Graph Properties / Features

4. The length of a path is the number of edges (not the number of vertices) used in the path.
   

   The path $1,2,3$ contains two edges: $\{1,2\}$ and $\{2,3\}$. Therefore, its length is $2$. Miriam Briskman, CC BY-NC 4.0.

   \documentclass[border=1pt]{standalone}
   \usepackage{tikz}
   
   \tikzset{
   vertex/.style={draw, circle, very thick, minimum size=1cm},
   edge/.style={very thick}
   }
   
   \begin{document}
   
   \begin{tikzpicture}
   
   \node[vertex] (1) at (0,0) {$1$};
   \node[vertex] (2) at (2,0) {$2$};
   \node[vertex] (3) at (4,0) {$3$};
   
   \draw[edge] (1) -- (2);
   \draw[edge] (2) -- (3);
   
   \end{tikzpicture}
   
   \end{document}