• [AGC005]:F


    F - Many Easy Problems


    Time limit : 5sec / Memory limit : 512MB

    Score : 1900 points

    Problem Statement

    One day, Takahashi was given the following problem from Aoki:

    • You are given a tree with N vertices and an integer K. The vertices are numbered 1 through N. The edges are represented by pairs of integers (ai,bi).
    • For a set S of vertices in the tree, let f(S) be the minimum number of the vertices in a subtree of the given tree that contains all vertices in S.
    • There are ways to choose K vertices from the trees. For each of them, let S be the set of the chosen vertices, and find the sum of f(S) over all ways.
    • Since the answer may be extremely large, print it modulo 924844033(prime).

    Since it was too easy for him, he decided to solve this problem for all K=1,2,…,N.

    Constraints

    • 2≦N≦200,000
    • 1≦ai,biN
    • The given graph is a tree.

    Input

    The input is given from Standard Input in the following format:

    N
    a1 b1
    a2 b2
    :
    aN1 bN1
    

    Output

    Print N lines. The i-th line should contain the answer to the problem where K=i, modulo 924844033.

    大意:从一棵树中选择$k$个点,记$f(S)$为最小的包括点集$S$的联通子图,求每个$k$的$sum F(S)$。

    思路{

      直接做比较麻烦。考虑计算点的贡献。

      一个点$u$被算入联通子图当且仅当选出的$k$个点没有全部在它的子树内或者是子树外。

      那么用总数减去不合法方案数贡献就是$C_n^k-sum_{i=1}^{k}C_{a_i}^k$

      (其中$a_i$为删除$u$后各个连通块的大小。

      对于$k$来说把这些项单独提出来,在每一个组合数的前面都会有一个系数$p_i$
      则$Ans_k=sum_{i=k}^np_i*C_i^k=dfrac{1}{k!}*sum_{i=k}^{n}dfrac{p_i*i!}{(i-k)!}$

      把记录$p_i*i!$的数组设为$A$,记录$dfrac{1}{(i-k)!}$数组翻转设为$B$;

      不难发现变成了一个卷积的形式,由于还要取模,直接上$NTT$做多项式乘法就好了。

    }

    #include<bits/stdc++.h>
    #define LL long long
    #define RG register
    #define il inline
    #define N 400010
    #define mod 924844033
    using namespace std;
    struct ed{int nxt,to;}e[N*2];
    int head[N],tot,n,m,R[N*2],A[N*2],B[N*2],fac[N*2],_fac[N*2],sz[N];
    void link(int u,int v){e[tot].nxt=head[u];e[tot].to=v;head[u]=tot++;}
    void lnk(int u,int v){link(u,v),link(v,u);}
    void dfs(int u,int faa){
      A[n]++;
      sz[u]=1;
      for(int i=head[u];i!=-1;i=e[i].nxt){
        int v=e[i].to;if(v==faa)continue;
        dfs(v,u);sz[u]+=sz[v];
        A[sz[v]]--;if(A[sz[v]]<0)A[sz[v]]+=mod;
      }
      A[n-sz[u]]--;if(A[n-sz[u]]<0)A[n-sz[u]]+=mod;  
    }
    int qp(int a,int b){
      if(!b)return 1;if(a==1)return a;
      int temp=qp(a,(b>>1));
      temp=1ll*temp*temp%mod;
      if(b&1)temp=1ll*temp*a%mod;
      return temp;
    }
    void NTT(int *a,int f){
      for(int i=0;i<n;++i)if(i<R[i])swap(a[i],a[R[i]]);
      for(int i=1;i<n;i<<=1){
        int gn=qp(5,(mod-1)/(i<<1));
        for(int j=0;j<n;j+=(i<<1)){
          int g=1;
          for(int k=0;k<i;++k,g=1ll*g*gn%mod){
    	int x=a[j+k],y=1ll*g*a[j+k+i]%mod;
    	a[j+k]=(x+y)%mod;
    	a[j+k+i]=(x-y+mod)%mod;
          }
        }
      }
      if(f==-1){
        reverse(a+1,a+n);
        int _n=qp(n,mod-2);
        for(int i=0;i<n;++i)a[i]=1ll*a[i]*_n%mod;
      }
    }
    int main(){
      memset(head,-1,sizeof(head));
      scanf("%d",&n);for(int i=1;i<n;++i){int u,v;scanf("%d%d",&u,&v),lnk(u,v);}
      dfs(1,1);
      fac[1]=1;fac[0]=1;
      for(int i=2;i<=n;++i)fac[i]=1ll*fac[i-1]*i%mod,A[i]=1ll*A[i]*fac[i]%mod;
      _fac[n]=qp(fac[n],mod-2);for(int i=n;i;--i)_fac[i-1]=1ll*_fac[i]*i%mod;
      for(int i=1;i<=n;++i)B[i]=_fac[n-i];
      m=n;int L=0;
      for(n=1;n<=(m<<1);n<<=1)L++;
      for(int i=0;i<n;++i)R[i]=(R[i>>1]>>1)|((i&1)<<(L-1));
      NTT(A,1),NTT(B,1);
      for(int i=0;i<n;++i)A[i]=1ll*A[i]*B[i]%mod;
      NTT(A,-1);
      for(int i=1;i<=m;++i)printf("%d
    ",1ll*A[m+i]*_fac[i]%mod);
      return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/zzmmm/p/7784846.html
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