documentclass{article}
usepackage[utf8]{inputenc}
usepackage{listings}

begin{document}


begin{minipage}[t]{.4textwidth}
begin{lstlisting}[numbers=left]
for (i in 1..n):
  unaligned code
end{lstlisting}
end{minipage}
$rightarrow$hfill
begin{minipage}[t]{.4textwidth}
begin{lstlisting}[numbers=left]
for (i in 1..n):
  unaligned code
  ...
  ...
end{lstlisting}
end{minipage}

end{document}