documentclass{scrartcl}
usepackage[utf8]{inputenc}
usepackage{tikz}
usetikzlibrary{automata,positioning,arrows,matrix,backgrounds,calc}
usetikzlibrary{decorations.text}
usetikzlibrary{decorations.pathmorphing}

tikzset{
    node_standard/.style = {
        ->,>=stealth',shorten >=1pt,node distance=2.5cm,auto,thick,
        main node/.style={circle,fill=gray!25,draw,font=sffamilyLargebfseries},
        black node/.style={circle,fill=black,text=white,draw,font=sffamilyLargebfseries}
    }
}

begin{document}
begin{center}
    begin{tikzpicture} [node_standard, node distance=2cm]%

        node[main node] (1)            {$s$};
        node[main node] (2) at (2cm,1cm)       {};
        node[black node] (3) at (1.6cm,-1cm)   {$u$};
        node[main node] (4) [below right of=2] {$t$};

        path[path_standard]
        (2) edge        node    {}  (1)
        (2) edge        node    {}  (4)
        (3) edge        node    {}  (1)
            edge        node    {}  (2)
        (4) edge        node    {}  (3);

    end{tikzpicture}
     \
     \
    ole ole ole
end{center}
end{document}