官方题解的好，方便快捷，省事！！

 1 #include<cstdio>
 2 #include<cmath>
 3 #define F(i,a,b) for(int i=a;i<=b;i++)
 4 typedef long long ll;
 5 
 6 ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
 7 
 8 int main()
 9 {
10     int t,n,tp;
11     scanf("%d",&t);
12     while(t--)
13     {
14         ll fsum=0,sum=0;
15         scanf("%d",&n);
16         F(i,1,n)scanf("%d",&tp),sum+=tp>0?tp:-tp,fsum+=tp*tp;
17         sum*=sum,fsum*=n,fsum-=sum;
18         ll gc=gcd(fsum,n);
19         fsum/=gc,n/=gc;
20         printf("%lld/%d
",fsum,n);
21     }
22 }

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