答案1
\documentclass{article}
\usepackage{lipsum}
\begin{document}
{
% make sure there is space on the last line
\parfillskip=.5\textwidth plus .3\textwidth
\lipsum[1]
}
\vspace{\dimexpr-\parskip-\baselineskip\relax}
{\raggedleft
% make sure there is space on the first line
\noindent\hspace*{\dimexpr.5\textwidth+2em}%
\lipsum[2]
}
\end{document}