bzoj2427

一开始读错题导致各种不会做，无奈
其实是一道水题，缩点反向建图树形dp即可

 type link=^point;
      point=record
        po:longint;
        next:link;
      end;

 var dfn,low,st,w,be,v,c:array[..] of longint;
     e:array[..] of link;
     fa,vis,f:array[..] of boolean;
     dp:array[..,..,..] of longint;
     y,s,h,t,ans,i,j,n,m,x:longint;
     ch:boolean;

 function min(a,b:longint):longint;
   begin
     if a>b then exit(b) else exit(a);
   end;

 function max(a,b:longint):longint;
   begin
     if a>b then exit(a) else exit(b);
   end;

 procedure add(x,y:longint);
   var p:link;
   begin
     new(p);
     p^.po:=y;
     p^.next:=e[x];
     e[x]:=p;
   end;

 procedure tarjan(x:longint);
   var y,r:longint;
       p:link;
   begin
     inc(h);
     dfn[x]:=h;
     low[x]:=h;
     vis[x]:=true;
     f[x]:=true;
     inc(t);
     st[t]:=x;
     p:=e[x];
     while p<>nil do
     begin
       y:=p^.po;
       if not vis[y] then
       begin
         tarjan(y);
         low[x]:=min(low[x],low[y]);
       end
       else if f[y] then low[x]:=min(low[x],low[y]);
       p:=p^.next;
     end;
     if dfn[x]=low[x] then
     begin
       while st[t+]<>x do
       begin
         r:=st[t];
         be[r]:=x;
         f[r]:=false;
         dec(t);
       end;
     end;
   end;

 procedure treedp(x:longint);
   var y,i,j,k:longint;
       p:link;
   begin
     p:=e[x];
     dp[x,w[x],]:=v[x];
     k:=;
     while p<>nil do
     begin
       y:=p^.po;
       treedp(y);
       k:=-k;
       for i:= to m do
         dp[x,i,k]:=dp[x,i,-k];
       for i:= to m-w[x] do
         if dp[y,i,]> then
         begin
           for j:=w[x] to m-i do
             dp[x,j+i,k]:=max(dp[x,j+i,k],dp[x,j,-k]+dp[y,i,]);
         end;
       p:=p^.next;
     end;
     if k= then
       for i:= to m do
          dp[x,i,]:=dp[x,i,];
   end;

 begin
   readln(n,m);
   for i:= to n do
     read(w[i]);
   for i:= to n do
     read(v[i]);
   for i:= to n do
   begin
     read(c[i]);
     if c[i]<> then add(i,c[i]);
   end;
   for i:= to n do
     if not vis[i] then
     begin
       h:=;
       t:=;
       tarjan(i);
     end;

   for i:= to n do
   begin
     if be[i]<>i then
     begin
       inc(w[be[i]],w[i]);
       inc(v[be[i]],v[i]);
     end;
     e[i]:=nil;
   end;
   for i:= to n do
     if be[i]=i then
     begin
       if (be[c[i]]=i) or (c[i]=) then add(,i)
       else add(be[c[i]],i);
     end;
   ans:=;
   v[]:=;
   w[]:=;
   treedp();
   for i:= to m do
     ans:=max(ans,dp[,i,]);
   writeln(ans);
 end.