algorithm2e style comments in algorithmicx

Question

I want to use \tcc and \tcp commands in algorithmicx package.

Is there any way to do this?

\documentclass[12pt,a4paper]{report}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{enumerate}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}

\usepackage{etoolbox}
\begin{document}
\begin{figure}

\begin{algorithmic}[1]
\Procedure{Euclid}{$a,b$}\Comment{The g.c.d. of a and b}
\State $r\gets a\bmod b$
\While{$r\not=0$}\Comment{/*We have the answer if r is 0*/} %%%I want the comment in a separate line and italic.
\State $a\gets b$
\State $b\gets r$
\State $r\gets a\bmod b$

\EndWhile\label{euclidendwhile}
\State \textbf{return} $b$\Comment{The gcd is b}
\EndProcedure
\end{algorithmic}
\caption{Euclid’s algorithm}\label{euclid}
\end{figure}
\end{document}

Answer 1

In answer to your commented request in the code, create something like \LineComment{<comment>}, which will set a comment right-aligned and italicized:

\documentclass{article}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}
\newcommand{\LineComment}[1]{\Statex \hfill\textit{#1}}

\begin{document}
\begin{algorithm}
  \begin{algorithmic}[1]
  \Procedure{Euclid}{$a,b$}\Comment{The g.c.d.\ of~$a$ and~$b$}
    \State $r \gets a \bmod b$
    \While{$r \neq 0$}\LineComment{We have the answer if~$r$ is~$0$}
      \State $a \gets b$
      \State $b \gets r$
      \State $r \gets a \bmod b$
    \EndWhile\label{euclidendwhile}
    \State \textbf{return} $b$\Comment{The g.c.d.\ is~$b$}
  \EndProcedure
  \end{algorithmic}
  \caption{Euclid’s algorithm}\label{euclid}
\end{algorithm}
\end{document}

You can format \LineComment the way you want. For example, using

\newcommand{\LineComment}[1]{\Statex \hfill/* \textit{#} */}

would wrap the line comment in /*...*/:

Following some guidelines in Using end-of-line delimiter in plain TeX macro, you could also use

\makeatletter
\let\fslash=/
\catcode`\/=\active
\newcommand{/}{\@ifnextchar/{\begingroup\catcode`\^^M=12 \fslash@}\fslash}
{\catcode`\^^M=12 %
 \gdef\fslash@/#1^^M{\hfill \fslash\fslash{\itshape#1}\endgroup}}
\makeatother

in order to make / active. If used in succession //, it captures the contents until the end-of-line character is reached, placing it in an italicized font:

\documentclass{article}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}
\newcommand{\LineComment}[1]{\Statex \hfill/* \textit{#1} */}

% https://tex.stackexchange.com/q/125549/5764
\makeatletter
\let\fslash=/
\catcode`\/=\active
\newcommand{/}{\@ifnextchar/{\begingroup\catcode`\^^M=12 \fslash@}\fslash}
{\catcode`\^^M=12 %
 \gdef\fslash@/#1^^M{\hfill \fslash\fslash{\itshape#1}\endgroup}}
\makeatother

\begin{document}
\begin{algorithm}
  \begin{algorithmic}[1]
  \Procedure{Euclid}{$a,b$}\Comment{The g.c.d.\ of~$a$ and~$b$}
    \State $r \gets a \bmod b$
    \While{$r \neq 0$}\LineComment{We have the answer if~$r$ is~$0$}
      \State $a \gets b$ // Another comment
      \State $b \gets r$
      \State $r \gets a \bmod b$
    \EndWhile\label{euclidendwhile}
    \State \textbf{return} $b$\Comment{The g.c.d.\ is~$b$}
  \EndProcedure
  \end{algorithmic}
  \caption{Euclid’s algorithm}\label{euclid}
\end{algorithm}
\end{document}

The above momentary redefinition of ^^M (the end-of-line char) could be problematic, but really depends on the circumstances. Regardless, the following might be safer:

\usepackage{etoolbox}
\makeatletter
\let\fslash=/
\catcode`\/=\active
\newcommand{/}{\@ifnextchar/{\fslash@}\fslash}
\def\fslash@/{\hfill \fslash\fslash\itshape}
\AtBeginEnvironment{algorithmic}{%
  \let\olditem\item
  \renewcommand{\item}{\upshape\olditem}
}
\makeatother