Add GraphTopology trait and use it to interface graph model with algorithm

src/traits.rs

@@ -0,0 +1,12 @@
+pub trait GraphTopology {
+    type Vertex: Copy + Eq;
+
+    fn vertex_count(&self) -> usize;
+    fn edge_count(&self) -> usize;
+    fn degree(&self, v: Self::Vertex) -> usize;
+    fn are_adjacent(&self, v1: Self::Vertex, v2: Self::Vertex) -> bool;
+    fn vertices(&self) -> impl Iterator<Item = Self::Vertex>;
+    fn neighbors(&self, v: Self::Vertex) -> impl Iterator<Item = Self::Vertex>;
+    fn add_vertex(&mut self) -> Self::Vertex;
+    fn add_edge(&mut self, v1: Self::Vertex, v2: Self::Vertex);
+}