TikZ matrix as a replacement for tabular

Question

I would like to use TikZ matrices to for some drawings. I am currently using nodes and positioning them manually to simulate a tabular. That helps in positioning arrows and shading.

However, if I use something like the following code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}

\begin{tikzpicture}
\matrix [matrix of nodes,row sep=0,column 2/.style={nodes={rectangle,draw,minimum width=3em}}]
{
0   & 6 \\
1   & 3 \\
};
\end{tikzpicture}
\end{document}

The nodes' lower and upper borders do not overlap, resulting in a double border between nodes.

edit: Jake suggested a very nice solution, using negative row separation row sep. That work very well for one column tables. But the columns are misaligned when there are more columns.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\usetikzlibrary{positioning}
\begin{document}

\begin{tikzpicture}[cell/.style={rectangle,draw=black},
space/.style={minimum height=1.5em,matrix of nodes,row sep=-\pgflinewidth,column sep=-\pgflinewidth,column 1/.style={font=\ttfamily}}]

\matrix (first) [space, column 1/.style={font=\ttfamily},column 2/.style={nodes={cell,minimum width=2em}}]
{
0   & 6 \\
1   & 3 \\
2   & 9 \\
};

\matrix (second) [right=of first, space, column 2/.style={minimum width=3em,nodes={cell,minimum width=3.5em}},column 3/.style={nodes={cell,minimum width=2em}}]
{
0   &a  & 6 \\
1   &   & 3 \\
2   &c  & 9 \\
};

\matrix [right=of second, space, column 2/.style={minimum width=3em,nodes={cell,minimum width=3.5em}},column 3/.style={nodes={cell,minimum width=2em}}]
{
0   &a  & 6 \\
1   &b  & 3 \\
2   &c  & 9 \\
};
\end{tikzpicture}
\end{document}

Answer 1

If you set row sep to -\pgflinewidth, the lines will overlap exactly:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}
\matrix [matrix of nodes,row sep=-\pgflinewidth,column 2/.style={nodes={rectangle,draw,minimum width=3em}}]
{
0   & 6 \\   1   & 3 \\   };
\end{tikzpicture}
\end{document}

In order to make sure that the cells align correctly horizontally, you need to make the text height and text depth the same across the entire row. By setting nodes in empty cells, all cells will be drawn, even if no content is provided. Alternatively, you can enter {} into empty cells to achieve the same effect.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix,positioning}
\begin{document}
\begin{tikzpicture}[cell/.style={rectangle,draw=black},
space/.style={minimum height=1.5em,matrix of nodes,row sep=-\pgflinewidth,column sep=-\pgflinewidth,column 1/.style={font=\ttfamily}},text depth=0.5ex,text height=2ex,nodes in empty cells]

\matrix (first) [space, column 1/.style={font=\ttfamily},column 2/.style={nodes={cell,minimum width=2em}}]
{
0   & 6 \\   1   & 3 \\   2   & 9 \\   };

\matrix (second) [right=of first, space, column 2/.style={minimum width=3em,nodes={cell,minimum width=3.5em}},column 3/.style={nodes={cell,minimum width=2em}}]
{
0   &a  & 6 \\   1   &   & 3 \\   2   &c  & 9 \\   };

\matrix [right=of second, space, column 2/.style={minimum width=3em,nodes={cell,minimum width=3.5em}},column 3/.style={nodes={cell,minimum width=2em}}]
{
0   &a  & 6 \\   1   &b  & 3 \\   2   &c  & 9 \\   };
\end{tikzpicture}
\end{document}

Answer 2

For information, the environment {NiceTabular} of nicematrix creates tabulars similar to {tabular} but with PGF/Tikz nodes under the cells, rows and columns. You can use those nodes with Tikz. However, you can also add rules in the tabular with the classical technics of {tabular} (eg: \hline).

In the following code, I have used the key hvlines which draws all the rules (excepted in the "first" column and "first" row).

\documentclass{article}
\usepackage{nicematrix,tikz}
\usetikzlibrary{arrows.meta}

\begin{document}

\renewcommand{\arraystretch}{1.5}

\begin{NiceTabular}{>{\ttfamily}rc}[name=Left]
M         & \Block[draw]{} 0 \\
\\
L         & \Block[draw]{} 4 \\
\\
available & \Block[draw]{} 8 \\
\end{NiceTabular}\hspace{3cm}
\begin{NiceTabular}
  [
    first-col,
    code-for-first-col=\inteval{\value{iRow}-1},
    first-row,
    hvlines,
    color-inside,
    name = Right
  ]
  {cc}  
& element & next \\
& \cellcolor{gray!30}
          & $6$  \\
& 1       & $3$  \\
& b       & $9$  \\
&         & $5$  \\
& \cellcolor{gray!30}
          & $7$  \\
&         & $-1$ \\
&         & $10$ \\
& a       & $2$  \\
&         & $11$ \\
& c       & $-1$ \\
& c       & $-1$ \\
&         & $1$  \\ 
\end{NiceTabular}

\begin{tikzpicture}[overlay,remember picture]
  \draw [->] (Left-1.5-|Left-last) to [bend right] (Right-1.5-|Right-1) ; 
  \draw [->] (Left-3.5-|Left-last) to [bend left] (Right-5.5-|Right-1) ; 
  \draw [->] (Left-5.5-|Left-last) to [bend left] (Right-9.5-|Right-1) ; 
\end{tikzpicture}

\end{document}

You need several compilations (because of the PGF/Tikz nodes).