% This is a TikZ implementation of the extended Dynkin diagram for the class Cn.
% The numbering follows the one used by LiE (http://http://wwwmathlabo.univ-poitiers.fr/~maavl/LiE/).
% The highest root is denoted by \star or \gamma_{\star} and has a different colour.
%
%  You'll need to load the following packages
%% \usepackage{tikz}
%% \usetikzlibrary{calc}   % this is needed in order to be able to do coordinate calculations
%% \usetikzlibrary{topaths}
%% \usetikzlibrary{decorations}
%% \usetikzlibrary{decorations.pathmorphing}
%
% Feel free to use it whereever you like, but please leave my name in the drawing.
% 
% 08/04/2015, P. Meessen 
\begin{center}
   \begin{tikzpicture}[scale=.7]
    %draw the background coordinate-grid, clearly not needed when finished
    %\draw[step=.5cm,color=gray] (0,0) node[anchor=north east] {$(0,0)$} grid (15,5) node[anchor=south west] {$(15,5)$};
    %% Draw the part for the highest root
    \fill[green!51!blue] (0,2) circle (7pt);
    \draw (0,1.4) node[color=green!51!blue] {$\star$};
    \draw[color=green!51!blue, line width=1pt] (0,2.2) -- (2,2.2);
    \draw[color=green!51!blue, line width=1pt] (0,1.8) -- (2,1.8);
    \draw[color=green!51!blue, line width=1pt] (0.9,1.6) -- (1.1,2) -- (0.9,2.4);
    %% Draw the horizontal roots
    \fill[black] (2,2) circle (7pt);
    \fill[black] (4,2) circle (7pt);
    \fill[black] (7,2) circle (7pt);
    \fill[black] (9,2) circle (7pt);
    \fill[black] (11,2) circle (7pt);
    %% Draw the lines connecting the horizontal roots
   \draw[color=black, line width=1pt] (2,2) -- (4,2);
   \draw[color=black, line width=1pt, dashed] (4,2) -- (7,2);
   \draw[color=black, line width=1pt] (7,2) -- (9,2);
   \draw[color=black, line width=1pt] (9,2.2) -- (11,2.2);
   \draw[color=black, line width=1pt] (9,1.8) -- (11,1.8);
   \draw[color=black, line width=1pt] (10.1,1.6) -- (9.9,2) -- (10.1,2.4);
   %% Put the labels
   \draw (2,1.4) node[color=black] {$1$};
   \draw (4,1.4) node[color=black] {$2$};
   \draw (7,1.4) node[color=black] {$n-2$};
   \draw (9,1.4) node[color=black] {$n-1$};
   \draw (11,1.4) node[color=black] {$n$};
   %% Indicate that this Dynkin diagram is for c_n
   \draw (3,3) node[color=black] {$\mathfrak{c}_{n}$};
   \end{tikzpicture}
\end{center}