Random numbers and further usage

Question

I am designing random excercise sheets for my students. I'm able to get random numbers without repetition using the code from Random number without repetition in an \includegraphics. Now I want to use the random numbers to create unique tables. Eg. I have 20 possible mc questions and I want to use 5 different questions for each student. Each question is outsourced in a .tex file.

Example:

• random number 1 -> \input{1.tex}
• random number 3 -> \input{3.tex}
• random number 8 -> \input{8.tex}

Each X.tex file contains a table row like

a & b & c & d \\

Now my problem is the following error code if I use the tabular environment. I don't understand where the missing } is.

! Extra }, or forgotten \endgroup. <template> \unskip \hfil } \hskip \tabcolsep \endtemplate l.56 \randomincludegraphics{total}?

Here is my MWE:

\documentclass[a4paper,12pt]{article}
\usepackage{tikz}
\begin{document}
\makeatletter
\def\declarenumlist#1#2#3{%
  @ifundefined{c@#1@listcount}{\newcounter{#1@listcount}}{}%
  \setcounter{#1@listcount}{1}%
  \begingroup
  \count@=#2\relax
  \def\x{}%
  \loop
  \edef\x{\x{\the\count@}}%
  \global\expandafter\let\csname#1@\number\count@ @used\endcsname\relax
  \ifnum\count@<#3\relax
    \advance\count@@ne
    \stepcounter{#1@listcount}%
  \repeat
  \edef\x{\endgroup
    \noexpand\pgfmathdeclarerandomlist{#1}{\x}%
  }\x
  \expandafter\mathchardef\csname #1@number\endcsname\value{#1@listcount}%
  \setcounter{#1@listcount}{0}%
}
\newcommand{\pgfmathuniquerandomitem}[2]{%
  \pgfmathrandomitem#1{#2}%
  \ifnum\value{#2@listcount}=@nameuse{#2@number}%
    @latex@warning{List #2 exhausted}%
  \else
    @ifundefined{#2@#1@used}%
      {\stepcounter{#2@listcount}\global@namedef{#2@#1@used}{used}}%
      {\pgfmathuniquerandomitem#1{#2}}%
  \fi
}
\makeatother
\newcommand{\randomincludegraphics}[2][]{%
  \begingroup
  \pgfmathuniquerandomitem\z{#2}%
% Uncomment the following line for the production version
  \input{\z.tex}
% and remove the following line
%  I want to include \texttt{\z.pdf} with options ``\texttt{#1}''
  \endgroup
}
%I want 2 numbers because I have 2 possible rows
\begin{tabular}{cccc}
\declarenumlist{total}{1}{2}
\randomincludegraphics{total}
\randomincludegraphics{total}
\end{tabular}
%content of 1.tex
% a & b & c & d \
% content of 2.tex
% e & f & g & h \
\end{document}