bzoj2938

显然AC自动机，但什么叫无限生成呢？
显然就是在AC自动机上匹配，出现了一个环（不能走结尾节点）
直接搜索即可

 var trie:array[..,''..''] of longint;
     q,f:array[..] of longint;
     can,v,r:array[..] of boolean;
     l,n,i,t,j,k:longint;
     s:ansistring;

 procedure ac;
   var j,x,y,h,r:longint;
       c:char;
   begin
     h:=;
     r:=;
     for c:='' to '' do
       if trie[,c]<> then
       begin
         inc(r);
         q[r]:=trie[,c];
       end;
     while h<=r do
     begin
       x:=q[h];
       for c:='' to '' do
         if trie[x,c]<> then
         begin
           y:=trie[x,c];
           inc(r);
           q[r]:=y;
           j:=f[x];
           while (j>) and (trie[j,c]=) do j:=f[j];
           f[y]:=trie[j,c];
           if can[trie[j,c]] then can[y]:=true;
         end;
       inc(h);
     end;
   end;

 function dfs(x:longint):boolean;
   var c:char;
       j:longint;
   begin
     if can[x] then exit(false);
     if v[x] then exit(true)
     else v[x]:=true;
     for c:='' to '' do
     begin
       j:=x;
       while (j>) and (trie[j,c]=) do j:=f[j];
       if r[trie[j,c]] then continue;
       if dfs(trie[j,c]) then exit(true);
     end;
     v[x]:=false;
     r[x]:=true;
     exit(false);
   end;

 begin
   readln(n);
   t:=;
   for i:= to n do
   begin
     readln(s);
     l:=length(s);
     j:=;
     for k:= to l do
     begin
       if trie[j,s[k]]= then
       begin
         inc(t);
         trie[j,s[k]]:=t;
       end;
       j:=trie[j,s[k]];
     end;
     can[j]:=true;
   end;
   ac;
   if dfs() then writeln('TAK') else writeln('NIE');
 end.