P1179: [Apio2009]Atm

缩点+spfa最短路，因为最终不可能有环，所以直接spfa。

 const maxe=;
 type
   node=record
     f,t:longint;
   end;
 var n,m,s,i,j,ans,cnt,num,u,x,dgr:longint;
 h,he,dfn,low,q,d,v,va,bl:array[..maxe] of longint;
 b,bi:array[..maxe] of node;
 f:array[..maxe*] of longint;
 p:array[..maxe] of boolean;
 function min(a,b:longint):longint;
 begin
   if a>b then exit(b) else exit(a);
 end;
 procedure insert(u,v:longint);
 begin
   with bi[i] do
     begin
       f:=he[u];
       t:=v;
     end;
   he[u]:=i;
 end;
 procedure reinsert(u,v:longint);
 begin
   inc(cnt);
   with b[cnt] do
     begin
       f:=h[u];
       t:=v;
     end;
   h[u]:=cnt;
 end;
 procedure readd;
 var i,e,v:longint;
 begin
   cnt:=;
   for i:= to n do
     begin
       e:=he[i];
       while e<> do
         begin
           v:=bi[e].t;
           if bl[i]<>bl[v] then reinsert(bl[i],bl[v]);
           e:=bi[e].f;
         end;
     end;
 end;
 procedure tarjan(x:longint);
 var e,t,j:longint;
 begin
   inc(dgr); inc(num);
   p[x]:=true; f[num]:=x; dfn[x]:=dgr; low[x]:=dgr;
   e:=he[x];
   while e<> do
     begin
       t:=bi[e].t;
       if dfn[t]= then
         begin
           tarjan(t);
           if low[x]>low[t] then low[x]:=low[t];
         end
       else if (p[t]) and (dfn[t]<low[x]) then low[x]:=dfn[t];
       e:=bi[e].f;
     end;
   if dfn[x]=low[x] then
     begin
       j:=; inc(cnt);
       while j<>x do
         begin
           j:=f[num];
           dec(num);
           p[j]:=false;
           bl[j]:=cnt;
           //writeln(j,'   ',cnt);
           inc(v[cnt],va[j]);
         end;
     end;
 end;
 procedure spfa;
 var e,t,now,l,r:longint;
 begin
   fillchar(p,sizeof(p),true);
   fillchar(d,sizeof(d),);
   l:=; r:=; f[]:=bl[s]; p[bl[s]]:=false; d[bl[s]]:=v[bl[s]]; //writeln(v[bl[s]]);
   while l<=r do
     begin
       now:=f[l];
       e:=h[now];
       while e<> do
         begin
           t:=b[e].t;
           //if t=1 then writeln('x',now,' ',v[t]);
           if d[t]<d[now]+v[t] then
             begin
               d[t]:=d[now]+v[t];
               if p[t] then
                 begin
                   p[t]:=false;
                   inc(r);
                   f[r]:=t;
                 end;
             end;
           e:=b[e].f;
         end;
       inc(l);
       p[now]:=true;
     end;
 end;
 begin
   readln(n,m);
   for i:= to m do
     begin
       readln(u,x);
       insert(u,x);
     end;
   for i:= to n do readln(va[i]);
   fillchar(p,sizeof(p),false);
   for i:= to n do if dfn[i]= then tarjan(i);
   readln(s,m);
   readd;
   //for i:=1 to 4 do writeln(v[i]);
   spfa;
   for i:= to m do
     begin
       read(u);
       if d[bl[u]]>ans then ans:=d[bl[u]];
     end;
   writeln(ans);
 end.

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