Add iterator over vertices Graph::iter()

src/models.rs

@@ -24,7 +24,6 @@ pub struct Graph {
     pub incidence_vertices: Vec<Vertex>,
 }
 
-// TODO: Add iterator of vertices.
 // TODO: Add iterator of edges.
 // TODO: Add iterator of vertex neighbors, see 'fn add_adjacent()'.
 impl Graph {
@@ -87,6 +86,10 @@ impl Graph {
         self.incidence_headers[v1.0].first_incidence =
             Some(Incidence(self.incidence_vertices.len() - 1));
     }
+
+    pub fn iter(&self) -> impl Iterator<Item = Vertex> {
+        (0..self.incidence_headers.len()).map(Vertex)
+    }
 }
 
 #[cfg(test)]