TYVJ1704 Poj3249 绿豆蛙寻宝

　 　 题目说是拓扑图，所以提示是DP，之前跟FK学到逆拓扑这次用了。需要注意的是题目要求一条完整的路，所以初始化为-oo。因为TUOPU写萎了，WA了2次。之前FK那个题因为是无向图，而且是树，而且起点还是root，所以可以直接BFS就得到拓扑序，这个题不行。

uses math;
const maxn=100000;
      maxm=11000000;
var a,Q,Adjlist,d:array[1..maxn] of longint;
    f:array[1..maxn] of int64;
    vis:array[1..maxn] of boolean;
    v,next:array[1..maxm] of longint;
    count,x,y,i,h,t,tot,n,m:longint;
    ans:int64;
procedure build(x,y:longint);
          begin
          inc(tot);
          v[tot]:=y;
          next[tot]:=Adjlist[x];
          Adjlist[x]:=tot;
          end;
procedure TUOPUSort;
          var i:longint;
          begin
          while h<t do begin
            inc(h);i:=Adjlist[Q[h]];
            while i<>0 do begin
              dec(d[v[i]]);
              if(not vis[v[i]])and(d[v[i]]=0)
                then begin
                     inc(t);Q[t]:=v[i];
                     vis[v[i]]:=true;
                     end;
              i:=next[i];end;end;
          end;
procedure calc;
          var i,u:longint;
          begin
          for h:=t downto 1 do
            begin
            i:=Adjlist[Q[h]];
            if i=0 then f[Q[h]]:=A[Q[h]]
                   else f[Q[h]]:=$8fffffffffffffff;
            while i<>0 do begin
              f[Q[h]]:=max(f[v[i]]+A[Q[h]],f[Q[h]]);
              i:=next[i];end;
            end;
          end;
begin
readln(n,m);ans:=$8fffffffffffffff;h:=0;t:=0;
for i:=1 to n do readln(a[i]);
for i:=1 to m do
  begin
  readln(x,y);
  build(x,y);
  inc(d[y]);
  end;
for i:=1 to n do
  if(d[i]=0)
    then begin
         inc(t);
         Q[t]:=i;
         vis[i]:=true;
         end;
count:=t;
TUOPUSort;calc;
for i:=1 to count do
  ans:=max(f[Q[i]],ans);
writeln(ans);
end.