CFglobal21

标签：CFglobal21 int ll iv ij jc

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 
 4 typedef long long ll;
 5 const ll N=1e6+3,H=1e9+7;
 6 ll n,a[N],jc[N],ij[N],iv[N];
 7 void Pre()
 8 {
 9     jc[0]=ij[0]=iv[0]=iv[1]=1;
10     for(int i=2;i<N;i++)iv[i]=H-(H/i)*iv[H%i]%H;
11     for(int i=1;i<N;i++)
12         jc[i]=jc[i-1]*i%H,ij[i]=ij[i-1]*iv[i]%H;
13 }
14 ll C(ll n,ll m)
15 {
16     if(n<0||m<0||n<m)return 0;
17     return jc[n]*ij[m]%H*ij[n-m]%H;
18 }
19 void Solve()
20 {
21     cin>>n;ll s=0;Pre();
22     for(int i=1;i<=n+1;i++)cin>>a[i];
23     for(int i=1;i<=n+1;i++)s=(s+C(i+a[i]-1,i))%H;
24     cout<<s<<endl;
25 }
26 int main()
27 {
28     int T;T=1;
29     while(T--)Solve();
30     return 0; 
31 }

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标签：CFglobal21,int,ll,iv,ij,jc
From： https://www.cnblogs.com/Hanghang007/p/17069447.html