{ \newcommand{\nodea}{\node[draw,circle] (a) {$0$}
;}\newcommand{\nodeb}{\node (b) {$t_1$}
;}\newcommand{\nodec}{\node (c) {$t_k$}
;}\newcommand{\noded}{\node (d) {$...$}
;}\begin{tikzpicture}[auto]
\matrix[column sep=.3cm, row sep=.3cm,ampersand replacement=\&]{
         \& \nodea  \&         \\ 
 \nodeb  \& \noded     \& \nodec  \\
};

\path[ultra thick, red] (a) edge (b) edge (c);
\path[dashed, red] (a) edge (d);
\end{tikzpicture}}