Submission #859503

#	Time	Username	Problem	Language	Result	Execution time	Memory
859503		lucri	NoM (RMI21_nom)	C++17	100 / 100	92 ms	63252 KiB

Main

#include <bits/stdc++.h>
#define MOD 1000000007
using namespace std;
long long n,m,d[2010][2010],r[2010],fact[4010],im[4010],ans,comb[2010][2010];
long long putere(long long a,long long b)
{
    if(b==0)
        return 1;
    long long m=putere(a,b/2);
    m*=m;
    m%=MOD;
    if(b%2)
    {
        m*=a;
        m%=MOD;
    }
    return m;
}
void factorial()
{
    fact[0]=1;
    for(int i=1;i<=4000;++i)
        fact[i]=(fact[i-1]*i)%MOD;
    for(int i=0;i<=4000;++i)
        im[i]=putere(fact[i],MOD-2);
}
/*long long combinari(long long n,long long m)
{
    long long ans=fact[n];
    ans*=putere(fact[m],MOD-2);
    ans%=MOD;
    ans*=putere(fact[n-m],MOD-2);
    ans%=MOD;
    return ans;
}*/
long long aranjamente(long long n,long long m)
{
    long long ans=fact[n];
    ans*=im[n-m];
    ans%=MOD;
    return ans;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    factorial();
    cin>>n>>m;
    for(int i=0;i<=n;++i)
    {
        comb[i][0]=comb[i][i]=1;
        for(int j=1;j<i;++j)
            comb[i][j]=(comb[i-1][j-1]+comb[i-1][j])%MOD;
    }
    d[0][0]=1;
    for(int i=1;i<=2*n;++i)
        ++r[i%m];
    r[m]=r[0];
    for(int j=0;j<=n;++j)
        for(int i=1;i<=m;++i)
            for(int k=0;2*k<=r[i]&&k<=j;++k)
            {
                d[i][j]+=comb[j][k]*aranjamente(r[i],2*k)%MOD*d[i-1][j-k]%MOD;
                if(d[i][j]>=MOD)
                    d[i][j]-=MOD;
            }
    for(int i=1;i<=n;++i)
    {
        ans+=((i-1)%2*2-1)*d[m][i]%MOD*fact[2*n-2*i]%MOD*comb[n][i]%MOD;
        if(ans>=MOD)
            ans-=MOD;
        if(ans<0)
            ans+=MOD;
    }
    ans+=fact[2*n];
    if(ans>=MOD)
        ans-=MOD;
    cout<<ans;
    return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 18 / 18
• Subtask 5: 48 / 48