Proper line numbering of algorithm2e when tabular environment is inside an algorithm environment

Question

I use tabular inside algorithm environment of algorithm2e package (see figure below) in order to align two columns of comment lines. Without using a table, achieving this task is difficult with some other methods suggested here.

\documentclass{article}
\usepackage{amsmath}
\usepackage[vlined, ruled, noend]{algorithm2e}

\begin{document}
\begin{algorithm}
    \LinesNumbered

    \SetKwInOut{Input}{Input}
    \SetKwInOut{Output}{Output}

    \Input{$A$}
    \Output{$C$}

    \BlankLine

    \If {condition}{
        \begin{tabular}{@{\hspace{0em}}p{0.3\linewidth}p{0.4\linewidth}l}
            \noalign{\vskip2pt}
            $B \gets A$ & Comments & Flops \\
            $C \gets B$ & Comments & Flops \\
            \multicolumn{3}{@{\hspace{0em}}l}{\KwRet $C$} \\
        \end{tabular}
    }
    \caption{Computing $C$}
\end{algorithm}
\end{document}

Despite the convenient of using a table, its downside is that the algorithm environment count each table as one line. For example, in the above figure, all three rows of the table are counted as line 2. Is there any way to modify line counter of algorithm2e to count table rows?

Answer 1

Based on your example, you can just place the elements in boxes of fixed width and they should align as needed:

\documentclass{article}

\usepackage{amsmath}
\usepackage[vlined, ruled, noend]{algorithm2e}

\begin{document}

\begin{algorithm}
  \LinesNumbered

  \SetKwInOut{Input}{Input}
  \SetKwInOut{Output}{Output}

  \Input{$A$}
  \Output{$C$}

  \BlankLine

  \If {condition}{
    \begin{tabular}{@{\hspace{0em}}p{0.3\linewidth}p{0.4\linewidth}l}
      \noalign{\vskip2pt}
        $B \gets A$ & Comments & Flops \\
        $C \gets B$ & Comments & Flops \\
        \multicolumn{3}{@{\hspace{0em}}l}{\KwRet $C$} \\
      \end{tabular}
  }
  \caption{Original: Computing $C$}
\end{algorithm}

\begin{algorithm}
  \LinesNumbered
  \DontPrintSemicolon

  \SetKwInOut{Input}{Input}
  \SetKwInOut{Output}{Output}

  \Input{$A$}
  \Output{$C$}

  \BlankLine

  \If {condition}{
    \makebox[0.3\linewidth][l]{$B \gets A$}%
      \makebox[0.4\linewidth][l]{Comments}%
      Flops\;
    \makebox[0.3\linewidth][l]{$C \gets B$}%
      \makebox[0.4\linewidth][l]{Comments}%
      Flops\;
    \KwRet $C$\;
  }
  \caption{Updated: Computing $C$}
\end{algorithm}

\end{document}