Toki Learning 2D: Stack dan Queue

program latihan2d_1;

var
	a : array[0..99999] of longint;
	i,n : longint;
	kript : integer;
	h,t : longint;
	angka : longint;

procedure baca(var kript : integer);

var
	idx : integer;
	huruf : char;
	kata : string;
	kamus : array[0..3] of string = ('push_front','push_back','pop_front','pop_back');

begin
	idx := 0;
	kata := '';
	read(huruf);
	while (huruf <> ' ') and (huruf <> char(26)) and (huruf <> char(10)) and (huruf <> char(13)) do begin
		kata := kata + huruf;
		read(huruf);
	end;

	while (idx <= 3) and (kript <> idx) do begin
		if kata = kamus[idx] then begin
			kript := idx;
		end;
	//	writeln('menunggu');
		inc(idx);
	//	writeln(idx,' ',kata);
	end;
//	writeln('selesai');
//	writeln(kript);
end;

procedure push_front(var angka, h,t : longint);

begin
	if h = -1 then begin h := 0; t := 0; end else begin
	if h = 99999 then begin h := 0; end else begin
		h := h + 1;
	end;
	end;
	a[h] := angka;
//	writeln('h = ',h,' ',angka);
end;

procedure push_back(var angka,h,t : longint);

begin
//	writeln(t,' kedua');
	if t = -1 then begin h := 0; t := 0; end else begin
	if t = 0 then begin t := 99999;  end else begin
		t := t - 1;
	end;
	end;
	a[t] := angka;
//	writeln('t = ',t,' ',angka);
end;

procedure pop_front(var h,t : longint);

begin
	if h <> -1 then begin
		if h = 0 then begin h := 99999 end else begin
			h := h - 1;
		end;
	end;
//	writeln('h = ',h,' ',angka);
end;

procedure pop_back(var h,t : longint);

begin
	if t <> -1 then begin
		if t = 99999 then begin t := 0; end else begin
			t := t + 1;
		end;
	end;
//	writeln('t = ',t,' ',angka);
end;

procedure kirim(a : array of longint; h,t : longint);

var
	u : longint;

begin
	if t > h then begin
		for u := h downto 0 do begin
			writeln(a[u]);
		end;
		for u := 99999 downto t do begin
			writeln(a[u]);
		end;
	end else begin
		for u := h downto t do begin
			writeln(a[u]);
		end;
	end;
end;

begin
		readln(n);
		h := -1;
		t := -1;
		for i := 0 to 99999 do begin
			a[i] := 0;
		end;
		for i := 1 to n do begin
			kript := -1;
			baca(kript);
			case kript of
				0: begin readln(angka); push_front(angka,h,t);
				end;
				1: begin readln(angka); push_back(angka,h,t); end;
				2: begin readln; pop_front(h,t); end;
				3: begin readln; pop_back(h,t); end;
			end;
		//	writeln(h,' ',t);
		end;

		kirim(a,h,t);
end.