提出 #14835675

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ソースコード 拡げる

#include<cstdio>
int N,K,P,fac[210],ifac[210];
long long inv(int a,int p=P){return a==1?1:(1+p*(a-inv(p%a,a)))/a%p;}
int C(int n,int m){return m<0||m>n?0:1ll*fac[n]*ifac[m]%P*ifac[n-m]%P;}
int calc(int a,int b,int k){
	if(a>k+1||b>k)return 0;
	int x=a>k,s=0;
	for(int i=k+1,j=b;j<=a+b-x;i+=k*2+3-a-b,j+=k*2+3-a-b)s=((s+P-C(a+b-x,i))%P+C(a+b-x,j))%P;
	for(int i=a+b-k-2,j=a+b*2-k*2-3;i>=0;i-=k*2+3-a-b,j-=k*2+3-a-b)s=((s+P-C(a+b-x,i))%P+C(a+b-x,j))%P;
	if(a+b-1<=k)s=(s+P-1)%P;
	if(a+b<=k)s=(s+P-1)%P;
	return s;
}
int main(){
	scanf("%d%d%d",&N,&K,&P);
	for(int i=*fac=1;i<=N;i++)fac[i]=1ll*fac[i-1]*i%P;
	ifac[N]=inv(fac[N]);
	for(int i=N;i;i--)ifac[i-1]=1ll*ifac[i]*i%P;
	int s=K>=N-1?fac[N]:0;
	for(int i=0;i<=N-3&&K-i>=(N-i)/2;i++){
		int t=K<N-2?0:N-i-2;
		for(int j=1;j<=K-i&&j<N-i-1;j++)t=(t+calc(j,N-i-j-1,K-i))%P;
		s=(s+1ll*fac[N]*ifac[N-i]%P*fac[N-i-1]%P*t)%P;
	}
	printf("%d\n",s);
}

提出情報

ジャッジ結果