old/PAS/Gray codes.pas

const
 table : array [0..3] of string[2] = ('00','01','11','10');
var
 i,j,k,ni,nj,nk,num : shortint;
 S					: Text;

begin
  ni:=1;nj:=1;nk:=1;
  i:=0;j:=0;k:=0;num:=0;
  Assign(S,'out');
  Rewrite(S);

  while i <> (3*(ni+1) div 2+ni) do
   begin
    while j <> (3*(nj+1) div 2+nj) do
     begin
      while k <> (3*(nk+1) div 2+nk) do
       begin
        WriteLn(S,table[i],table[j],table[k],'  -  ',num);
        inc(num);
        inc(k,nk);
       end;
      dec(k,nk);
      inc(j,nj);
      nk:=-nk;
     end;
     dec(j,nj);
     inc(i,ni);
     nj:=-nj;
   end;
  close(S);
end.