List elements without indentation

Question

I am using the enumitem package to tweak the enumerate environment. I would like to have all the items in different levels aligned in the left margin. I tried with different parameters of the package unsuccesfully. I also need to align the sentences in the items.

a.     iten1
b.     item2
b.1.   item3
c.     item 4

Any suggestion?

Answer 1

Here's a solution that typesets the labels in the margin:

\documentclass{article}

\usepackage{enumitem}

\setlist[enumerate]{align=left,leftmargin=0pt,labelsep=0pt,labelwidth=3em}
\setlist[enumerate,1]{label=\alph*.}
\setlist[enumerate,2]{label*=\arabic*.}

\usepackage{lipsum}

\begin{document}

\lipsum[1]

\begin{enumerate}
\item First
\item Second
  \begin{enumerate}
  \item Second-first
  \end{enumerate}
\item Third
\end{enumerate}

\end{document}

Addding itemindent=3em to the example above will make the labels left-aligned at the left margin:

\documentclass{article}

\usepackage{enumitem}

\setlist[enumerate]{align=left,leftmargin=0pt,labelsep=0pt,labelwidth=3em,itemindent=3em}
\setlist[enumerate,1]{label=\alph*.}
\setlist[enumerate,2]{label*=\arabic*.}

\usepackage{lipsum}

\begin{document}

\lipsum[1]

\begin{enumerate}
\item First
\item Second
  \begin{enumerate}
  \item Second-first
  \end{enumerate}
\item Third
\end{enumerate}

\end{document}