[Polya] BZOJ 1488 图的同构

来源：互联网发布：php三元运算符编辑：程序博客网时间：2024/06/05 19:31

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http://blog.csdn.net/wzq_qwq/article/details/48035455

#include<cstdio>#include<cstdlib>#include<cmath>#include<algorithm>#define P 997using namespace std;inline int Gcd(int a,int b){if (a<b) return Gcd(b,a);return !b?a:Gcd(b,a%b);}inline int Pow(int a,int b){int ret=1;for (;b;b>>=1,a=a*a%P)if (b&1)(ret*=a)%=P;return ret;}const int maxn=65;int fac[maxn+5],inv[maxn+5];inline void Pre(){fac[0]=1;for (int i=1;i<=maxn;i++)(fac[i]=i*fac[i-1])%=P;inv[1]=1;for (int i=2;i<=maxn;i++)(inv[i]=(P-P/i)*inv[P%i])%=P;inv[0]=1;for (int i=1;i<=maxn;i++)(inv[i]*=inv[i-1])%=P;}int n,cnt,ans;int val[65],num[65];inline void dfs(int now,int left){if (left==0){int ret=0;int bot=1;for (int i=1;i<=cnt;i++){ret+=num[i]*(num[i]-1)/2*val[i]+val[i]/2*num[i];for (int j=i+1;j<=cnt;j++)ret+=num[i]*num[j]*Gcd(val[i],val[j]);}for (int i=1;i<=cnt;i++)(bot*=Pow(val[i],num[i])*fac[num[i]]%P)%=P;(bot=Pow(bot,P-2)*fac[n])%=P;(ans+=Pow(2,ret)*bot)%=P;return;}if (now>left) return;dfs(now+1,left);for (int i=1;i*now<=left;i++){val[++cnt]=now; num[cnt]=i;dfs(now+1,left-now*i);cnt--;}}int main(){freopen("t.in","r",stdin);freopen("t.out","w",stdout);Pre();//for (int i=1;i<=60;i++)//{ans=0;scanf("%d",&n);//n=i;dfs(1,n);(ans*=inv[n])%=P;printf("%d\n",ans);//}return 0;}

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