答案1
一个例子:
\documentclass[margin=5mm]{standalone}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{array}
\usepackage{booktabs}
\usepackage{multirow}
\usepackage{siunitx}
\begin{document}
\begin{tabular}{crSSS}
& & & \multicolumn{2}{c}{Avg min cost} \\
\cmidrule{4-5}
& {$t$} & {$P_{win}$} & {random search} & {grid search} \\
\toprule
\multirow{4}{*}{$C_1$}
& $10$ & 0.34 & 100.2 & {N/A} \\
& $50$ & 1.34 & -0.00002 & \\
& $100$ & -7.3 & {---} & 123.2 \\
& $1000$ & 1300 & 14 & .34 \\
\midrule
\multirow{4}{*}{$C_2$}
& $10$ & & & \\
& $50$ & & & \\
& $100$ & & & \\
& $1000$ & & & \\
\midrule
\multirow{4}{*}{$C_3$}
& $10$ & & & \\
& $50$ & & & \\
& $100$ & & & \\
& $1000$ & & & \\
\bottomrule
\end{tabular}
\end{document}