tabular columns too wide

Modify the length \tabcolsep to compress the table horizontally.

\documentclass[smaller]{beamer}
\usepackage[T1]{fontenc}
\usepackage{fix-cm}

\setlength{\tabcolsep}{2pt}

\begin{document}
  \begin{frame}
    \begin{tabular}{|*{26}{c|}}
      A & B & C & D & E & F & G & H & I & J & K & L & M & N & O & P & Q & R & S & T & U & V & W &   X & Y & Z \\
      G & T & U & J & C & P & L & D & O & R & Y & W & X & Z & F & I & V & Q & S & K & A & N & E & M & H & B \\
    \end{tabular}
  \end{frame}
\end{document}

\documentclass{beamer}
\begin{document}
  \begin{frame}
  \resizebox{\linewidth} {\height}{%
    \setlength\tabcolsep{2pt}%
    \begin{tabular}{|*{26}{c|}}
      A & B & C & D & E & F & G & H & I & J & K & L & M & N & O & P & Q & R & S & T & U & V & W &   X & Y & Z \\
      G & T & U & J & C & P & L & D & O & R & Y & W & X & Z & F & I & V & Q & S & K & A & N & E & M & H & B \\
    \end{tabular}}
  \end{frame}
\end{document}