NKONEARC - Mạng máy tính

Tác giả: RR

Ngôn ngữ: Pascal

const
  FINP='';
  FOUT='';
var
  f1,f2:text;
  vao,ra:array [1..2000] of byte;
  n,m:longint;
procedure openF;
begin
  assign(f1,FINP); reset(f1);
  assign(f2,FOUT); rewrite(f2);
end;
procedure closeF;
begin
  close(f1); close(f2);
end;
procedure inp;
var
  i,x,y:longint;
begin
  readln(f1,n,m);
  for i:=1 to m do
    begin
      readln(f1,x,y);
      vao[y]:=1;
      ra[x]:=1;
    end;
end;
procedure ans;
var
  i,u,v,count:longint;
begin
  count:=0;
  for i:=1 to n do
    begin
      if vao[i]=0 then
        begin
          u:=i;
          inc(count);
        end
      else if ra[i]=0 then
        begin
          v:=i;
          inc(count);
        end;
      if count=2 then break;
    end;
  writeln(f2,'YES');
  write(f2,v,' ',u);
end;
begin
  openF;
  inp;
  ans;
  closeF;
end.

Download