bzoj 4754: [Jsoi2016]独特的树叶

不得不说这是神题。

%%%   http://blog.csdn.net/samjia2000/article/details/51762811

 #include <cstdio>
 #include <iostream>
 #include <cstring>
 #include <algorithm>
 #include <set>
 #define inf 0x3f3f3f3f
 #define LL long long
 #define eps 1e-8
 #define N 100005
 using namespace std;
 inline int ra()
 {
     int x=,f=; char ch=getchar();
     while (ch<'' || ch>'') {if (ch=='-') f=-; ch=getchar();}
     while (ch>='' && ch<='') {x=x*+ch-''; ch=getchar();}
     return x*f;
 }

 const int mod=1e++;
 const int prime=;

 LL tim[N],q[N];
 int k;
 struct node{int to,x; LL v;}u[N];
 bool cmp(node a, node b){return a.v<b.v;}

 struct tree
 {
     int cnt,head[N];
     struct edge{int to,next;}e[N<<];
     int n,r[N],fa[N],size[N];
     LL v[N],rt[N],f[N];
     LL suf[N],pre[N];

     void insert(int x, int y){e[++cnt].next=head[x]; e[cnt].to=y; head[x]=cnt;}
     void init()
     {
         cnt=;
         for (int i=; i<=n; i++) head[i]=r[i]=f[i]=fa[i]=rt[i]=;
         for (int i=; i<n; i++)
         {
             int x=ra(),y=ra();
             insert(x,y); insert(y,x);
             r[x]++; r[y]++;
         }
     }

     void dfs1(int x)
     {
         size[x]=;
         for (int i=head[x];i;i=e[i].next)
         {
             if (e[i].to==fa[x]) continue;
             fa[e[i].to]=x;
             dfs1(e[i].to);
             size[x]+=size[e[i].to];
         }
         k=;
         for (int i=head[x];i;i=e[i].next)
             if (fa[e[i].to]==x) q[++k]=v[e[i].to];
         sort(q+,q+k+);
         v[x]=;
         for (int i=; i<=k; i++) v[x]=(v[x]*prime%mod+q[i])%mod;
         v[x]=(v[x]*prime%mod+size[x])%mod;
     }

     void dfs2(int x)
     {
         k=;
         if (x>) u[++k].v=f[x],u[k].to=fa[x];
         for (int i=head[x];i;i=e[i].next)
             if (fa[e[i].to]==x)
             {
                 u[++k].to=e[i].to;
                 u[k].v=v[e[i].to];
             }
         sort(u+,u++k,cmp);
         for (int i=; i<=k; i++) pre[i]=(pre[i-]*prime%mod+u[i].v)%mod;
         suf[k+]=;
         for (int i=k; i>=; i--) suf[i]=(suf[i+]+u[i].v*tim[k-i]%mod)%mod;
         for (int i=; i<=k; i++)
             if (u[i].to!=fa[x])
             {
                 f[u[i].to]=(pre[i-]*tim[k-i]%mod+suf[i+])%mod;
                 f[u[i].to]=(f[u[i].to]*prime%mod+n-size[u[i].to])%mod;
             }
         for (int i=head[x];i;i=e[i].next)
             if (fa[e[i].to]==x) dfs2(e[i].to);
     }
     void cal()
     {
         dfs1(); dfs2();
         for (int x=; x<=n; x++)
         {
             k=;
             for (int i=head[x];i;i=e[i].next)
                 if (fa[e[i].to]==x) q[++k]=v[e[i].to];
             if (fa[x]) q[++k]=f[x];
             sort(q+,q+k+);
             rt[x]=;
             for (int i=; i<=k; i++) rt[x]=(rt[x]*prime%mod+q[i])%mod;
             rt[x]=(rt[x]*prime%mod+n)%mod;
         }
     }
 }a,b;

 int m;
 set<LL> s;

 int main(int argc, char const *argv[])
 {
     tim[]=; s.clear();
     m=ra();
     for (int i=; i<=m+; i++) tim[i]=tim[i-]*prime%mod;
     a.n=m; a.init(); b.n=m+; b.init(); a.cal(); b.cal();
     for (int i=; i<=m; i++) s.insert(a.rt[i]);
     for (int i=; i<=m+; i++)
         if (b.r[i]== && ((i!= && s.find(b.f[i])!=s.end()) || (i== && s.find(b.v[b.e[b.head[i]].to])!=s.end())))
         {
             printf("%d\n",i); return ;
         }
     return ;
 }