[字典树 最小树形图] Codeforces Gym 100307 NEERC 13 D. Dictionary

先把所有串建成字典树 字典树上的边 边权为1
然后如果两个点 一个是另一个的后缀 那么就另一个向那一个连0的边
跑一通最小树形图就好了
我不会 拷了个板子
输出方案就很蛋疼了

#include<cstdio>#include<cstdlib>#include<algorithm>#include<cstring>using namespace std;inline char nc(){  static char buf[100000],*p1=buf,*p2=buf;  return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;}inline int read(char *s){  char c=nc(); int len=0;  for (;!(c>='a' && c<='z');c=nc());  for (;c>='a' && c<='z';s[++len]=c,c=nc()); s[++len]=0; return len-1;}const int INF=0x3f3f3f3f;  const int maxn=1000005;  int m;  struct Edge  {    int u,v,cost,id,ru,rv,rcost;  }edge[maxn];  int _u[maxn],_v[maxn];void add_Edge(int id,int u,int v,int c)  {      edge[id].id=id;      edge[id].u=edge[id].ru=u;      edge[id].v=edge[id].rv=v;      edge[id].cost=edge[id].rcost=c;    _u[id]=u; _v[id]=v;}  int pre[maxn],id[maxn],vis[maxn],in[maxn];  //// !!!!  int preid[maxn],useE[maxn];  int eA[maxn],eD[maxn];  int ex;  int zhuliu(int root,int n,int m)  {      int ex=m,res=0;      while(true)      {          for(int i=0;i<n;i++) in[i]=INF;          for(int i=0;i<m;i++)          {              if(edge[i].u!=edge[i].v&&edge[i].cost<in[edge[i].v])              {                  pre[edge[i].v]=edge[i].u;                  in[edge[i].v]=edge[i].cost;                  //// !!!!                  preid[edge[i].v]=edge[i].id;              }          }          for(int i=0;i<n;i++)              if(i!=root&&in[i]==INF) return -1;          int tn=0;          memset(id,-1,sizeof(id));          memset(vis,-1,sizeof(vis));          in[root]=0;          for(int i=0;i<n;i++)          {              res+=in[i];              int v=i;              //// !!!!              if(i!=root) useE[preid[i]]++;              while(vis[v]!=i&&id[v]==-1&&v!=root)              {                  vis[v]=i; v=pre[v];              }              if(v!=root&&id[v]==-1)              {                  for(int u=pre[v];u!=v;u=pre[u]) id[u]=tn;                  id[v]=tn++;              }          }          if(tn==0) break;          for(int i=0;i<n;i++)              if(id[i]==-1) id[i]=tn++;          for(int i=0;i<m;i++)          {              int v=edge[i].v;              edge[i].u=id[edge[i].u];              edge[i].v=id[edge[i].v];              if(edge[i].u!=edge[i].v)              {                  edge[i].cost-=in[v];                  //// !!!!                  eA[ex]=edge[i].id;                  eD[ex]=preid[v];                  edge[i].id=ex;                  ex++;              }          }          n=tn;          root=id[root];      }      //// !!!!      for(int i=ex-1;i>=m;i--)      {          if(useE[i])          {              useE[eA[i]]++; useE[eD[i]]--;          }      }      return res;  }  const int N=55;int n;char s[N][15]; int len[N];const int M=5005;int ncnt=1;int fat[M]; char c[M];int ch[M][26];inline void Ins(char *s,int n){  int p=1;  for (int i=1;i<=n;i++){    if (!ch[p][s[i]-'a']) ch[p][s[i]-'a']=++ncnt,fat[ncnt]=p,c[ncnt]=s[i];    p=ch[p][s[i]-'a'];  }}inline string Str(int p){  string s;  while (p!=1)    s=c[p]+s,p=fat[p];  return s;}inline bool Jud(string a,string b){  if (b.length()>a.length()) return 0;  int s=a.length()-b.length();  for (int i=0;i<b.length();i++)    if (a[s+i]!=b[i])      return 0;  return 1;}int Pre[M];int _fat[M];inline int Fat(int u){  return u==_fat[u]?u:_fat[u]=Fat(_fat[u]);}int w[M][M];int idx[M];int main(){  freopen("dictionary.in","r",stdin);  freopen("dictionary.out","w",stdout);  scanf("%d",&n);  ncnt=1;  for (int i=1;i<=n;i++)    len[i]=read(s[i]),Ins(s[i],len[i]);  for (int i=0;i<ncnt;i++)    for (int j=0;j<ncnt;j++)      w[i][j]=1<<30;  for (int i=2;i<=ncnt;i++)    add_Edge(m++,fat[i]-1,i-1,2),w[fat[i]-1][i-1]=1;  for (int i=2;i<=ncnt;i++)    for (int j=2;j<=ncnt;j++)      if (i!=j && Jud(Str(i),Str(j)))    add_Edge(m++,i-1,j-1,1),w[i-1][j-1]=0;  int ans=zhuliu(0,ncnt,m)+1;  for (int i=0;i<m;i++)      if (useE[i]&&edge[i].rcost)        Pre[_v[i]+1]=_u[i]+1;  for (int i=1;i<=ncnt;i++) _fat[i]=i;  for (int i=2;i<=ncnt;i++)    if (w[Pre[i]-1][i-1]==0)      _fat[Fat(i)]=Pre[i];  int tot=0;  for (int i=1;i<=ncnt;i++) if (Fat(i)==i) idx[i]=++tot;  printf("%d\n",tot);  printf("0\n");  for (int i=2;i<=ncnt;i++)    if (Fat(i)==i)      printf("%d %c\n",idx[Fat(fat[i])],c[i]);  return 0;}