Drawing a graph using the PG 3.0 graphdrawing library

PGF 3.0 offers a new convenient and capable library for drawing graphs. The so called graphdrawin library requires compiling via LuaTeX.

The code was written by Mark Wibrow and published on TeX.SE.

Edit and compile if you like:

% Drawing a graph using the PG 3.0 graphdrawing library
% Author: Mark Wibrow
\documentclass[tikz,border=10pt]{standalone}
\usetikzlibrary{graphdrawing}
\usetikzlibrary{graphs}
\usegdlibrary{trees}
\begin{document}
\begin{tikzpicture}[>=stealth, every node/.style={circle, draw, minimum size=0.75cm}]
\graph [tree layout, grow=down, fresh nodes, level distance=0.5in, sibling distance=0.5in]
    {
        4 -> { 
          3 -> { 1 -> { 5, " " }, 2,2 },
          3 -> { 1, 2, 2 },
          3 -> { 1, 2, 2 }
        } 
    };
\end{tikzpicture}
\end{document}