Align tabular cells at plus or minus signs
Removing the intercolumn space and using math mode
\documentclass{article}
\usepackage{array,booktabs}
\begin{document}
\begin{table}
\begin{tabular}{l*{3}{>{$}r<{$}@{}>{$}l<{$}}>{$}l<{$}}
\toprule
Examples & \multicolumn{2}{l}{value1} & \multicolumn{2}{l}{value2} & \multicolumn{3}{l}{value3 (+smth)} \\
example1 & 1 & -1 & 12 & +? & 12 & +? & (+123) \\
example2 & 12 & +5 & 123 & +? & 123 & +? & (+12) \\
example3 & 123 & -10 & 1 & +? & 1 & +? & (+1234) \\
example4 & 23 & +123 & 234 & +? & 234 & +? & (+23) \\
example5 & 234 & +4 & 23 & +? & 23 & +? & (+234) \\
\bottomrule
\end{tabular}
\end{table}
\end{document}
You have three composite columns with the following pattern: number
±
number
, this can be set up as @{}>{${}}c<{{}$}@{}
. A new column type can be handy for this, see below. I would also combine the last column with the previous one to be similar to their header.
\documentclass{article}
\usepackage{array,booktabs}
\begin{document}
\begin{table}
\newcolumntype{C}{ @{}>{${}}c<{{}$}@{} }
\begin{tabular}{l *3{rCl} }
\toprule
Examples & \multicolumn{3}{c}{value1} & \multicolumn{3}{c}{value2} & \multicolumn{4}{c}{value3 (+smth)} \\
example1 & 1 & - & 1 & 12 & + & ? & 12 & + & ? (+123) \\
example2 & 12 & + & 5 & 123 & + & ? & 123 & + & ? (+12) \\
example3 & 123 & - & 10 & 1 & + & ? & 1 & + & ? (+1234) \\
example4 & 23 & + & 123 & 234 & + & ? & 234 & + & ? (+23) \\
example5 & 234 & + & 4 & 23 & + & ? & 23 & + & ? (+234) \\ \bottomrule
\end{tabular}
\end{table}
\end{document}