Gym - 101810E ACM International Collegiate Programming Contest (2018)

bryce1010模板
http://codeforces.com/gym/101810

#include<bits/stdc++.h>
using namespace std;

#define ll long long 

const ll maxn = 1e5 + 5;
const ll mod = 1e9+7;

ll n;
ll p[maxn];
ll vis[maxn];

int main()
{
    ll t;
    scanf("%lld",&t);
    ll pre;
    while(t--)
    {
        scanf("%lld",&n);
        pre = 1;
        for(int i=1;i<=n;i++)
        {
            scanf("%lld",&p[i]);
        }

        fill(vis,vis+1+n,1);
        for(int i=1;i<=n;i++)
        {
            vis[i] = pre*vis[i]%mod;
            pre = p[i]*pre%mod;
        }
        vis[0] = n*pre%mod;
        pre = 1;
        for(int i=n;i>=1;i--)
        {
            vis[i] = pre*vis[i]%mod;
            pre = p[i]*pre%mod;
        }

        ll ans = vis[0];
        for(int i=1;i<=n;i++)
        {
            ans = (mod+ans-vis[i])%mod;
        }
        printf("%lld\n",ans);
    }
    return 0;
}