杭电5645

#include <iostream>#include <cstdio>using namespace std;int main(){int t,n,i,j;int a[310],num;scanf("%d",&t);while(t--){num=0;scanf("%d",&n);for(i=1;i<=n;i++)scanf("%d",&a[i]);for(i=1;i<=n;i++){for(j=1;j<=n;j++){if(a[i]>a[j])num++;}}printf("%.6f\n",num/(n*(n-1.0)));}return 0;}