Update Dijkstra's algorithm to use VertexMap

src/algorithms.rs

@@ -1,6 +1,7 @@
 use std::cmp::Ordering;
 use std::collections::BinaryHeap;
 
+use crate::maps::VertexMap;
 use crate::traits::GraphTopology;
 
 #[derive(PartialEq, Eq)]
@@ -21,19 +22,18 @@ impl<V: Eq> Ord for DistanceOrderedVertex<V> {
     }
 }
 
-pub struct DijkstraResult<V> {
-    pub distances: Vec<Option<u32>>,
-    pub predecessors: Vec<Option<V>>,
+pub struct DijkstraResult<V: Copy> {
+    pub distances: VertexMap<V, Option<u32>>,
+    pub predecessors: VertexMap<V, Option<V>>,
 }
 
 pub fn dijkstra<G>(graph: &G, source: G::Vertex) -> DijkstraResult<G::Vertex>
 where
     G: GraphTopology,
-    G::Vertex: Into<usize>,
 {
-    let mut predecessors = vec![None; graph.vertex_count()];
+    let mut predecessors = graph.vertex_map(None);
     let distances = dijkstra_impl(graph, source, |neighbor, predecessor| {
-        predecessors[neighbor.into()] = Some(predecessor);
+        predecessors[neighbor] = Some(predecessor);
     });
     DijkstraResult {
         distances,
@@ -41,25 +41,27 @@ where
     }
 }
 
-pub fn dijkstra_distances<G>(graph: &G, source: G::Vertex) -> Vec<Option<u32>>
+pub fn dijkstra_distances<G>(graph: &G, source: G::Vertex) -> VertexMap<G::Vertex, Option<u32>>
 where
     G: GraphTopology,
-    G::Vertex: Into<usize>,
 {
     dijkstra_impl(graph, source, |_, _| {})
 }
 
-// TODO: Replace Vec storage with VertexMap, this should make the bound on G::Vertex here obsolete.
-fn dijkstra_impl<G, F>(graph: &G, source: G::Vertex, mut on_relax: F) -> Vec<Option<u32>>
+// TODO: Add a way to provide custom edge weights for Dijkstra's algorithm.
+fn dijkstra_impl<G, F>(
+    graph: &G,
+    source: G::Vertex,
+    mut on_relax: F,
+) -> VertexMap<G::Vertex, Option<u32>>
 where
     G: GraphTopology,
-    G::Vertex: Into<usize>,
     F: FnMut(G::Vertex, G::Vertex),
 {
-    let mut distances = vec![None; graph.vertex_count()];
+    let mut distances = graph.vertex_map(None);
     let mut heap = BinaryHeap::new();
 
-    distances[source.into()] = Some(0);
+    distances[source] = Some(0);
     heap.push(DistanceOrderedVertex {
         vertex: source,
         distance: 0,
@@ -67,15 +69,14 @@ where
 
     while let Some(v) = heap.pop() {
         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 = distances[v.vertex].unwrap() + edge_weight;
+            if match distances[neighbor] {
                 None => true,
                 Some(old_distance) if old_distance > new_distance => true,
                 _ => false,
             } {
-                distances[neighbor.into()] = Some(new_distance);
+                distances[neighbor] = Some(new_distance);
                 on_relax(neighbor, v.vertex);
                 heap.push(DistanceOrderedVertex {
                     vertex: neighbor,