Re-creating Tikz image with other package

Question

I have an array in my latex template something like this:

This picture is made with Tikz. Here is the code:

\begin{figure}[!h]
\centering
\begin{tikzpicture} [
                        nodes in empty cells,
                        nodes={minimum size=10mm},
                        row sep=-\pgflinewidth,
                        column sep=-\pgflinewidth
                    ]
    border/.style={draw}
\tikzstyle{bg_gray} = [fill=gray!20]

\matrix(vector)[
    matrix of nodes,
    row 1/.style={nodes={draw,font=\strut}},
    row 2/.style={nodes={draw=none, minimum width=0.4cm}},
    nodes={draw}
    ]
{
    |[draw=none, minimum width=1.5cm]| $\textbf{a[i]}$ & $4$ & $7$ & $10$ & |[bg_gray]| $6$ & |[bg_gray]| $4$ & |[bg_gray]| $1$ & $3$ & $6$ & $11$ & |[bg_gray]| $9$ & |[bg_gray]| $5$ \\
    \textbf{\small{i}} & \small{0} & \small{1} & \small{2} & \small{3} & \small{4} & \small{5} & \small{6} & \small{7} & \small{8} & \small{9} & \small{10} \\
};


\end{tikzpicture}
\caption{A random array for observation}
\label{fig:array_observation}
\end{figure}

But my problem is some system like ACM doesn't allow to use Tikz (List of Accepted LaTeX Packages). Please suggest how I can re-create a similar image using any of other packages they allowed?

Answer 1

The following uses only approved packages:

\documentclass{article}
\usepackage[table]{xcolor}
\usepackage{array}
\begin{document}
\begin{figure}
  \centering
  \makebox[25pt]{$\mathbf{Arr}[\mathbf{i}]$}
  \begin{tabular}{ | *{11}{w{c}{12pt} |} }
    \hline
      \rule[-.75\normalbaselineskip]{0pt}{2\normalbaselineskip}% Strut
      16 & 5 & 11 & 
      \cellcolor{gray!20}6 & \cellcolor{gray!20}7 & \cellcolor{gray!20}3 &
      8 & 6 & 15 &
      \cellcolor{gray!20}21 & \cellcolor{gray!20}14 \
    \hline
  \end{tabular}
\medskip
\footnotesize
  \makebox[25pt]{$\mathbf{i}$}
  \begin{tabular}{ *{11}{w{c}{\dimexpr12pt+\arrayrulewidth}} }
      0 &  1 & 2 &
      3 &  4 & 5 &
      6 &  7 & 8 &
      9 & 10
  \end{tabular}
  \caption{An array $\mathbf{Arr}$}
\end{figure}
\end{document}