luogu 5505 [JSOI2011]分特产 广义容斥

code:

#include <bits/stdc++.h>
#define N 10005
#define LL long long
using namespace std;
const LL mod=1000000007;
void setIO(string s)
{
    string in=s+".in";
    string out=s+".out";
    freopen(in.c_str(),"r",stdin);
}
int a[N];
LL fac[N],inv[N],f[N],g[N];
LL qpow(LL x,LL y)
{
    LL tmp=1ll;
    for(;y;y>>=1,x=x*x%mod)
        if(y&1) tmp=tmp*x%mod;
    return tmp;
}
LL Inv(LL x) { return qpow(x,mod-2); }
LL C(int x,int y)
{
    return fac[x]*inv[y]%mod*inv[x-y]%mod;
}
int main()
{
    // setIO("input");
    int i,j,n,m;
    fac[0]=inv[0]=1ll;
    for(i=1;i<N;++i) fac[i]=fac[i-1]*1ll*i%mod,inv[i]=Inv(fac[i]);
    scanf("%d%d",&n,&m);
    for(i=1;i<=m;++i) scanf("%d",&a[i]);
    for(i=0;i<=n;++i)
    {
        f[i]=C(n,i);
        for(j=1;j<=m;++j) (f[i]=f[i]*C(a[j]+n-i-1,n-i-1)%mod)%=mod;
    }
    for(i=0;i<=n;++i)
    {
        (g[0]+=qpow(-1,i)*f[i]%mod+mod)%=mod;
    }
    printf("%lld\n",g[0]);
    return 0;
}

原文地址：https://www.cnblogs.com/guangheli/p/11734770.html