0是什么操作

var
 dis,s,t,w,v,next,list,p:array[0..500001]of longint;
 i,j,n,m,z,r,head,tail,ans,max,q:longint;
begin
 read(n,m,z);
 for i:=1 to m do
   begin
     read(s[i],t[i],w[i]);
     next[i]:=list[s[i]];
     list[s[i]]:=i;
   end;
 for i:=1 to n do
  dis[i]:=maxlongint div 2;
 tail:=1;
 p[1]:=z;
 dis[q]:=0;
 v[z]:=1;
 dis[1]:=0;
 i:=1;
  while head<tail do
    begin
      inc(head);
      i:=list[p[head]];
      while i>0 do
        begin
          if dis[s[i]]+w[i]<dis[t[i]] then
            begin
              dis[t[i]]:=dis[i]+w[i];
              if v[t[i]]=0 then
                begin
                  inc(tail);
                  v[t[i]]:=1;
                  p[tail]:=t[i];
                end;
             end;
          i:=next[i];
        end;
      v[list[head]]:=0;
    end;
 for i:=1 to n do write(dis[i],' ');
end.