How to add index outside a table in latex

Question

How to add index outside a table like this?

Thanks!

Answer 1

Going out on a limb here, I assume you want to create the indeces in the smaller font size...
I extended the table and reduzed the font size for the indeces. Using the array package for the rest.

Minimal working the solution:

\documentclass{article}
\usepackage{array}

\begin{document}

\begin{table}
\centering
\begin{tabular}{ccccc}
                & {\scriptsize 1}          & {\scriptsize 2}       & {\scriptsize 3}         & {\scriptsize 4}         \\ \cline{2-5}
{\scriptsize 1} &  \multicolumn{1}{|c|}{0} &\multicolumn{1}{|c|}{ }& \multicolumn{1}{|c|}{-2}& \multicolumn{1}{|c|}{ } \\ \cline{2-5}
{\scriptsize 2} &  \multicolumn{1}{|c|}{ } &\multicolumn{1}{|c|}{0}& \multicolumn{1}{|c|}{ } & \multicolumn{1}{|c|}{ } \\ \cline{2-5}
{\scriptsize 3} &  \multicolumn{1}{|c|}{ } &\multicolumn{1}{|c|}{ }& \multicolumn{1}{|c|}{0} & \multicolumn{1}{|c|}{ } \\ \cline{2-5}
{\scriptsize 4} &  \multicolumn{1}{|c|}{ } &\multicolumn{1}{|c|}{ }& \multicolumn{1}{|c|}{ } & \multicolumn{1}{|c|}{0} \\ \cline{2-5}
\end{tabular}
\end{table}

\end{document}

With the following result:

You can choose a different font size for the indices, like \small, \footnotesize or \tiny.