src/algorithms.rs

@@ -21,19 +21,25 @@ impl<V: Eq> Ord for DistanceOrderedVertex<V> {
     }
 }
 
-// TODO: Maybe introduce a return struct type for Dijkstra's algorithm?
+pub struct DijkstraResult<V> {
+    pub distances: Vec<Option<u32>>,
+    pub predecessors: Vec<Option<V>>,
+}
+
 // TODO: Maybe variant of Dijkstra's algorithm without predecessors?
 // TODO: Replace Vec storage with VertexMap, this should make the bound on G::Vertex here obsolete.
-pub fn dijkstra<G>(graph: &G, source: G::Vertex) -> (Vec<Option<u32>>, Vec<Option<G::Vertex>>)
+pub fn dijkstra<G>(graph: &G, source: G::Vertex) -> DijkstraResult<G::Vertex>
 where
     G: GraphTopology,
     G::Vertex: Into<usize>,
 {
-    let mut distances = vec![None; graph.vertex_count()];
-    let mut predecessors = vec![None; graph.vertex_count()];
+    let mut result = DijkstraResult {
+        distances: vec![None; graph.vertex_count()],
+        predecessors: vec![None; graph.vertex_count()],
+    };
     let mut heap = BinaryHeap::new();
 
-    distances[source.into()] = Some(0);
+    result.distances[source.into()] = Some(0);
     heap.push(DistanceOrderedVertex {
         vertex: source,
         distance: 0,
@@ -43,14 +49,14 @@ where
         for neighbor in graph.neighbors(v.vertex) {
             // TODO: Add a way to provide custom edge weights for Dijkstra's algorithm.
             let edge_weight = 1;
-            let new_distance = distances[v.vertex.into()].unwrap() + edge_weight;
-            if match distances[neighbor.into()] {
+            let new_distance = result.distances[v.vertex.into()].unwrap() + edge_weight;
+            if match result.distances[neighbor.into()] {
                 None => true,
                 Some(old_distance) if old_distance > new_distance => true,
                 _ => false,
             } {
-                distances[neighbor.into()] = Some(new_distance);
-                predecessors[neighbor.into()] = Some(v.vertex);
+                result.distances[neighbor.into()] = Some(new_distance);
+                result.predecessors[neighbor.into()] = Some(v.vertex);
                 heap.push(DistanceOrderedVertex {
                     vertex: neighbor,
                     distance: new_distance,
@@ -58,5 +64,5 @@ where
             }
         }
     }
-    (distances, predecessors)
+    result
 }

tests/dijkstra.rs

@@ -6,24 +6,24 @@ use grapherity::traits::GraphTopology;
 fn dijkstra_single_vertex() {
     let mut graph = AppendGraph::new();
     let v1 = graph.add_vertex();
-    let (distances, predecessors) = algorithms::dijkstra(&graph, v1);
+    let result = algorithms::dijkstra(&graph, v1);
     assert_eq!(
-        distances.len(),
+        result.distances.len(),
         1,
         "distances count must equal vertex count"
     );
     assert_eq!(
-        predecessors.len(),
+        result.predecessors.len(),
         1,
         "predecessors count must equal vertex count"
     );
     assert_eq!(
-        distances[0],
+        result.distances[0],
         Some(0),
         "unexpected distance of source vertex"
     );
     assert_eq!(
-        predecessors[0], None,
+        result.predecessors[0], None,
         "unexpected predecessor of source vertex",
     );
 }
@@ -33,23 +33,23 @@ fn dijkstra_disconnected() {
     let mut graph = AppendGraph::new();
     let v1 = graph.add_vertex();
     graph.add_vertex();
-    let (distances, predecessors) = algorithms::dijkstra(&graph, v1);
+    let result = algorithms::dijkstra(&graph, v1);
     assert_eq!(
-        distances.len(),
+        result.distances.len(),
         2,
         "distances count must equal vertex count"
     );
     assert_eq!(
-        predecessors.len(),
+        result.predecessors.len(),
         2,
         "predecessors count must equal vertex count"
     );
     assert_eq!(
-        distances[1], None,
+        result.distances[1], None,
         "unexpected distance of disconnected vertex"
     );
     assert_eq!(
-        predecessors[0], None,
+        result.predecessors[0], None,
         "unexpected predecessor of disconnected vertex",
     );
 }
@@ -57,7 +57,7 @@ fn dijkstra_disconnected() {
 #[test]
 fn dijkstra() {
     let (graph, vertices) = make_test_graph();
-    let (distances, predecessors) = algorithms::dijkstra(&graph, vertices[0]);
+    let result = algorithms::dijkstra(&graph, vertices[0]);
     let expected_distances_from_v0 = [
         Some(0),
         Some(1),
@@ -83,25 +83,25 @@ fn dijkstra() {
         vec![Some(vertices[5]), Some(vertices[6]), Some(vertices[7])],
     ];
     assert_eq!(
-        distances.len(),
+        result.distances.len(),
         graph.vertex_count(),
         "distances count must equal vertex count"
     );
     assert_eq!(
-        predecessors.len(),
+        result.predecessors.len(),
         graph.vertex_count(),
         "predecessors count must equal vertex count"
     );
     for i in 0..graph.vertex_count() {
         assert_eq!(
-            distances[i], expected_distances_from_v0[i],
+            result.distances[i], expected_distances_from_v0[i],
             "unexpected distance from {:?} to {:?}",
             vertices[0], vertices[i]
         );
         assert!(
-            expected_predecessors_from_v0[i].contains(&predecessors[i]),
+            expected_predecessors_from_v0[i].contains(&result.predecessors[i]),
             "unexpected predecessor {:?} of {:?}",
-            predecessors[i],
+            result.predecessors[i],
             vertices[i]
         );
     }