P1631: [Usaco2007 Feb]Cow Party

还是水题，接近于裸的spfa（个人比较喜欢用spfa，dijkstra不太喜欢用），代码附上

 const maxn=;
 type
   link=^node;
   node=record
     t,d:longint;
     f:link;
   end;
 var n,m,s,i,j,u,v,w,max:longint;
 adj:array[..] of link;
 f:array[..] of longint;
 d,val:array[..] of longint;
 went:array[..] of boolean;
 procedure insert(f,t,d:longint);
 var p:link;
 begin
   new(p);
   p^.f:=adj[f];
   p^.t:=t;
   p^.d:=d;
   adj[f]:=p;
 end;
 procedure spfa(s:longint);
 var l,r,now,i:longint;
 p:link;
 begin
   for i:= to n do
     d[i]:=maxn;
   fillchar(went,sizeof(went),true);
   l:=; r:=; f[]:=s; d[s]:=; went[s]:=false;
   while l<=r do
     begin
       now:=f[l];
       p:=adj[now];
       while p<>nil do
         begin
           if d[p^.t]>d[now]+p^.d then
             begin
               d[p^.t]:=d[now]+p^.d;
               if went[p^.t] then
                 begin
                   went[p^.t]:=false;
                   inc(r);
                   f[r]:=p^.t;
                 end;
             end;
           p:=p^.f;
         end;
       went[now]:=true;
       inc(l);
     end;
 end;
 begin
   readln(n,m,s);
   for i:= to m do
     begin
       readln(u,v,w);
       insert(u,v,w);
       //insert(v,u,w);
     end;
   for i:= to n do
     begin
       spfa(i);
       val[i]:=d[s];
       //writeln(sb);
       //writeln(d[s]);
     end;
   spfa(s);
   for i:= to n do
     //if i<>s then
       begin
         inc(val[i],d[i]);
         if val[i]>max then max:=val[i];
       end;
   writeln(max);
 end.

(转载请注明出处：http://www.cnblogs.com/Kalenda/)