Add Dijkstra variant without returning predecessors

tests/dijkstra.rs

@@ -107,6 +107,55 @@ fn dijkstra() {
     }
 }
 
+#[test]
+fn dijkstra_distances_single_vertex() {
+    let mut graph = AppendGraph::new();
+    let v1 = graph.add_vertex();
+    let distances = algorithms::dijkstra_distances(&graph, v1);
+    assert_eq!(distances.len(), 1, "distances count must equal vertex count");
+    assert_eq!(distances[0], Some(0), "unexpected distance of source vertex");
+}
+
+#[test]
+fn dijkstra_distances_disconnected() {
+    let mut graph = AppendGraph::new();
+    let v1 = graph.add_vertex();
+    graph.add_vertex();
+    let distances = algorithms::dijkstra_distances(&graph, v1);
+    assert_eq!(distances.len(), 2, "distances count must equal vertex count");
+    assert_eq!(distances[1], None, "unexpected distance of disconnected vertex");
+}
+
+#[test]
+fn dijkstra_distances() {
+    let (graph, vertices) = make_test_graph();
+    let distances = algorithms::dijkstra_distances(&graph, vertices[0]);
+    let expected_distances_from_v0 = [
+        Some(0),
+        Some(1),
+        Some(2),
+        Some(2),
+        Some(2),
+        Some(3),
+        Some(3),
+        Some(3),
+        Some(3),
+        Some(4),
+    ];
+    assert_eq!(
+        distances.len(),
+        graph.vertex_count(),
+        "distances count must equal vertex count"
+    );
+    for i in 0..graph.vertex_count() {
+        assert_eq!(
+            distances[i], expected_distances_from_v0[i],
+            "unexpected distance from {:?} to {:?}",
+            vertices[0], vertices[i]
+        );
+    }
+}
+
 fn make_test_graph() -> (AppendGraph, [<AppendGraph as GraphTopology>::Vertex; 10]) {
     let mut graph = AppendGraph::new();
     let vertices = core::array::from_fn::<_, 10, _>(|_| graph.add_vertex());