调整表格中行组之间的规则粗细

Question

如何才能使 A 组和 B 组之间的水平线更粗，而不会干扰括号？为了实现这一点，我是否需要使用其他方法来获取括号？

\documentclass[11pt]{article}
\usepackage{amsmath,tabularx,ragged2e}
\newcolumntype{C}[1]{>{\Centering}m{#1}}

\begin{document}

\[
\begin{array}{r}
    \begin{tabular}{|C{24pt}!{\vrule width1pt}C{20pt}|C{20pt}|}
    \hline
    a&b&c\\ \noalign{\hrule height1pt}
    \end{tabular}\\
    \llap{\hbox{group A}}
    \left\{
        \begin{tabular}{|C{24pt}!{\vrule width1pt}C{20pt}|C{20pt}|}
            1&2&3\\\hline
            4&5&6\\\hline
        \end{tabular}
    \right.\kern-\nulldelimiterspace\\
    \llap{\hbox{group B}}
    \left\{
    \begin{tabular}{|C{24pt}!{\vrule width1pt}C{20pt}|C{20pt}|}
        7&8&9\\\hline
        7&8&9\\\hline
    \end{tabular}
    \right.\kern-\nulldelimiterspace
\end{array}
\]

\end{document}

Answer 1

使用包Xhline中定义的makecell：

\documentclass[11pt]{article}
\usepackage{amsmath}
\usepackage{ragged2e}
\usepackage{makecell,tabularx}  % <---
\newcolumntype{C}[1]{>{\Centering}m{#1}}

\begin{document}

\[
    \begin{array}{r}
\begin{tabular}{|C{24pt}!{\vrule width1pt}C{20pt}|C{20pt}|}\hline
a&b&c\\
    \Xhline{1pt}   % <---
\end{tabular}\\
\llap{\hbox{group A}}\left\{\begin{tabular}{|C{24pt}!{\vrule width1pt}C{20pt}|C{20pt}|}
1&2&3\\ \hline
4&5&6\\ \Xhline{1pt}   % <---
\end{tabular}\right.\kern-\nulldelimiterspace\\

\llap{\hbox{group B}}\left\{\begin{tabular}{|C{24pt}!{\vrule width1pt}C{20pt}|C{20pt}|}
7&8&9\\\hline
7&8&9\\\hline
\end{tabular}\right.\kern-\nulldelimiterspace
    \end{array}
\]

\end{document}